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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30 | * The function p1evl() assumes that coef[N] = 1.0 and is |
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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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51 | |
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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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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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63 | |
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64 | return ans; |
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65 | } |
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66 | |
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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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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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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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84 | return ans; |
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85 | } |
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