[3936ad3] | 1 | /* polevl.c |
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| 2 | * p1evl.c |
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| 3 | * |
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| 4 | * Evaluate polynomial |
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| 5 | * |
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| 6 | * |
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| 7 | * |
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| 8 | * SYNOPSIS: |
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| 9 | * |
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| 10 | * int N; |
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| 11 | * double x, y, coef[N+1], polevl[]; |
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| 12 | * |
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| 13 | * y = polevl( x, coef, N ); |
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| 14 | * |
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| 15 | * |
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| 16 | * |
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| 17 | * DESCRIPTION: |
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| 18 | * |
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| 19 | * Evaluates polynomial of degree N: |
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| 20 | * |
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| 21 | * 2 N |
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| 22 | * y = C + C x + C x +...+ C x |
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| 23 | * 0 1 2 N |
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| 24 | * |
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| 25 | * Coefficients are stored in reverse order: |
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| 26 | * |
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| 27 | * coef[0] = C , ..., coef[N] = C . |
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| 28 | * N 0 |
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| 29 | * |
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[447e9aa] | 30 | * The function p1evl() assumes that C_N = 1.0 and is |
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[3936ad3] | 31 | * omitted from the array. Its calling arguments are |
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| 32 | * otherwise the same as polevl(). |
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| 33 | * |
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| 34 | * |
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| 35 | * SPEED: |
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| 36 | * |
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| 37 | * In the interest of speed, there are no checks for out |
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| 38 | * of bounds arithmetic. This routine is used by most of |
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| 39 | * the functions in the library. Depending on available |
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| 40 | * equipment features, the user may wish to rewrite the |
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| 41 | * program in microcode or assembly language. |
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| 42 | * |
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| 43 | */ |
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| 44 | |
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| 45 | |
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| 46 | /* |
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| 47 | Cephes Math Library Release 2.1: December, 1988 |
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| 48 | Copyright 1984, 1987, 1988 by Stephen L. Moshier |
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| 49 | Direct inquiries to 30 Frost Street, Cambridge, MA 02140 |
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| 50 | */ |
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[e2af2a9] | 51 | |
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[0278e3f] | 52 | double polevl( double x, constant double *coef, int N ); |
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| 53 | double polevl( double x, constant double *coef, int N ) |
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| 54 | { |
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[3936ad3] | 55 | |
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| 56 | int i = 0; |
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| 57 | double ans = coef[i]; |
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| 58 | |
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| 59 | while (i < N) { |
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| 60 | i++; |
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| 61 | ans = ans * x + coef[i]; |
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| 62 | } |
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[a5af4e1] | 63 | |
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[0278e3f] | 64 | return ans; |
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[a5af4e1] | 65 | } |
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| 66 | |
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[3936ad3] | 67 | /* p1evl() */ |
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| 68 | /* N |
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| 69 | * Evaluate polynomial when coefficient of x is 1.0. |
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| 70 | * Otherwise same as polevl. |
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| 71 | */ |
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| 72 | |
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[0278e3f] | 73 | double p1evl( double x, constant double *coef, int N ); |
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| 74 | double p1evl( double x, constant double *coef, int N ) |
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| 75 | { |
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[a5af4e1] | 76 | int i=0; |
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| 77 | double ans = x+coef[i]; |
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| 78 | |
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| 79 | while (i < N-1) { |
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| 80 | i++; |
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| 81 | ans = ans*x + coef[i]; |
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| 82 | } |
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| 83 | |
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[0278e3f] | 84 | return ans; |
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[fad5dc1] | 85 | } |
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