Last change
on this file since 567 was
444,
checked in by satin@…, 6 years ago
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add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc
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File size:
1.3 KB
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1 | |
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2 | /* @(#)z_atan.c 1.0 98/08/13 */ |
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3 | |
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4 | /* |
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5 | FUNCTION |
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6 | <<atan>>, <<atanf>>---arc tangent |
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7 | |
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8 | INDEX |
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9 | atan |
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10 | INDEX |
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11 | atanf |
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12 | |
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13 | SYNOPSIS |
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14 | #include <math.h> |
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15 | double atan(double <[x]>); |
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16 | float atanf(float <[x]>); |
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17 | |
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18 | DESCRIPTION |
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19 | |
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20 | <<atan>> computes the inverse tangent (arc tangent) of the input value. |
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21 | |
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22 | <<atanf>> is identical to <<atan>>, save that it operates on <<floats>>. |
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23 | |
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24 | RETURNS |
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25 | @ifnottex |
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26 | <<atan>> returns a value in radians, in the range of -pi/2 to pi/2. |
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27 | @end ifnottex |
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28 | @tex |
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29 | <<atan>> returns a value in radians, in the range of $-\pi/2$ to $\pi/2$. |
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30 | @end tex |
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31 | |
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32 | PORTABILITY |
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33 | <<atan>> is ANSI C. <<atanf>> is an extension. |
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34 | |
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35 | */ |
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36 | |
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37 | /****************************************************************** |
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38 | * Arctangent |
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39 | * |
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40 | * Input: |
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41 | * x - floating point value |
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42 | * |
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43 | * Output: |
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44 | * arctan of x |
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45 | * |
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46 | * Description: |
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47 | * This routine returns the arctan of x. |
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48 | * |
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49 | *****************************************************************/ |
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50 | |
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51 | #include "fdlibm.h" |
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52 | #include "zmath.h" |
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53 | |
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54 | #ifndef _DOUBLE_IS_32BITS |
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55 | |
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56 | double |
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57 | atan (double x) |
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58 | { |
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59 | switch (numtest (x)) |
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60 | { |
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61 | case NAN: |
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62 | errno = EDOM; |
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63 | return (x); |
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64 | case INF: |
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65 | /* this should check to see if neg NaN or pos NaN... */ |
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66 | return (__PI_OVER_TWO); |
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67 | case 0: |
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68 | return (0.0); |
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69 | default: |
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70 | return (atangent (x, 0, 0, 0)); |
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71 | } |
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72 | } |
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73 | |
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74 | #endif /* _DOUBLE_IS_32BITS */ |
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