65 lines
1.9 KiB
C
65 lines
1.9 KiB
C
/*
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FUNCTION
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<<atof>>, <<atoff>>---string to double or float
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INDEX
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atof
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INDEX
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atoff
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SYNOPSIS
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#include <stdlib.h>
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double atof(const char *<[s]>);
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float atoff(const char *<[s]>);
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DESCRIPTION
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<<atof>> converts the initial portion of a string to a <<double>>.
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<<atoff>> converts the initial portion of a string to a <<float>>.
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The functions parse the character string <[s]>,
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locating a substring which can be converted to a floating-point
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value. The substring must match the format:
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. [+|-]<[digits]>[.][<[digits]>][(e|E)[+|-]<[digits]>]
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The substring converted is the longest initial
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fragment of <[s]> that has the expected format, beginning with
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the first non-whitespace character. The substring
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is empty if <<str>> is empty, consists entirely
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of whitespace, or if the first non-whitespace character is
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something other than <<+>>, <<->>, <<.>>, or a digit.
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<<atof(<[s]>)>> is implemented as <<strtod(<[s]>, NULL)>>.
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<<atoff(<[s]>)>> is implemented as <<strtof(<[s]>, NULL)>>.
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RETURNS
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<<atof>> returns the converted substring value, if any, as a
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<<double>>; or <<0.0>>, if no conversion could be performed.
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If the correct value is out of the range of representable values, plus
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or minus <<HUGE_VAL>> is returned, and <<ERANGE>> is stored in
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<<errno>>.
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If the correct value would cause underflow, <<0.0>> is returned
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and <<ERANGE>> is stored in <<errno>>.
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<<atoff>> obeys the same rules as <<atof>>, except that it
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returns a <<float>>.
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PORTABILITY
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<<atof>> is ANSI C. <<atof>>, <<atoi>>, and <<atol>> are subsumed by <<strod>>
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and <<strol>>, but are used extensively in existing code. These functions are
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less reliable, but may be faster if the argument is verified to be in a valid
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range.
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Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
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<<lseek>>, <<read>>, <<sbrk>>, <<write>>.
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*/
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#include <stdlib.h>
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#include <_ansi.h>
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double
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_DEFUN (atof, (s),
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_CONST char *s)
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{
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return strtod (s, NULL);
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}
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