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nan.3p (2786B)

    

  1. '\" et
  2. .TH NAN "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. nan,
  12. nanf,
  13. nanl
  14. \(em return quiet NaN
  15. .SH SYNOPSIS
  16. .LP
  17. .nf
  18. #include <math.h>
  19. .P
  20. double nan(const char *\fItagp\fP);
  21. float nanf(const char *\fItagp\fP);
  22. long double nanl(const char *\fItagp\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. The function call \fInan\fR("\fIn-char-sequence\fR") shall be
  30. equivalent to:
  31. .sp
  32. .RS 4
  33. .nf
  35. strtod("NAN(\fIn-char-sequence\fP)", (char **) NULL);
  36. .fi
  37. .P
  38. .RE
  39. .P
  40. The function call \fInan\fR("\|") shall be equivalent to:
  41. .sp
  42. .RS 4
  43. .nf
  45. strtod("NAN()", (char **) NULL)
  46. .fi
  47. .P
  48. .RE
  49. .P
  50. If
  51. .IR tagp
  52. does not point to an
  53. .IR n -\c
  54. .BR char
  55. sequence or an empty string, the function call shall be equivalent to:
  56. .sp
  57. .RS 4
  58. .nf
  60. strtod("NAN", (char **) NULL)
  61. .fi
  62. .P
  63. .RE
  64. .P
  65. Function calls to
  66. \fInanf\fR()
  67. and
  68. \fInanl\fR()
  69. are equivalent to the corresponding function calls to
  70. \fIstrtof\fR()
  71. and
  72. \fIstrtold\fR().
  73. .SH "RETURN VALUE"
  74. These functions shall return a quiet NaN, if available, with content
  75. indicated through
  76. .IR tagp .
  77. .P
  78. If the implementation does not support quiet NaNs, these functions
  79. shall return zero.
  80. .SH ERRORS
  81. No errors are defined.
  82. .LP
  83. .IR "The following sections are informative."
  84. .SH EXAMPLES
  85. None.
  86. .SH "APPLICATION USAGE"
  87. None.
  88. .SH RATIONALE
  89. None.
  90. .SH "FUTURE DIRECTIONS"
  91. None.
  92. .SH "SEE ALSO"
  93. .IR "\fIstrtod\fR\^(\|)"
  94. .P
  95. The Base Definitions volume of POSIX.1\(hy2017,
  96. .IR "\fB<math.h>\fP"
  97. .\"
  98. .SH COPYRIGHT
  99. Portions of this text are reprinted and reproduced in electronic form
  100. from IEEE Std 1003.1-2017, Standard for Information Technology
  101. -- Portable Operating System Interface (POSIX), The Open Group Base
  102. Specifications Issue 7, 2018 Edition,
  103. Copyright (C) 2018 by the Institute of
  104. Electrical and Electronics Engineers, Inc and The Open Group.
  105. In the event of any discrepancy between this version and the original IEEE and
  106. The Open Group Standard, the original IEEE and The Open Group Standard
  107. is the referee document. The original Standard can be obtained online at
  108. http://www.opengroup.org/unix/online.html .
  109. .PP
  110. Any typographical or formatting errors that appear
  111. in this page are most likely
  112. to have been introduced during the conversion of the source files to
  113. man page format. To report such errors, see
  114. https://www.kernel.org/doc/man-pages/reporting_bugs.html .