| 1 | #include "f2c.h"
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| 2 |
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| 3 | #undef abs
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| 4 | #include "math.h"
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| 5 | extern double f__cabs (double, double);
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| 6 | void
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| 7 | z_log (doublecomplex * r, doublecomplex * z)
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| 8 | {
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| 9 | double s, s0, t, t2, u, v;
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| 10 | double zi = z->i, zr = z->r;
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| 11 |
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| 12 | r->i = atan2 (zi, zr);
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| 13 | #ifdef Pre20000310
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| 14 | r->r = log (f__cabs (zr, zi));
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| 15 | #else
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| 16 | if (zi < 0)
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| 17 | zi = -zi;
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| 18 | if (zr < 0)
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| 19 | zr = -zr;
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| 20 | if (zr < zi)
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| 21 | {
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| 22 | t = zi;
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| 23 | zi = zr;
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| 24 | zr = t;
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| 25 | }
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| 26 | t = zi / zr;
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| 27 | s = zr * sqrt (1 + t * t);
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| 28 | /* now s = f__cabs(zi,zr), and zr = |zr| >= |zi| = zi */
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| 29 | if ((t = s - 1) < 0)
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| 30 | t = -t;
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| 31 | if (t > .01)
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| 32 | r->r = log (s);
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| 33 | else
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| 34 | {
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| 35 |
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| 36 | #ifdef Comment
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| 37 |
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| 38 | log (1 + x) = x - x ^ 2 / 2 + x ^ 3 / 3 - x ^ 4 / 4 + -...
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| 39 | = x (1 - x / 2 + x ^ 2 / 3 - +...)
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