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atan.3p (3659B)

    

  1. '\" et
  2. .TH ATAN "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
  3. .\"
  4. .SH PROLOG
  5. This manual page is part of the POSIX Programmer's Manual.
  6. The Linux implementation of this interface may differ (consult
  7. the corresponding Linux manual page for details of Linux behavior),
  8. or the interface may not be implemented on Linux.
  9. .\"
  10. .SH NAME
  11. atan,
  12. atanf,
  13. atanl
  14. \(em arc tangent function
  15. .SH SYNOPSIS
  16. .LP
  17. .nf
  18. #include <math.h>
  19. .P
  20. double atan(double \fIx\fP);
  21. float atanf(float \fIx\fP);
  22. long double atanl(long double \fIx\fP);
  23. .fi
  24. .SH DESCRIPTION
  25. The functionality described on this reference page is aligned with the
  26. ISO\ C standard. Any conflict between the requirements described here and the
  27. ISO\ C standard is unintentional. This volume of POSIX.1\(hy2017 defers to the ISO\ C standard.
  28. .P
  29. These functions shall compute the principal value of the arc tangent of
  30. their argument
  31. .IR x .
  32. .P
  33. An application wishing to check for error situations should set
  34. .IR errno
  35. to zero and call
  36. .IR feclearexcept (FE_ALL_EXCEPT)
  37. before calling these functions. On return, if
  38. .IR errno
  39. is non-zero or \fIfetestexcept\fR(FE_INVALID | FE_DIVBYZERO |
  40. FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.
  41. .SH "RETURN VALUE"
  42. Upon successful completion, these functions shall return the arc
  43. tangent of
  44. .IR x
  45. in the range [\-\(*p/2,\(*p/2] radians.
  46. .P
  47. If
  48. .IR x
  49. is NaN, a NaN shall be returned.
  50. .P
  51. If
  52. .IR x
  53. is \(+-0,
  54. .IR x
  55. shall be returned.
  56. .P
  57. If
  58. .IR x
  59. is \(+-Inf, \(+-\(*p/2 shall be returned.
  60. .P
  61. If
  62. .IR x
  63. is subnormal, a range error may occur
  64. .br
  65. and
  66. .IR x
  67. should be returned.
  68. .P
  69. If
  70. .IR x
  71. is not returned,
  72. \fIatan\fR(),
  73. \fIatanf\fR(),
  74. and
  75. \fIatanl\fR()
  76. shall return an implementation-defined value no greater in magnitude
  77. than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.
  78. .SH ERRORS
  79. These functions may fail if:
  80. .IP "Range\ Error" 12
  81. The value of
  82. .IR x
  83. is subnormal.
  84. .RS 12 
  85. .P
  86. If the integer expression (\fImath_errhandling\fR & MATH_ERRNO) is
  87. non-zero, then
  88. .IR errno
  89. shall be set to
  90. .BR [ERANGE] .
  91. If the integer expression (\fImath_errhandling\fR & MATH_ERREXCEPT) is
  92. non-zero, then the underflow floating-point exception shall be raised.
  93. .RE
  94. .LP
  95. .IR "The following sections are informative."
  96. .SH EXAMPLES
  97. None.
  98. .SH "APPLICATION USAGE"
  99. On error, the expressions (\fImath_errhandling\fR & MATH_ERRNO) and
  100. (\fImath_errhandling\fR & MATH_ERREXCEPT) are independent of each
  101. other, but at least one of them must be non-zero.
  102. .SH RATIONALE
  103. None.
  104. .SH "FUTURE DIRECTIONS"
  105. None.
  106. .SH "SEE ALSO"
  107. .IR "\fIatan2\fR\^(\|)",
  108. .IR "\fIfeclearexcept\fR\^(\|)",
  109. .IR "\fIfetestexcept\fR\^(\|)",
  110. .IR "\fIisnan\fR\^(\|)",
  111. .IR "\fItan\fR\^(\|)"
  112. .P
  113. The Base Definitions volume of POSIX.1\(hy2017,
  114. .IR "Section 4.20" ", " "Treatment of Error Conditions for Mathematical Functions",
  115. .IR "\fB<math.h>\fP"
  116. .\"
  117. .SH COPYRIGHT
  118. Portions of this text are reprinted and reproduced in electronic form
  119. from IEEE Std 1003.1-2017, Standard for Information Technology
  120. -- Portable Operating System Interface (POSIX), The Open Group Base
  121. Specifications Issue 7, 2018 Edition,
  122. Copyright (C) 2018 by the Institute of
  123. Electrical and Electronics Engineers, Inc and The Open Group.
  124. In the event of any discrepancy between this version and the original IEEE and
  125. The Open Group Standard, the original IEEE and The Open Group Standard
  126. is the referee document. The original Standard can be obtained online at
  127. http://www.opengroup.org/unix/online.html .
  128. .PP
  129. Any typographical or formatting errors that appear
  130. in this page are most likely
  131. to have been introduced during the conversion of the source files to
  132. man page format. To report such errors, see
  133. https://www.kernel.org/doc/man-pages/reporting_bugs.html .