Tcl_CreateMathFunc(3)

NAME
Tcl_CreateMathFunc, Tcl_GetMathFuncInfo, Tcl_ListMathFuncs - Define, query and enumerate math functions for expressions

SYNOPSIS
#include <tcl.h>

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

int
Tcl_GetMathFuncInfo(interp, name, numArgsPtr, argTypesPtr, procPtr, clientDataPtr)

Tcl_Obj *
Tcl_ListMathFuncs(interp, pattern)

ARGUMENTS
Interpreter in which new function will be defined. Name for new function. Number of arguments to new function; also gives size of argTypes array. Points to an array giving the permissible types for each argument to function. Procedure that implements the function. Arbitrary one-word value to pass to proc when it is invoked. Points to a variable that will be set to contain the number of arguments to the function. Points to a variable that will be set to contain a pointer to an array giving the permissible types for each argument to the function which will need to be freed up using Tcl_Free. Points to a variable that will be set to contain a pointer to the implementation code for the function (or NULL if the function is implemented directly in bytecode.) Points to a variable that will be set to contain the clientData argument passed to Tcl_CreateMathFunc when the function was created if the function is not implemented directly in bytecode. Pattern to match against function names so as to filter them (by passing to Tcl_StringMatch), or NULL to not apply any filter.

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.

Tcl_GetMathFuncInfo retrieves the values associated with function name that were passed to a preceding Tcl_CreateMathFunc call. Normally, the return code is TCL_OK but if the named function does not exist, TCL_ERROR is returned and an error message is placed in the interpreter's result.

If an error did not occur, the array reference placed in the variable pointed to by argTypesPtr is newly allocated, and should be released by passing it to Tcl_Free. Some functions (the standard set implemented in the core) are implemented directly at the bytecode level; attempting to retrieve values for them causes a NULL to be stored in the variable pointed to by procPtr and the variable pointed to by clientDataPtr will not be modified.

Tcl_ListMathFuncs returns a Tcl object containing a list of all the math functions defined in the interpreter whose name matches pattern. In the case of an error, NULL is returned and an error message is left in the interpreter result, and otherwise the returned object will have a reference count of zero.

KEYWORDS
expression, mathematical function

SEE ALSO
expr(n), info(n), Tcl_Free(3), Tcl_NewListObj(3)