Vocabulary
alien.syntax

Syntax

FUNCTION: return name ( parameters ) ;

Inputs and outputs

return	a C return type
name	a C function name
parameters	a comma-separated sequence of type/name pairs; type1 arg1, type2 arg2, ...

Word description
Defines a new word name which calls the C library function with the same name in the logical library given by the most recent LIBRARY: declaration.

The new word must be compiled before being executed.

Examples
For example, suppose the foo library exports the following function:

void the_answer(char* question, int value) { printf("The answer to %s is %d. ",question,value); }

You can define a word for invoking it:

LIBRARY: foo FUNCTION: void the_answer ( c-string question, int value ) ; "the question" 42 the_answer
The answer to the question is 42.

Using the c-string type instead of char* causes the FFI to automatically convert Factor strings to C strings. See C strings for more information on using strings with the FFI.

Notes
Note that the parentheses and commas are only syntax sugar and can be omitted; they serve no purpose other than to make the declaration easier to read. The following definitions are equivalent:

FUNCTION: void glHint ( GLenum target, GLenum mode ) ; FUNCTION: void glHint GLenum target GLenum mode ;

To make a Factor word with a name different from the C function, use FUNCTION-ALIAS:.

See also
FUNCTION-ALIAS:

Definition

USING: alien.parser words ;

IN: alien.syntax

SYNTAX: FUNCTION: (FUNCTION:) make-function define-inline ;