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Annotation of 42BSD/ucb/lisp/franz/subbig.c, revision 1.1.1.1

1.1       root        1: #ifndef lint
                      2: static char *rcsid =
                      3:    "$Header: subbig.c,v 1.2 83/09/12 14:17:31 sklower Exp $";
                      4: #endif
                      5: 
                      6: /*                                     -[Sat Jan 29 13:36:05 1983 by jkf]-
                      7:  *     subbig.c                        $Locker:  $
                      8:  * bignum subtraction
                      9:  *
                     10:  * (c) copyright 1982, Regents of the University of California
                     11:  */
                     12: 
                     13: #include "global.h"
                     14: 
                     15: /*
                     16:  * subbig -- subtract one bignum from another.
                     17:  *
                     18:  * What this does is it negates each coefficient of a copy of the bignum
                     19:  * which is just pushed on the stack for convenience.  This may give rise
                     20:  * to a bignum which is not in canonical form, but is nonetheless a repre
                     21:  * sentation of a bignum.  Addbig then adds it to a bignum, and produces
                     22:  * a result in canonical form.
                     23:  */
                     24: lispval
                     25: subbig(pos,neg)
                     26: lispval pos, neg;
                     27: {
                     28:        register lispval work;
                     29:        lispval adbig();
                     30:        register long *mysp = sp() - 2;
                     31:        register long *ersatz = mysp;
                     32:        Keepxs();
                     33: 
                     34:        for(work = neg; work!=0; work = work->s.CDR) {
                     35:                stack((long)(mysp -= 2));
                     36:                stack(-work->i);
                     37:        }
                     38:        mysp[3] = 0;
                     39:        work = (adbig(pos,(lispval)ersatz));
                     40:        Freexs();
                     41:        return(work);
                     42: }

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