WSTestHeadWithArgCount (C Function)
int WSTestHeadWithArgCount(WSLINK l, const char *s, int *n)
tests that the next object to be read from the WSTP connection specified by l is an expression with head s, and that the number of arguments of the expression is n.
Details
- WSTestHeadWithArgCount() fails if the current expression on the link is not a function with a symbol as a head, if the name of the symbol does not match s, or if the number of arguments for the function is not n.
- WSTestHeadWithArgCount() stores the actual number of arguments to the function in n when the function returns.
- WSTestHeadWithArgCount() returns 0 in the event of an error, and a nonzero value if the function succeeds.
- Use WSError() to retrieve the error code if WSTestHeadWithArgCount() fails.
- WSTestHeadWithArgCount() will reset the stream pointer to the expression on the link just prior to calling WSTestHeadWithArgCount() if the function fails. This operation behaves as if the programmer called WSCreateMark(l); WSTestHeadWithArgCount(...); WSSeekToMark(...).
- WSTestHeadWithArgCount() is declared in the WSTP header file wstp.h.
Examples
Basic Examples (1)
#include "wstp.h"
/* A function to test whether the next expression on the Link is Plus[a,b] */
void f(WSLINK l)
{
int args = 2;
const char *symbol;
if(! WSTestHeadWithArgCount(l, "Plus", &args))
{ /* Next expression is not Plus, or does not have two args */ }
if(! WSGetSymbol(l, &symbol))
{ /* Unable to read symbol */ }
/* Check if symbol is 'a' */
WSReleaseSymbol(l, symbol);
if(! WSGetSymbol(l, &symbol))
{ /* Unable to read symbol */ }
/* Check if the symbol is 'b' */
WSReleaseSymbol(l, symbol);
}