Tcl_CreateMathFunc(3Tcl)			      Tcl_CreateMathFunc(3Tcl)

NAME    [Toc]    [Back]

     Tcl_CreateMathFunc	- Define a new math function for expressions

SYNOPSIS    [Toc]    [Back]

     #include <tcl.h>

     Tcl_CreateMathFunc(interp,	name, numArgs, argTypes, proc, clientData)

ARGUMENTS    [Toc]    [Back]

     Tcl_Interp	     *interp	  (in)	    Interpreter	in which new function
					    will be defined.

     char	     *name	  (in)	    Name for new function.

     int	     numArgs	  (in)	    Number of arguments	to new
					    function;  also gives size of
					    argTypes array.

     Tcl_ValueType   *argTypes	  (in)	    Points to an array giving the
					    permissible	types for each
					    argument to	function.

     Tcl_MathProc    *proc	  (in)	    Procedure that implements the
					    function.

     ClientData	     clientData	  (in)	    Arbitrary one-word value to	pass
					    to proc when it is invoked.

DESCRIPTION    [Toc]    [Back]

     Tcl allows	a number of mathematical functions to be used in expressions,
     such as sin, cos, and hypot.  Tcl_CreateMathFunc allows applications to
     add additional functions to those already provided	by Tcl or to replace
     existing functions.  Name is the name of the function as it will appear
     in	expressions.  If name doesn't already exist as a function then a new
     function is created.  If it does exist, then the existing function	is
     replaced.	NumArgs	and argTypes describe the arguments to the function.
     Each entry	in the argTypes	array must be either TCL_INT, TCL_DOUBLE, or
     TCL_EITHER	to indicate whether the	corresponding argument must be an
     integer, a	double-precision floating value, or either, respectively.

     Whenever the function is invoked in an expression Tcl will	invoke proc.
     Proc should have arguments	and result that	match the type Tcl_MathProc:
	  typedef int Tcl_MathProc(
	       ClientData clientData,
	       Tcl_Interp *interp,
	       Tcl_Value *args,
	       Tcl_Value *resultPtr);

     When proc is invoked the clientData and interp arguments will be the same
     as	those passed to	Tcl_CreateMathFunc.  Args will point to	an array of
     numArgs Tcl_Value structures, which describe the actual arguments to the



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Tcl_CreateMathFunc(3Tcl)			      Tcl_CreateMathFunc(3Tcl)



     function:
	  typedef struct Tcl_Value {
	       Tcl_ValueType type;
	       long intValue;						      |
	       double doubleValue;
	  } Tcl_Value;

     The type field indicates the type of the argument and is either TCL_INT
     or	TCL_DOUBLE.  It	will match the argTypes	value specified	for the
     function unless the argTypes value	was TCL_EITHER.	Tcl converts the
     argument supplied in the expression to the	type requested in argTypes, if
     that is necessary.	 Depending on the value	of the type field, the
     intValue or doubleValue field will	contain	the actual value of the
     argument.

     Proc should compute its result and	store it either	as an integer in
     resultPtr->intValue or as a floating value	in resultPtr->doubleValue.  It
     should set	also resultPtr->type to	either TCL_INT or TCL_DOUBLE to
     indicate which value was set.  Under normal circumstances proc should
     return TCL_OK.  If	an error occurs	while executing	the function, proc
     should return TCL_ERROR and leave an error	message	in interp->result.

KEYWORDS    [Toc]    [Back]

     expression, mathematical function


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