exp.3m

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3M 代码 · 共 207 行

.\" SCCSID: @(#)exp.3m	6.2	8/30/89
.TH exp 3m VAX
.SH Name
exp, expm1, log, log10, log1p, pow, sqrt \- exponential, logarithm, power, square root
.SH Syntax
.nf
.B #include <math.h>
.PP
.B double exp(\fIx\fP)
.B double \fIx\fP;
.PP
.B double expm1(\fIx\fP)
.B double \fIx\fP;
.PP
.B double log(\fIx\fP)
.B double \fIx\fP;
.PP
.B double log10(\fIx\fP)
.B double \fIx\fP;
.PP
.B double log1p(\fIx\fP)
.B double \fIx\fP;
.PP
.B double pow(\fIx,y\fP)
.B double \fIx,y\fP;
.PP
.B double sqrt(\fIx\fP)
.B double \fIx\fP;
.fi
.SH Description
.NXR "exp subroutine (math)"
.NXR "expm1 subroutine (math)"
.NXR "log subroutine (math)"
.NXR "log10 subroutine (math)"
.NXR "log1p subroutine (math)"
.NXR "pow subroutine"
.NXR "sqrt subroutine (math)"
.NXR "exp subroutine (math)" "erf subroutine"
.NXR "exponential function"
.NXR "logarithm function"
.NXR "power function"
.NXR "square root function"
The 
.PN exp
function returns the exponential function of 
.I x.
.PP
The
.PN expm1 
function
returns exp(\fIx\fP)-1 accurately even for tiny 
.IR x .
.PP
The
.PN log
function returns the natural logarithm of 
.IR x ;
.PN log10
returns the base 10 logarithm.
.PP
The
.PN log1p
function returns log(1+\fIx\fP) accurately even for tiny
.IR x .
.PP
The
.PN pow
function returns
.I  x
raised to the
.I y
power.
.PP
The
.PN sqrt
function returns the square root of 
.I x.
.SH Return Values
The
.PN exp
function returns HUGE_VAL and sets
.I errno
to ERANGE when the correct value would overflow.
When the correct value would underflow it returns zero and
.I errno
is set to ERANGE.
.PP
The
.PN expm1
function returns HUGE_VAL and sets
.I errno
to ERANGE when the correct value would overflow.
When the correct value would underflow it returns \-1.
.PP
The
.PN log
and
.PN log10
functions return \-HUGE_VAL and set
.I errno
to EDOM when
.I x
is less than or equal to zero.
When the correct value would overflow flow they return \-HUGE_VAL and
.I errno
is set to ERANGE.
.PP
The
.PN log1p
function returns \-HUGE_VAL and sets
.I errno
to EDOM when
.I x
is less than or equal to \-1.
When the correct value would overflow flow it returns \-HUGE_VAL and
.I errno
is set to ERANGE.
.PP
The
.PN pow
function has many special cases.
When
.I x
and
.I y
are both zero it returns 1.0.
When
.I x
is negative and
.I y
is not an integer value it returns zero and
.I errno
is set to EDOM.
When
.I x
is zero and
.I y
is negative it returns \-HUGE_VAL and
.I errno
is set to EDOM.
When the correct value would overflow HUGE_VAL is returned and
.I errno
is set to ERANGE.
When the correct value would underflow zero is returned and
.I errno
is set to ERANGE.
.PP
The
.PN sqrt
function returns zero and sets
.I errno
to EDOM when
.I x
is negative.
.SH Environment
.NXR "exp subroutine (math)" "System V and"
When your program is compiled using the System V environment,
.PN exp
returns HUGE when the correct value would overflow, 
and sets \fIerrno\fP to ERANGE; 
.PN exp
returns zero when the correct value would 
underflow, and sets errno to ERANGE.
.PP
The
.PN log
and 
.PN log10
functions return HUGE and set \fIerrno\fP to EDOM
when 
.I x
is nonpositive.  An error message is printed on
the standard error output.
.PP
The
.PN pow
function returns zero and sets \fIerrno\fP to EDOM when 
.I x
is non-positive and y is not an integer, or when
.I x
and
.I y
are both zero.  In these cases, a message indicating
DOMAIN error is printed on the standard error output.
When the correct value for
.PN pow
would overflow,
.PN pow
returns HUGE and sets \fIerrno\fP to ERANGE.
.PP
The
.PN sqrt
function returns zero and sets \fIerrno\fP to EDOM when 
.I x 
is negative.  A message indicating DOMAIN error is 
printed on the standard error output.
.PP
These error-handling procedures may be changed with 
the function
.MS matherr 3m .
.PP
.NT
DOMAIN error is only printed in the System V environment.
.NE
.SH See Also
hypot(3m), intro(3m), sinh(3m)