35 lines
1.4 KiB
Groff
35 lines
1.4 KiB
Groff
.TH FESETROUND 3 "December 18, 2009"
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.UC 4
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.SH NAME
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fesetround, fegetround \- floating point rounding mode control
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.SH SYNOPSIS
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.nf
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.ft B
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#include <fenv.h>
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int fegetround(void);
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int fesetround(int \fIround\fP);
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.fi
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.SH DESCRIPTION
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These functions control the floating point rounding mode. One can use
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fegetround to determine the rounding mode currently in effect and fesetround
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the change the rounding mode. Four rounding modes are recognized: FE_TONEAREST,
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FE_DOWNWARD, FE_UPWARD and FE_TOWARDZERO. When rounding a value \fIx\fP to an
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integer \fIn\fP, the following approaches can be taken: FE_TONEAREST selects
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the \fIn\fP for which abs(fIx\fP - \fIn\fP) is minimal, preferring an even
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\fIn\fP if there are two possibilities; FE_DOWNWARD selects the largest \fIn\fP
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for which \fIn\fP <= fIx\fP; FE_UPWARD selects the smallest \fIn\fP for which
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\fIn\fP >= fIx\fP; and FE_TOWARDZERO selects \fIn\fP with the largest
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abs(\fIn\fP) for which abs(\fIn\fP) <= abs(\fIx\fP).
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.SH "RETURN VALUE"
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fegetround returns the current rounding mode. fesetround returns 0 if it was
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succesful in adjusting the rounding mode and -1 otherwise. The only possible
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reason for failure is an unsupported value for \fIround\fP, which is signalled
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by setting errno to EINVAL.
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.SH DIAGNOSTICS
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fegetround always succeeds. The only possible reason for failure of fesetround
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is an unsupported value for \fIround\fP, which is signalled by setting errno to
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EINVAL.
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.SH "SEE ALSO"
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nearbyint(3)
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