924 lines
21 KiB
Plaintext
924 lines
21 KiB
Plaintext
.\" Copyright (c) 1979 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)pxin2.n 5.2 (Berkeley) 4/17/91
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.\"
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.if !\n(xx .so tmac.p
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.nr H1 1
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.if n .ND
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.NH
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Operations
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.NH 2
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Naming conventions and operation summary
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.PP
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Table 2.1 outlines the opcode typing convention.
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The expression ``a above b'' means that `a' is on top
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of the stack with `b' below it.
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Table 2.3 describes each of the opcodes.
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The character `*' at the end of a name specifies that
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all operations with the root prefix
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before the `*'
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are summarized by one entry.
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Table 2.2 gives the codes used
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to describe the type inline data expected by each instruction.
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.sp 2
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.so table2.1.n
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.sp 2
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.so table2.2.n
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.bp
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.so table2.3.n
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.bp
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.NH 2
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Basic control operations
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.LP
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.SH
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HALT
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.IP
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Corresponds to the Pascal procedure
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.I halt ;
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causes execution to end with a post-mortem backtrace as if a run-time
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error had occurred.
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.SH
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BEG s,W,w,"
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.IP
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Causes the second part of the block mark to be created, and
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.I W
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bytes of local variable space to be allocated and cleared to zero.
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Stack overflow is detected here.
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.I w
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is the first line of the body of this section for error traceback,
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and the inline string (length s) the character representation of its name.
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.SH
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NODUMP s,W,w,"
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.IP
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Equivalent to
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.SM BEG ,
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and used to begin the main program when the ``p''
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option is disabled so that the post-mortem backtrace will be inhibited.
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.SH
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END
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.IP
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Complementary to the operators
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.SM CALL
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and
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.SM BEG ,
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exits the current block, calling the procedure
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.I pclose
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to flush buffers for and release any local files.
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Restores the environment of the caller from the block mark.
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If this is the end for the main program, all files are
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.I flushed,
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and the interpreter is exited.
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.SH
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CALL l,A
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.IP
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Saves the current line number, return address, and active display entry pointer
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.I dp
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in the first part of the block mark, then transfers to the entry point
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given by the relative address
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.I A ,
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that is the beginning of a
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.B procedure
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or
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.B function
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at level
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.I l.
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.SH
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PUSH s
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.IP
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Clears
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.I s
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bytes on the stack.
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Used to make space for the return value of a
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.B function
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just before calling it.
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.SH
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POP s
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.IP
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Pop
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.I s
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bytes off the stack.
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Used after a
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.B function
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or
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.B procedure
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returns to remove the arguments from the stack.
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.SH
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TRA a
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.IP
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Transfer control to relative address
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.I a
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as a local
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.B goto
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or part of a structured statement.
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.SH
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TRA4 A
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.IP
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Transfer control to an absolute address as part of a non-local
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.B goto
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or to branch over procedure bodies.
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.SH
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LINO s
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.IP
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Set current line number to
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.I s.
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For consistency, check that the expression stack is empty
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as it should be (as this is the start of a statement.)
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This consistency check will fail only if there is a bug in the
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interpreter or the interpreter code has somehow been damaged.
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Increment the statement count and if it exceeds the statement limit,
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generate a fault.
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.SH
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GOTO l,A
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.IP
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Transfer control to address
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.I A
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that is in the block at level
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.I l
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of the display.
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This is a non-local
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.B goto.
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Causes each block to be exited as if with
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.SM END ,
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flushing and freeing files with
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.I pclose,
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until the current display entry is at level
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.I l.
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.SH
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SDUP*
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.IP
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Duplicate the word or long on the top of
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the stack.
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This is used mostly for constructing sets.
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See section 2.11.
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.NH 2
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If and relational operators
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.SH
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IF a
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.IP
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The interpreter conditional transfers all take place using this operator
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that examines the Boolean value on the top of the stack.
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If the value is
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.I true ,
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the next code is executed,
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otherwise control transfers to the specified address.
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.SH
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REL* r
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.IP
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These take two arguments on the stack,
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and the sub-operation code specifies the relational operation to
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be done, coded as follows with `a' above `b' on the stack:
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.DS
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.mD
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.TS
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lb lb
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c a.
