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atanh.3p (4773B)

    

  1. '\" et
  2. .TH ATANH "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. atanh,
  12. atanhf,
  13. atanhl
  14. \(em inverse hyperbolic tangent functions
  15. .SH SYNOPSIS
  16. .LP
  17. .nf
  18. #include <math.h>
  19. .P
  20. double atanh(double \fIx\fP);
  21. float atanhf(float \fIx\fP);
  22. long double atanhl(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 inverse hyperbolic tangent of their
  30. 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 inverse
  43. hyperbolic tangent of their argument.
  44. .P
  45. If
  46. .IR x
  47. is \(+-1, a pole error shall occur, and
  48. \fIatanh\fR(),
  49. \fIatanhf\fR(),
  50. and
  51. \fIatanhl\fR()
  52. shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL,
  53. respectively, with the same sign as the correct value of the function.
  54. .P
  55. For finite |\fIx\fR|>1, a domain error shall occur, and
  56. either a NaN (if supported), or
  57. an implementation-defined value shall be returned.
  58. .P
  59. If
  60. .IR x
  61. is NaN, a NaN shall be returned.
  62. .P
  63. If
  64. .IR x
  65. is \(+-0,
  66. .IR x
  67. shall be returned.
  68. .P
  69. If
  70. .IR x
  71. is \(+-Inf, a domain error shall occur, and a NaN shall be returned.
  72. .P
  73. If
  74. .IR x
  75. is subnormal, a range error may occur
  76. .br
  77. and
  78. .IR x
  79. should be returned.
  80. .P
  81. If
  82. .IR x
  83. is not returned,
  84. \fIatanh\fR(),
  85. \fIatanhf\fR(),
  86. and
  87. \fIatanhl\fR()
  88. shall return an implementation-defined value no greater in magnitude
  89. than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.
  90. .SH ERRORS
  91. These functions shall fail if:
  92. .IP "Domain\ Error" 12
  93. The
  94. .IR x
  95. argument is finite and not in the range [\-1,1],
  96. or is \(+-Inf.
  97. .RS 12 
  98. .P
  99. If the integer expression (\fImath_errhandling\fR & MATH_ERRNO) is
  100. non-zero, then
  101. .IR errno
  102. shall be set to
  103. .BR [EDOM] .
  104. If the integer expression (\fImath_errhandling\fR & MATH_ERREXCEPT) is
  105. non-zero, then the invalid floating-point exception shall be raised.
  106. .RE
  107. .IP "Pole\ Error" 12
  108. The
  109. .IR x
  110. argument is \(+-1.
  111. .RS 12 
  112. .P
  113. If the integer expression (\fImath_errhandling\fR & MATH_ERRNO) is
  114. non-zero, then
  115. .IR errno
  116. shall be set to
  117. .BR [ERANGE] .
  118. If the integer expression (\fImath_errhandling\fR & MATH_ERREXCEPT) is
  119. non-zero, then the divide-by-zero floating-point exception shall be
  120. raised.
  121. .RE
  122. .br
  123. .P
  124. These functions may fail if:
  125. .IP "Range\ Error" 12
  126. The value of
  127. .IR x
  128. is subnormal.
  129. .RS 12 
  130. .P
  131. If the integer expression (\fImath_errhandling\fR & MATH_ERRNO) is
  132. non-zero, then
  133. .IR errno
  134. shall be set to
  135. .BR [ERANGE] .
  136. If the integer expression (\fImath_errhandling\fR & MATH_ERREXCEPT) is
  137. non-zero, then the underflow floating-point exception shall be raised.
  138. .RE
  139. .LP
  140. .IR "The following sections are informative."
  141. .SH EXAMPLES
  142. None.
  143. .SH "APPLICATION USAGE"
  144. On error, the expressions (\fImath_errhandling\fR & MATH_ERRNO) and
  145. (\fImath_errhandling\fR & MATH_ERREXCEPT) are independent of each
  146. other, but at least one of them must be non-zero.
  147. .SH RATIONALE
  148. None.
  149. .SH "FUTURE DIRECTIONS"
  150. None.
  151. .SH "SEE ALSO"
  152. .IR "\fIfeclearexcept\fR\^(\|)",
  153. .IR "\fIfetestexcept\fR\^(\|)",
  154. .IR "\fItanh\fR\^(\|)"
  155. .P
  156. The Base Definitions volume of POSIX.1\(hy2017,
  157. .IR "Section 4.20" ", " "Treatment of Error Conditions for Mathematical Functions",
  158. .IR "\fB<math.h>\fP"
  159. .\"
  160. .SH COPYRIGHT
  161. Portions of this text are reprinted and reproduced in electronic form
  162. from IEEE Std 1003.1-2017, Standard for Information Technology
  163. -- Portable Operating System Interface (POSIX), The Open Group Base
  164. Specifications Issue 7, 2018 Edition,
  165. Copyright (C) 2018 by the Institute of
  166. Electrical and Electronics Engineers, Inc and The Open Group.
  167. In the event of any discrepancy between this version and the original IEEE and
  168. The Open Group Standard, the original IEEE and The Open Group Standard
  169. is the referee document. The original Standard can be obtained online at
  170. http://www.opengroup.org/unix/online.html .
  171. .PP
  172. Any typographical or formatting errors that appear
  173. in this page are most likely
  174. to have been introduced during the conversion of the source files to
  175. man page format. To report such errors, see
  176. https://www.kernel.org/doc/man-pages/reporting_bugs.html .