Tcl_CreateMathFunc(3)       Tcl Library Procedures       Tcl_CreateMathFunc(3)


       Tcl_CreateMathFunc - Define a new math function for expressions

       #include <tcl.h>

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

       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

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

       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

       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.

       expression, mathematical function

Tcl                                   7.0                Tcl_CreateMathFunc(3)