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Code Operation
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_
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0 a = b
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2 a <> b
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4 a < b
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6 a > b
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8 a <= b
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10 a >= b
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.TE
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.DE
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.IP
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Each operation does a test to set the condition code
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appropriately and then does an indexed branch based on the
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sub-operation code to a test of the condition here specified,
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pushing a Boolean value on the stack.
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.IP
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Consider the statement fragment:
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.DS
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.mD
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\*bif\fR a = b \*bthen\fR
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.DE
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.IP
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If
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.I a
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and
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.I b
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are integers this generates the following code:
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.DS
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.TS
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lp-2w(8) l.
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RV4:\fIl a\fR
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RV4:\fIl b\fR
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REL4 \&=
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IF \fIElse part offset\fR
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.sp
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.T&
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c s.
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\fI\&... Then part code ...\fR
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.TE
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.DE
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.NH 2
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Boolean operators
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.PP
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The Boolean operators
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.SM AND ,
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.SM OR ,
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and
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.SM NOT
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manipulate values on the top of the stack.
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All Boolean values are kept in single bytes in memory,
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or in single words on the stack.
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Zero represents a Boolean \fIfalse\fP, and one a Boolean \fItrue\fP.
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.NH 2
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Right value, constant, and assignment operators
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.SH
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LRV* l,A
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.br
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RV* l,a
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.IP
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The right value operators load values on the stack.
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They take a block number as a sub-opcode and load the appropriate
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number of bytes from that block at the offset specified
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in the following word onto the stack. As an example, consider
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.SM LRV4 :
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.DS
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.mD
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_LRV4:
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\fBcvtbl\fR (lc)+,r0 #r0 has display index
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\fBaddl3\fR _display(r0),(lc)+,r1 #r1 has variable address
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\fBpushl\fR (r1) #put value on the stack
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\fBjmp\fR (loop)
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.DE
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.IP
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Here the interpreter places the display level in r0.
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It then adds the appropriate display value to the inline offset and
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pushes the value at this location onto the stack.
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Control then returns to the main
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interpreter loop.
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The
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.SM RV*
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operators have short inline data that
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reduces the space required to address the first 32K of
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stack space in each stack frame.
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The operators
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.SM RV14
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and
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.SM RV24
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provide explicit conversion to long as the data
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is pushed.
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This saves the generation of
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.SM STOI
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to align arguments to
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.SM C
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subroutines.
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.SH
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CON* r
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.IP
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The constant operators load a value onto the stack from inline code.
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Small integer values are condensed and loaded by the
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.SM CON1
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operator, that is given by
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.DS
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.mD
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_CON1:
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\fBcvtbw\fR (lc)+,\-(sp)
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\fBjmp\fR (loop)
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.DE
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.IP
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Here note that little work was required as the required constant
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was available at (lc)+.
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For longer constants,
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.I lc
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must be incremented before moving the constant.
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The operator
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.SM CON
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takes a length specification in the sub-opcode and can be used to load
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strings and other variable length data onto the stack.
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The operators
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.SM CON14
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and
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.SM CON24
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provide explicit conversion to long as the constant is pushed.
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.SH
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AS*
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.IP
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The assignment operators are similar to arithmetic and relational operators
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in that they take two operands, both in the stack,
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but the lengths given for them specify
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first the length of the value on the stack and then the length
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of the target in memory.
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The target address in memory is under the value to be stored.
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Thus the statement
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.DS
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i := 1
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.DE
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.IP
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where
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.I i
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is a full-length, 4 byte, integer,
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will generate the code sequence
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.DS
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.TS
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lp-2w(8) l.
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LV:\fIl i\fP
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CON1:1
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AS24
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.TE
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.DE
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.IP
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Here
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.SM LV
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will load the address of
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.I i,
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that is really given as a block number in the sub-opcode and an
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offset in the following word,
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onto the stack, occupying a single word.
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.SM CON1 ,
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that is a single word instruction,
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then loads the constant 1,
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that is in its sub-opcode,
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onto the stack.
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Since there are not one byte constants on the stack,
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this becomes a 2 byte, single word integer.
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The interpreter then assigns a length 2 integer to a length 4 integer using
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.SM AS24 \&.
