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Annotation of 3BSD/cmd/lisp/subbig.c, revision 1.1

1.1     ! root        1: #include "global.h"
        !             2: 
        !             3: lispval
        !             4: subbig(pos,neg)
        !             5: lispval pos, neg;
        !             6: {
        !             7:        register lispval work;
        !             8:        int *sp(); lispval adbig();
        !             9:        register int *mysp = sp() - 2;
        !            10:        register int *ersatz = mysp;
        !            11: 
        !            12:        for(work = neg; work!=0; work = work->CDR) {
        !            13:                stack(-work->i, (mysp -= 2));
        !            14:        }
        !            15:        mysp[3] = 0;
        !            16:        return(adbig(pos,ersatz));
        !            17: }
        !            18: /*
        !            19:  * subbig -- subtract one bignum from another.
        !            20:  *
        !            21:  * What this does is it negates each coefficient of a copy of the bignum
        !            22:  * which is just pushed on the stack for convenience.  This may give rise
        !            23:  * to a bignum which is not in canonical form, but is nonetheless a repre
        !            24:  * sentation of a bignum.  Addbig then adds it to a bignum, and produces
        !            25:  * a result in canonical form.
        !            26:  */

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