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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 4921 | Serge | 1 | /* |
| 2 | * compute 10**x by successive squaring. |
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| 3 | */ |
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| 4 | |||
| 5 | #include <_ansi.h> |
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| 6 | #include "std.h" |
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| 7 | |||
| 8 | double |
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| 9 | _DEFUN (__exp10, (x), |
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| 10 | unsigned x) |
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| 11 | { |
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| 12 | static _CONST double powtab[] = |
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| 13 | {1.0, |
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| 14 | 10.0, |
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| 15 | 100.0, |
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| 16 | 1000.0, |
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| 17 | 10000.0}; |
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| 18 | |||
| 19 | if (x < (sizeof (powtab) / sizeof (double))) |
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| 20 | return powtab[x]; |
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| 21 | else if (x & 1) |
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| 22 | { |
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| 23 | return 10.0 * __exp10 (x - 1); |
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| 24 | } |
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| 25 | else |
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| 26 | { |
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| 27 | double n = __exp10 (x / 2); |
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| 28 | return n * n; |
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| 29 | } |
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| 30 | } |