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The code sequence for
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.SM AS24
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is given by:
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.DS
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.mD
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_AS24:
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\fBincl\fR lc
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\fBcvtwl\fR (sp)+,*(sp)+
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\fBjmp\fR (loop)
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.DE
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.IP
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Thus the interpreter gets the single word off the stack,
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extends it to be a 4 byte integer
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gets the target address off the stack,
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and finally stores the value in the target.
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This is a typical use of the constant and assignment operators.
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.NH 2
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Addressing operations
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.SH
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LLV l,W
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.br
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LV l,w
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.IP
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The most common operation done by the interpreter
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is the ``left value'' or ``address of'' operation.
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It is given by:
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.DS
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.mD
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_LLV:
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\fBcvtbl\fR (lc)+,r0 #r0 has display index
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\fBaddl3\fR _display(r0),(lc)+,\-(sp) #push address onto the stack
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\fBjmp\fR (loop)
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.DE
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.IP
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It calculates an address in the block specified in the sub-opcode
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by adding the associated display entry to the
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offset that appears in the following word.
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The
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.SM LV
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operator has a short inline data that reduces the space
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required to address the first 32K of stack space in each call frame.
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.SH
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OFF s
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.IP
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The offset operator is used in field names.
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Thus to get the address of
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.LS
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p^.f1
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.LE
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.IP
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.I pi
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would generate the sequence
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.DS
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.mD
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.TS
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lp-2w(8) l.
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RV:\fIl p\fP
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OFF \fIf1\fP
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.TE
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.DE
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.IP
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where the
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.SM RV
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loads the value of
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.I p,
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given its block in the sub-opcode and offset in the following word,
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and the interpreter then adds the offset of the field
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.I f1
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in its record to get the correct address.
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.SM OFF
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takes its argument in the sub-opcode if it is small enough.
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.SH
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NIL
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.IP
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The example above is incomplete, lacking a check for a
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.B nil
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pointer.
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The code generated would be
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.DS
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.TS
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lp-2w(8) l.
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RV:\fIl p\fP
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NIL
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OFF \fIf1\fP
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.TE
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.DE
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.IP
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where the
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.SM NIL
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operation checks for a
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.I nil
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pointer and generates the appropriate runtime error if it is.
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.SH
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LVCON s,"
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.IP
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A pointer to the specified length inline data is pushed
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onto the stack.
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This is primarily used for
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.I printf
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type strings used by
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.SM WRITEF .
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(see sections 3.6 and 3.8)
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.SH
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INX* s,w,w
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.IP
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The operators
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.SM INX2
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and
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.SM INX4
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are used for subscripting.
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For example, the statement
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.DS
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a[i] := 2.0
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.DE
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.IP
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with
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.I i
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an integer and
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.I a
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an
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``array [1..1000] of real''
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would generate
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.DS
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.TS
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lp-2w(8) l.
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LV:\fIl a\fP
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RV4:\fIl i\fP
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INX4:8 1,999
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CON8 2.0
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AS8
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.TE
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.DE
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.IP
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Here the
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.SM LV
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operation takes the address of
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.I a
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and places it on the stack.
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The value of
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.I i
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is then placed on top of this on the stack.
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The array address is indexed by the
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length 4 index (a length 2 index would use
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.SM INX2 )
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where the individual elements have a size of 8 bytes.
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The code for
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.SM INX4
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is:
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.DS
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.mD
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_INX4:
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\fBcvtbl\fR (lc)+,r0
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\fBbneq\fR L1
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\fBcvtwl\fR (lc)+,r0 #r0 has size of records
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L1:
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\fBcvtwl\fR (lc)+,r1 #r1 has lower bound
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\fBmovzwl\fR (lc)+,r2 #r2 has upper-lower bound
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\fBsubl3\fR r1,(sp)+,r3 #r3 has base subscript
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\fBcmpl\fR r3,r2 #check for out of bounds
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\fBbgtru\fR esubscr
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\fBmull2\fR r0,r3 #calculate byte offset
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\fBaddl2\fR r3,(sp) #calculate actual address
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\fBjmp\fR (loop)
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esubscr:
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\fBmovw\fR $ESUBSCR,_perrno
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\fBjbr\fR error
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.DE
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.IP
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|
Here the lower bound is subtracted, and range checked against the
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upper minus lower bound.
