1FLOOR(P) POSIX Programmer's Manual FLOOR(P)
2
3
4
6 floor, floorf, floorl - floor function
7
9 #include <math.h>
10
11 double floor(double x);
12 float floorf(float x);
13 long double floorl(long double x);
14
15
17 These functions shall compute the largest integral value not greater
18 than x.
19
20 An application wishing to check for error situations should set errno
21 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
22 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID
23 | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
24 occurred.
25
27 Upon successful completion, these functions shall return the largest
28 integral value not greater than x, expressed as a double, float, or
29 long double, as appropriate for the return type of the function.
30
31 If x is NaN, a NaN shall be returned.
32
33 If x is ±0 or ±Inf, x shall be returned.
34
35 If the correct value would cause overflow, a range error shall occur
36 and floor(), floorf(), and floorl() shall return the value of the macro
37 -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.
38
40 These functions shall fail if:
41
42 Range Error
43 The result would cause an overflow.
44
45 If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
46 then errno shall be set to [ERANGE]. If the integer expression
47 (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow
48 floating-point exception shall be raised.
49
50
51 The following sections are informative.
52
54 None.
55
57 The integral value returned by these functions might not be expressible
58 as an int or long. The return value should be tested before assigning
59 it to an integer type to avoid the undefined results of an integer
60 overflow.
61
62 The floor() function can only overflow when the floating-point repre‐
63 sentation has DBL_MANT_DIG > DBL_MAX_EXP.
64
65 On error, the expressions (math_errhandling & MATH_ERRNO) and
66 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
67 at least one of them must be non-zero.
68
70 None.
71
73 None.
74
76 ceil() , feclearexcept() , fetestexcept() , isnan() , the Base Defini‐
77 tions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error
78 Conditions for Mathematical Functions, <math.h>
79
81 Portions of this text are reprinted and reproduced in electronic form
82 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
83 -- Portable Operating System Interface (POSIX), The Open Group Base
84 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
85 Electrical and Electronics Engineers, Inc and The Open Group. In the
86 event of any discrepancy between this version and the original IEEE and
87 The Open Group Standard, the original IEEE and The Open Group Standard
88 is the referee document. The original Standard can be obtained online
89 at http://www.opengroup.org/unix/online.html .
90
91
92
93IEEE/The Open Group 2003 FLOOR(P)