26.1.6.3 C pointers

C pointers are defined by the <pointer-type>

<pointer-type> → (pointer <ident>)

<ident> is the name of a previously defined type. Let us suppose the pointer type declaration:

(type ptr (pointer ident) ...)

If ident is the name of a structure type, Bigloo automatically creates structure accessors (see section Struct and Union types). Otherwise, it creates the following functions:

• A creator:

  (make-ptr::ptr nb::long)
  

  This function allocates memory for nb elements of type ident and returns a ptr to this zone. The memory is filled with the C Null value.

• A type checker:

  (ptr?::bool obj::obj)
  

  This function returns #t the argument obj is of type ptr and #f otherwise.

• A null checker:

  (ptr-null?::bool ::ptr)
  

  This function returns #t if its argument is Null and #f otherwise.

• A null creator:

  (make-null-ptr::ptr*)
  

  This function creates a NULL value of type ptr*.

• An equality checker:

  (=ptr*?::bool ::ptr* ::ptr*)
  

  This function returns #t if its arguments are equal and #f otherwise.

• Accessors and mutators:

  (ptr-ref::ident ::ptr ::long)
  (ptr-set!::obj ::ptr ::long ::ident)
  

  These functions read and store field values.

Here is an example of a program using pointer types:

(module foo 
   (extern 
    (type double* (pointer double) "double *")))

(define (make-vect::double* x y z)
   (let ((vect (make-double* 3)))
      (double*-set! vect 0 x)
      (double*-set! vect 1 y)
      (double*-set! vect 2 z)
      vect))

(define (vect-norm vect::double*)
   (sqrt (+ (expt (double*-ref vect 0) 2)
	    (expt (double*-ref vect 1) 2)
	    (expt (double*-ref vect 2) 2))))

(print (vect-norm (make-vect 1.2 4.5 -4.5)))

This document was generated on October 23, 2011 using texi2html 5.0.