CrtMathFnc

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     NAME
          Tcl_CreateMathFunc  -  Define  a  new  math   function   for
          expressions

     SYNOPSIS
          #include <tcl.h>

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

     ARGUMENTS
          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.
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     DESCRIPTION
          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 function:
               typedef struct Tcl_Value {
                    Tcl_ValueType type;
                    int 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
          expression, mathematical function