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The offset is then scaled to a byte offset into the array
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and added to the base address on the stack.
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Multi-dimension subscripts are translated as a sequence of single subscriptings.
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.SH
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IND*
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.IP
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For indirect references through
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.B var
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parameters and pointers,
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the interpreter has a set of indirection operators that convert a pointer
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on the stack into a value on the stack from that address.
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|
different
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.SM IND
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|
operators are necessary because of the possibility of different
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length operands.
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|
The
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.SM IND14
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and
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.SM IND24
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|
operators do conversions to long
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as they push their data.
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.NH 2
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|
Arithmetic operators
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|
.PP
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|
The interpreter has many arithmetic operators.
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|
All operators produce results long enough to prevent overflow
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|
unless the bounds of the base type are exceeded.
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|
The basic operators available are
|
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.DS
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|
Addition: ADD*, SUCC*
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|
Subtraction: SUB*, PRED*
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Multiplication: MUL*, SQR*
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|
Division: DIV*, DVD*, MOD*
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|
Unary: NEG*, ABS*
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.DE
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.NH 2
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|
Range checking
|
|
.PP
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|
The interpreter has several range checking operators.
|
|
The important distinction among these operators is between values whose
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legal range begins at zero and those that do not begin at zero,
|
|
for example
|
|
a subrange variable whose values range from 45 to 70.
|
|
For those that begin at zero, a simpler ``logical'' comparison against
|
|
the upper bound suffices.
|
|
For others, both the low and upper bounds must be checked independently,
|
|
requiring two comparisons.
|
|
On the
|
|
.SM "VAX 11/780"
|
|
both checks are done using a single index instruction
|
|
so the only gain is in reducing the inline data.
|
|
.NH 2
|
|
Case operators
|
|
.PP
|
|
The interpreter includes three operators for
|
|
.B case
|
|
statements that are used depending on the width of the
|
|
.B case
|
|
label type.
|
|
For each width, the structure of the case data is the same, and
|
|
is represented in figure 2.4.
|
|
.sp 1
|
|
.so fig2.4.n
|
|
.PP
|
|
The
|
|
.SM CASEOP
|
|
case statement operators do a sequential search through the
|
|
case label values.
|
|
If they find the label value, they take the corresponding entry
|
|
from the transfer table and cause the interpreter to branch to the
|
|
specified statement.
|
|
If the specified label is not found, an error results.
|
|
.PP
|
|
The
|
|
.SM CASE
|
|
operators take the number of cases as a sub-opcode
|
|
if possible.
|
|
Three different operators are needed to handle single byte,
|
|
word, and long case transfer table values.
|
|
For example, the
|
|
.SM CASEOP1
|
|
operator has the following code sequence:
|
|
.DS
|
|
.mD
|
|
_CASEOP1:
|
|
\fBcvtbl\fR (lc)+,r0
|
|
\fBbneq\fR L1
|
|
\fBcvtwl\fR (lc)+,r0 #r0 has length of case table
|
|
L1:
|
|
\fBmovaw\fR (lc)[r0],r2 #r2 has pointer to case labels
|
|
\fBmovzwl\fR (sp)+,r3 #r3 has the element to find
|
|
\fBlocc\fR r3,r0,(r2) #r0 has index of located element
|
|
\fBbeql\fR caserr #element not found
|
|
\fBmnegl\fR r0,r0 #calculate new lc
|
|
\fBcvtwl\fR (r2)[r0],r1 #r1 has lc offset
|
|
\fBaddl2\fR r1,lc
|
|
\fBjmp\fR (loop)
|
|
caserr:
|
|
\fBmovw\fR $ECASE,_perrno
|
|
\fBjbr\fR error
|
|
.DE
|
|
.PP
|
|
Here the interpreter first computes the address of the beginning
|
|
of the case label value area by adding twice the number of case label
|
|
values to the address of the transfer table, since the transfer
|
|
table entries are 2 byte address offsets.
|
|
It then searches through the label values, and generates an ECASE
|
|
error if the label is not found.
|
|
If the label is found, the index of the corresponding entry
|
|
in the transfer table is extracted and that offset is added
|
|
to the interpreter location counter.
|
|
.NH 2
|
|
Operations supporting pxp
|
|
.PP
|
|
The following operations are defined to do execution profiling.
