dollar
Note: This is taken from the Chicken Wiki, where a more recent version could be available.
A convenience macro for direct calls to foreign functions.
Note: this extension is only needed for CHICKEN versions 2.425 and higher
[syntax] ($ [RETURNTYPE] NAME (TYPE ARGUMENT) ...)
Invokes a C/C++ function by evaluating the arguments, performing the neccessary type-conversions for the foreign type-specifiers and calling NAME (which must be a symbol). If a return-type is given, then the result will be converted properly and returned. Callbacks into Scheme are not allowed inside the invoked foreign code. The type/argument lists may also be literal Scheme data or expressions of the form (quote LITERAL) or (location ...) - in this case the arguments are converted according to the type of the literal or are treated as a c-pointer, respectively. Booleans, characters, numbers, strings, SRFI-4 number vectors and symbols are converted, all other data is passed as being of type scheme-object.
($ printf "%d times Hello, %s!\n" 1000 "world")
(define f 99.2)
(let-location ((double n))
(let ((f ($ double modf (double f) (location n))))
(cons n f) ) )If no return type is given, void is assumed. This macro expands into one of the foreign-lambda*, foreign-code or foreign-value forms.
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