68 lines
2.9 KiB
Plaintext
68 lines
2.9 KiB
Plaintext
'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) proc.n 1.5 96/03/25 20:21:12
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'\"
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.so man.macros
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.TH proc n "" Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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proc \- Create a Tcl procedure
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.SH SYNOPSIS
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\fBproc \fIname args body\fR
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.BE
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.SH DESCRIPTION
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.PP
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The \fBproc\fR command creates a new Tcl procedure named
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\fIname\fR, replacing
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any existing command or procedure there may have been by that name.
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Whenever the new command is invoked, the contents of \fIbody\fR will
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be executed by the Tcl interpreter.
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\fIArgs\fR specifies the formal arguments to the
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procedure. It consists of a list, possibly empty, each of whose
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elements specifies
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one argument. Each argument specifier is also a list with either
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one or two fields. If there is only a single field in the specifier
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then it is the name of the argument; if there are two fields, then
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the first is the argument name and the second is its default value.
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.PP
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When \fIname\fR is invoked a local variable
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will be created for each of the formal arguments to the procedure; its
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value will be the value of corresponding argument in the invoking command
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or the argument's default value.
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Arguments with default values need not be
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specified in a procedure invocation. However, there must be enough
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actual arguments for all the
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formal arguments that don't have defaults, and there must not be any extra
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actual arguments. There is one special case to permit procedures with
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variable numbers of arguments. If the last formal argument has the name
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\fBargs\fR, then a call to the procedure may contain more actual arguments
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than the procedure has formals. In this case, all of the actual arguments
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starting at the one that would be assigned to \fBargs\fR are combined into
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a list (as if the \fBlist\fR command had been used); this combined value
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is assigned to the local variable \fBargs\fR.
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.PP
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When \fIbody\fR is being executed, variable names normally refer to
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local variables, which are created automatically when referenced and
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deleted when the procedure returns. One local variable is automatically
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created for each of the procedure's arguments.
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Global variables can only be accessed by invoking
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the \fBglobal\fR command or the \fBupvar\fR command.
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.PP
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The \fBproc\fR command returns an empty string. When a procedure is
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invoked, the procedure's return value is the value specified in a
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\fBreturn\fR command. If the procedure doesn't execute an explicit
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\fBreturn\fR, then its return value is the value of the last command
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executed in the procedure's body.
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If an error occurs while executing the procedure
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body, then the procedure-as-a-whole will return that same error.
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.SH KEYWORDS
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argument, procedure
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