|
|
.SH
|
|
PXPBUF w
|
|
.IP
|
|
Causes the interpreter to allocate a count buffer
|
|
with
|
|
.I w
|
|
four byte counters
|
|
and to clear them to zero.
|
|
The count buffer is placed within an image of the
|
|
.I pmon.out
|
|
file as described in the
|
|
.I "PXP Implementation Notes."
|
|
The contents of this buffer are written to the file
|
|
.I pmon.out
|
|
when the program ends.
|
|
.SH
|
|
COUNT w
|
|
.IP
|
|
Increments the counter specified by
|
|
.I w .
|
|
.SH
|
|
TRACNT w,A
|
|
.IP
|
|
Used at the entry point to procedures and functions,
|
|
combining a transfer to the entry point of the block with
|
|
an incrementing of its entry count.
|
|
.NH 2
|
|
Set operations
|
|
.PP
|
|
The set operations:
|
|
union
|
|
.SM ADDT,
|
|
intersection
|
|
.SM MULT,
|
|
element removal
|
|
.SM SUBT,
|
|
and the set relationals
|
|
.SM RELT
|
|
are straightforward.
|
|
The following operations are more interesting.
|
|
.SH
|
|
CARD s
|
|
.IP
|
|
Takes the cardinality of a set of size
|
|
.I s
|
|
bytes on top of the stack, leaving a 2 byte integer count.
|
|
.SM CARD
|
|
uses the
|
|
.B ffs
|
|
opcode to successively count the number of set bits in the set.
|
|
.SH
|
|
CTTOT s,w,w
|
|
.IP
|
|
Constructs a set.
|
|
This operation requires a non-trivial amount of work,
|
|
checking bounds and setting individual bits or ranges of bits.
|
|
This operation sequence is slow,
|
|
and motivates the presence of the operator
|
|
.SM INCT
|
|
below.
|
|
The arguments to
|
|
.SM CTTOT
|
|
include the number of elements
|
|
.I s
|
|
in the constructed set,
|
|
the lower and upper bounds of the set,
|
|
the two
|
|
.I w
|
|
values,
|
|
and a pair of values on the stack for each range in the set, single
|
|
elements in constructed sets being duplicated with
|
|
.SM SDUP
|
|
to form degenerate ranges.
|
|
.SH
|
|
IN s,w,w
|
|
.IP
|
|
The operator
|
|
.B in
|
|
for sets.
|
|
The value
|
|
.I s
|
|
specifies the size of the set,
|
|
the two
|
|
.I w
|
|
values the lower and upper bounds of the set.
|
|
The value on the stack is checked to be in the set on the stack,
|
|
and a Boolean value of
|
|
.I true
|
|
or
|
|
.I false
|
|
replaces the operands.
|
|
.SH
|
|
INCT
|
|
.IP
|
|
The operator
|
|
.B in
|
|
on a constructed set without constructing it.
|
|
The left operand of
|
|
.B in
|
|
is on top of the stack followed by the number of pairs in the
|
|
constructed set,
|
|
and then the pairs themselves, all as single word integers.
|
|
Pairs designate runs of values and single values are represented by
|
|
a degenerate pair with both value equal.
|
|
This operator is generated in grammatical constructs such as
|
|
.LS
|
|
\fBif\fR character \fBin\fR [`+', '\-', `*', `/']
|
|
.LE
|
|
.IP
|
|
or
|
|
.LS
|
|
\fBif\fR character \fBin\fR [`a'..`z', `$', `_']
|
|
.LE
|
|
.IP
|
|
These constructs are common in Pascal, and
|
|
.SM INCT
|
|
makes them run much faster in the interpreter,
|
|
as if they were written as an efficient series of
|
|
.B if
|
|
statements.
|
|
.NH 2
|
|
Miscellaneous
|
|
.PP
|
|
Other miscellaneous operators that are present in the interpreter
|
|
are
|
|
.SM ASRT
|
|
that causes the program to end if the Boolean value on the stack is not
|
|
.I true,
|
|
and
|
|
.SM STOI ,
|
|
.SM STOD ,
|
|
.SM ITOD ,
|
|
and
|
|
.SM ITOS
|
|
that convert between different length arithmetic operands for
|
|
use in aligning the arguments in
|
|
.B procedure
|
|
and
|
|
.B function
|
|
calls, and with some untyped built-ins, such as
|
|
.SM SIN
|
|
and
|
|
.SM COS \&.
