🚀 go-pugleaf

This should really be in comp.lang.c, shouldn't it?

tim@osiris.usi.utah.edu (Tim Burns 581-4439) writes:
: Does anyone out there have a routine which does dynamic memory allocation
: which forces allocation __exactly__ the same as array allocation?  Or,
: can anyone give me a tip on how I might begin constructing such a utility?

The syntactic equivalence of pointers and arrays is a major problem of C.

	/* array of L arrays of M doubles */
	double A[L][M];

gives a continguous block of memory, as does:

	/* pointer to array of M doubles */
	double (*A)[M];

	/* Allocate L arrays of M doubles */
	A = (double (*)[M])malloc(L * sizeof(*A));
	if (L != 0 && M != 0 && A == (double (*)[M])0) .... //error


/* cf. char s[10]; and char *s = malloc(sizeof(*s)); ... */

However, the array of pointers to arrays example you gave (from
Numeric Recipes in C?) has a lot to commend it.  One major advantage
is if the array is large there may not be enough contiguous memory to
allocate a two-dimensional array but it may be allocated in smaller
chunks of one-d arrays.

Of course, if you are calling library routines that require two-d
arrays there's not much you can do.
-- 
Andrew Phillips (andrew@teslab.lab.oz.au) Phone +61 (Aust) 2 (Sydney) 287 6551