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       tfmtstrtod.3 (1285B)
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            1 .TH FMTSTRTOD 3
            2 .SH NAME
            3 fmtstrtod, fmtcharstod \ - convert text to numbers
            4 .SH SYNOPSIS
            5 .B #include <utf.h>
            6 .br
            7 .B #include <fmt.h>
            8 .PP
            9 .PP
           10 .B
           11 double        fmtstrtod(char *nptr, char **rptr)
           12 .PP
           13 .B
           14 double        fmtcharstod(int (*f)(void *), void *a)
           15 .SH DESCRIPTION
           16 .I Fmtstrtod
           17 converts a string pointed to by
           18 .I nptr
           19 to floating point representation and, if
           20 .I rptr
           21 is not zero, sets
           22 .I *rptr
           23 to point to the input character immediately after the string converted.
           24 .I Fmtstrtod
           25 recognizes an optional string of tabs and spaces,
           26 then an optional sign, then a string of digits optionally
           27 containing a decimal point, then an optional 
           28 .L e
           29 or
           30 .L E
           31 followed by an optionally signed integer.
           32 .PP
           33 .PP
           34 .I Fmtcharstod
           35 interprets floating point numbers in the manner of
           36 .IR atof ,
           37 but gets successive characters by calling
           38 .BR (*\fIf\fP)(a) .
           39 The last call to
           40 .I f
           41 terminates the scan, so it must have returned a character that
           42 is not a legal continuation of a number.
           43 Therefore, it may be necessary to back up the input stream one character
           44 after calling
           45 .IR fmtcharstod .
           46 .SH SOURCE
           47 .B https://9fans.github.io/plan9port/unix
           48 .SH SEE ALSO
           49 .IR fscanf (3)
           50 .SH DIAGNOSTICS
           51 Zero is returned if the beginning of the input string is not interpretable
           52 as a number; even in this case,
           53 .I rptr
           54 will be updated.