Path: utzoo!utgpu!water!watmath!clyde!rutgers!sri-unix!quintus!sun!decwrl!labrea!aurora!amelia!ames!sdcsvax!sdcc6!ix426
From: ix426@sdcc6.ucsd.EDU (tom stockfish)
Newsgroups: comp.lang.c
Subject: Re: Allocating two dimensional arrays
Message-ID: <3590@sdcc6.ucsd.EDU>
Date: 21 Jan 88 23:13:56 GMT
References: <419@nikhefh.hep.nl> <10278@mimsy.UUCP>
Reply-To: ix426@sdcc6.ucsd.edu.UUCP (tom stockfish)
Organization: University of California, San Diego
Lines: 28

In article <10278@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
X 
X [code defining create_matrix() which returns "data_t **", a "matrix" of
X  the sort that "argv" is, and free_matrix() ]
X 
X Exercises:
X 1.  How *does* it work?
X 2.  Modify it to create a four-dimensional matrix of size W by X by
X     Y by Z.
X 3.  Modify it to produce upper or lower triangular matrices, without
X     using any more calls to malloc, and without wasting space (no
X     `mem' elements left over).


4.  Modify it so that it uses only *one* malloc() call, the pointer
    it returns can be handed *directly* to free() (no "free_matrix()"
    routine needed), and a "true" matrix (or rather, pointer to
    the first element of it) can be easily obtained so it can be
    sent to a fortran routine (assuming the fortran routine can
    operate on the transpose).  Oh yes, it must be portable, too.
    (Solution to follow at later date).


5.  Prove that #4 cannot be done portably if the type of the matrix
    is not specified at compile time.
-- 

||  Tom Stockfisch, UCSD Chemistry   tps@chem.ucsd.edu