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NAME
     Tcl_CreateMathFunc - Define a new math function for  expres-
     sions

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  func-
                                            tion.

     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 permissi-
                                            ble  types  for  each
                                            argument to function.

     Tcl_MathProc    *proc        (in)      Procedure that imple-
                                            ments 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;
            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   the
     interpreter's result.


KEYWORDS
     expression, mathematical function

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