|
|
.PP
|
|
Finally, if the program is run with the run-time testing disabled, there
|
|
are special operators for
|
|
.B for
|
|
statements
|
|
and special indexing operators for arrays
|
|
that have individual element size that is a power of 2.
|
|
The code can run significantly faster using these operators.
|
|
.NH 2
|
|
Mathematical Functions
|
|
.PP
|
|
The transcendental functions
|
|
.SM SIN ,
|
|
.SM COS ,
|
|
.SM ATAN ,
|
|
.SM EXP ,
|
|
.SM LN ,
|
|
.SM SQRT ,
|
|
.SM SEED ,
|
|
and
|
|
.SM RANDOM
|
|
are taken from the standard UNIX
|
|
mathematical package.
|
|
These functions take double precision floating point
|
|
values and return the same.
|
|
.PP
|
|
The functions
|
|
.SM EXPO ,
|
|
.SM TRUNC ,
|
|
and
|
|
.SM ROUND
|
|
take a double precision floating point number.
|
|
.SM EXPO
|
|
returns an integer representing the machine
|
|
representation of its argument's exponent,
|
|
.SM TRUNC
|
|
returns the integer part of its argument, and
|
|
.SM ROUND
|
|
returns the rounded integer part of its argument.
|
|
.NH 2
|
|
System functions and procedures
|
|
.SH
|
|
LLIMIT
|
|
.IP
|
|
A line limit and a file pointer are passed on the stack.
|
|
If the limit is non-negative the line limit is set to the
|
|
specified value, otherwise it is set to unlimited.
|
|
The default is unlimited.
|
|
.SH
|
|
STLIM
|
|
.IP
|
|
A statement limit is passed on the stack. The statement limit
|
|
is set as specified.
|
|
The default is 500,000.
|
|
No limit is enforced when the ``p'' option is disabled.
|
|
.SH
|
|
CLCK
|
|
.br
|
|
SCLCK
|
|
.IP
|
|
.SM CLCK
|
|
returns the number of milliseconds of user time used by the program;
|
|
.SM SCLCK
|
|
returns the number of milliseconds of system time used by the program.
|
|
.SH
|
|
WCLCK
|
|
.IP
|
|
The number of seconds since some predefined time is
|
|
returned. Its primary usefulness is in determining
|
|
elapsed time and in providing a unique time stamp.
|
|
.sp
|
|
.LP
|
|
The other system time procedures are
|
|
.SM DATE
|
|
and
|
|
.SM TIME
|
|
that copy an appropriate text string into a pascal string array.
|
|
The function
|
|
.SM ARGC
|
|
returns the number of command line arguments passed to the program.
|
|
The procedure
|
|
.SM ARGV
|
|
takes an index on the stack and copies the specified
|
|
command line argument into a pascal string array.
|
|
.NH 2
|
|
Pascal procedures and functions
|
|
.SH
|
|
PACK s,w,w,w
|
|
.br
|
|
UNPACK s,w,w,w
|
|
.IP
|
|
They function as a memory to memory move with several
|
|
semantic checks.
|
|
They do no ``unpacking'' or ``packing'' in the true sense as the
|
|
interpreter supports no packed data types.
|
|
.SH
|
|
NEW s
|
|
.br
|
|
DISPOSE s
|
|
.IP
|
|
An
|
|
.SM LV
|
|
of a pointer is passed.
|
|
.SM NEW
|
|
allocates a record of a specified size and puts a pointer
|
|
to it into the pointer variable.
|
|
.SM DISPOSE
|
|
deallocates the record pointed to by the pointer
|
|
and sets the pointer to
|
|
.SM NIL .
|
|
.sp
|
|
.LP
|
|
The function
|
|
.SM CHR*
|
|
converts a suitably small integer into an ascii character.
|
|
Its primary purpose is to do a range check.
|
|
The function
|
|
.SM ODD*
|
|
returns
|
|
.I true
|
|
if its argument is odd and returns
|
|
.I false
|
|
if its argument is even.
|
|
The function
|
|
.SM UNDEF
|
|
always returns the value
|
|
.I false .
|