96 lines
3.5 KiB
Groff
96 lines
3.5 KiB
Groff
'\"
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'\" Copyright (c) 1989-1993 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: @(#) CrtMathFnc.3 1.8 96/03/25 19:59:55
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'\"
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.so man.macros
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.TH Tcl_CreateMathFunc 3 7.0 Tcl "Tcl Library Procedures"
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.BS
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.SH NAME
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Tcl_CreateMathFunc \- Define a new math function for expressions
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.SH SYNOPSIS
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.nf
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\fB#include <tcl.h>\fR
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.sp
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\fBTcl_CreateMathFunc\fR(\fIinterp, name, numArgs, argTypes, proc, clientData\fR)
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.SH ARGUMENTS
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.AS Tcl_ValueType clientData
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.AP Tcl_Interp *interp in
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Interpreter in which new function will be defined.
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.AP char *name in
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Name for new function.
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.AP int numArgs in
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Number of arguments to new function; also gives size of \fIargTypes\fR array.
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.AP Tcl_ValueType *argTypes in
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Points to an array giving the permissible types for each argument to
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function.
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.AP Tcl_MathProc *proc in
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Procedure that implements the function.
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.AP ClientData clientData in
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Arbitrary one-word value to pass to \fIproc\fR when it is invoked.
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.BE
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.SH DESCRIPTION
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.PP
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Tcl allows a number of mathematical functions to be used in
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expressions, such as \fBsin\fR, \fBcos\fR, and \fBhypot\fR.
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\fBTcl_CreateMathFunc\fR allows applications to add additional functions
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to those already provided by Tcl or to replace existing functions.
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\fIName\fR is the name of the function as it will appear in expressions.
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If \fIname\fR doesn't already exist as a function then a new function
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is created. If it does exist, then the existing function is replaced.
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\fINumArgs\fR and \fIargTypes\fR describe the arguments to the function.
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Each entry in the \fIargTypes\fR array must be either TCL_INT, TCL_DOUBLE,
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or TCL_EITHER to indicate whether the corresponding argument must be an
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integer, a double-precision floating value, or either, respectively.
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.PP
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Whenever the function is invoked in an expression Tcl will invoke
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\fIproc\fR. \fIProc\fR should have arguments and result that match
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the type \fBTcl_MathProc\fR:
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.CS
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typedef int Tcl_MathProc(
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ClientData \fIclientData\fR,
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Tcl_Interp *\fIinterp\fR,
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Tcl_Value *\fIargs\fR,
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Tcl_Value *\fIresultPtr\fR);
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.CE
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.PP
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When \fIproc\fR is invoked the \fIclientData\fR and \fIinterp\fR
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arguments will be the same as those passed to \fBTcl_CreateMathFunc\fR.
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\fIArgs\fR will point to an array of \fInumArgs\fR Tcl_Value structures,
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which describe the actual arguments to the function:
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.CS
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typedef struct Tcl_Value {
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Tcl_ValueType \fItype\fR;
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.VS
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.VE
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long \fIintValue\fR;
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double \fIdoubleValue\fR;
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} Tcl_Value;
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.CE
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.PP
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The \fItype\fR field indicates the type of the argument and is
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either TCL_INT or TCL_DOUBLE.
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It will match the \fIargTypes\fR value specified for the function unless
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the \fIargTypes\fR value was TCL_EITHER. Tcl converts
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the argument supplied in the expression to the type requested in
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\fIargTypes\fR, if that is necessary.
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Depending on the value of the \fItype\fR field, the \fIintValue\fR
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or \fIdoubleValue\fR field will contain the actual value of the argument.
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.PP
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\fIProc\fR should compute its result and store it either as an integer
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in \fIresultPtr->intValue\fR or as a floating value in
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\fIresultPtr->doubleValue\fR.
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It should set also \fIresultPtr->type\fR to either TCL_INT or TCL_DOUBLE
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to indicate which value was set.
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Under normal circumstances \fIproc\fR should return TCL_OK.
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If an error occurs while executing the function, \fIproc\fR should
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return TCL_ERROR and leave an error message in \fIinterp->result\fR.
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.SH KEYWORDS
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expression, mathematical function
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