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Annotation of researchv10no/cmd/cfront/libC/complex/cos.c, revision 1.1.1.1

1.1       root        1: 
                      2: #include "complex.h"
                      3: #include "const.h"
                      4: 
                      5: complex cos(complex z)
                      6: /*
                      7:        The cosine of z: cos(z)=cosh(iz).
                      8: */
                      9: {
                     10:        complex y(-z.im, z.re); 
                     11:        return cosh(y);
                     12: }
                     13: 
                     14: 
                     15: 
                     16: complex cosh(complex z)
                     17: /*
                     18:        The complex hyperbolic cosine of z
                     19: */
                     20: {
                     21:        double  cosh_x, sinh_x, cos_y, sin_y;
                     22: 
                     23: #define        COSH_GOOD       1e7
                     24: #define        COSH_HUGE       1e38
                     25: 
                     26:        if (z.re > MAX_EXPONENT) {
                     27:                complex_error(C_COSH_RE, z.re);
                     28:                cosh_x = sinh_x = COSH_HUGE;
                     29:        }
                     30:        else if (z.re < MIN_EXPONENT) {
                     31:                complex_error(C_COSH_RE, z.re);
                     32:                cosh_x = COSH_HUGE;
                     33:                sinh_x = -COSH_HUGE;
                     34:        }
                     35:        else {
                     36:                double pos_exp = exp(z.re); 
                     37:                double neg_exp = 1/pos_exp;
                     38:                cosh_x = (pos_exp + neg_exp)/2;
                     39:                sinh_x = (pos_exp - neg_exp)/2;
                     40:        }
                     41: 
                     42:        if (ABS(z.im) > COSH_GOOD) {
                     43:                complex_error(C_COSH_IM, z.im);
                     44:                cos_y = sin_y = 0;
                     45:        }
                     46:        else {
                     47:                cos_y = cos(z.im);
                     48:                sin_y = sin(z.im);
                     49:        }
                     50: 
                     51:        return complex(cos_y*cosh_x, sin_y*sinh_x);
                     52: }

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