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  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 permis­
                                              sible   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

       Tcl  allows  a number of mathematical functions to be used
       in expressions, such as sin,  cos,  and  hypot.   Tcl_Cre­
       ateMathFunc  allows  applications  to add additional func­
       tions 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 func­
       tion.  Each entry in the argTypes  array  must  be  either
       TCL_INT, TCL_DOUBLE, or TCL_EITHER to indicate whether the

       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 struc­
       tures, which describe the actual arguments  to  the  func­
       tion:
              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 indi­
       cate 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