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Annotation of researchv10dc/libc/math/hypot.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * hypot -- sqrt(p*p+q*q), but overflows only if the result does.
        !             3:  * See Cleve Moler and Donald Morrison,
        !             4:  * ``Replacing Square Roots by Pythagorean Sums,''
        !             5:  * IBM Journal of Research and Development,
        !             6:  * Vol. 27, Number 6, pp. 577-581, Nov. 1983
        !             7:  */
        !             8: double hypot(p, q)
        !             9: double p, q;
        !            10: {
        !            11:        double r, s, pfac;
        !            12:        if(p<0) p = -p;
        !            13:        if(q<0) q = -q;
        !            14:        if(p<q){ r=p; p=q; q=r; }
        !            15:        if(p==0) return 0;
        !            16:        pfac = p;
        !            17:        r = q = q/p;
        !            18:        p = 1.0;
        !            19:        for(;;){
        !            20:                r*=r;
        !            21:                s=r+4;
        !            22:                if(s==4)
        !            23:                        return p*pfac;
        !            24:                r/=s;
        !            25:                p+=2*r*p;
        !            26:                q*=r;
        !            27:                r=q/p;
        !            28:        }
        !            29: }
        !            30: double cabs(z)
        !            31: struct{
        !            32:        double x, y;
        !            33: }z;
        !            34: {
        !            35:        return hypot(z.x, z.y);
        !            36: }

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