intdoc.texi

gcc-2.95.3 Linux下最常用的C编译器

@end ifset
@ifset familyF77
@node CExp Intrinsic
@subsubsection CExp Intrinsic
@cindex CExp intrinsic
@cindex intrinsics, CExp

@noindent
@example
CExp(@var{X})
@end example

@noindent
CExp: @code{COMPLEX(KIND=1)} function.

@noindent
@var{X}: @code{COMPLEX(KIND=1)}; scalar; INTENT(IN).

@noindent
Intrinsic groups: (standard FORTRAN 77).

@noindent
Description:

Archaic form of @code{EXP()} that is specific
to one type for @var{X}.
@xref{Exp Intrinsic}.

@node Char Intrinsic
@subsubsection Char Intrinsic
@cindex Char intrinsic
@cindex intrinsics, Char

@noindent
@example
Char(@var{I})
@end example

@noindent
Char: @code{CHARACTER*1} function.

@noindent
@var{I}: @code{INTEGER}; scalar; INTENT(IN).

@noindent
Intrinsic groups: (standard FORTRAN 77).

@noindent
Description:

Returns the character corresponding to the
code specified by @var{I}, using the system's
native character set.

Because the system's native character set is used,
the correspondence between character and their codes
is not necessarily the same between GNU Fortran
implementations.

Note that no intrinsic exists to convert a numerical
value to a printable character string.
For example, there is no intrinsic that, given
an @code{INTEGER} or @code{REAL} argument with the
value @samp{154}, returns the @code{CHARACTER}
result @samp{'154'}.

Instead, you can use internal-file I/O to do this kind
of conversion.
For example:

@smallexample
INTEGER VALUE
CHARACTER*10 STRING
VALUE = 154
WRITE (STRING, '(I10)'), VALUE
PRINT *, STRING
END
@end smallexample

The above program, when run, prints:

@smallexample
        154
@end smallexample

@xref{IChar Intrinsic}, for the inverse of the @code{CHAR} function.

@xref{AChar Intrinsic}, for the function corresponding
to the ASCII character set.

@end ifset
@ifset familyF2U
@node ChDir Intrinsic (subroutine)
@subsubsection ChDir Intrinsic (subroutine)
@cindex ChDir intrinsic
@cindex intrinsics, ChDir

@noindent
@example
CALL ChDir(@var{Dir}, @var{Status})
@end example

@noindent
@var{Dir}: @code{CHARACTER}; scalar; INTENT(IN).

@noindent
@var{Status}: @code{INTEGER(KIND=1)}; OPTIONAL; scalar; INTENT(OUT).

@noindent
Intrinsic groups: @code{unix}.

@noindent
Description:

Sets the current working directory to be @var{Dir}.
If the @var{Status} argument is supplied, it contains 0
on success or a non-zero error code otherwise upon return.
See @code{chdir(3)}.

@emph{Caution:} Using this routine during I/O to a unit connected with a
non-absolute file name can cause subsequent I/O on such a unit to fail
because the I/O library might reopen files by name.

Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine, or do not support the
(optional) @var{Status} argument.

For information on other intrinsics with the same name:
@xref{ChDir Intrinsic (function)}.

@end ifset
@ifset familyBADU77
@node ChDir Intrinsic (function)
@subsubsection ChDir Intrinsic (function)
@cindex ChDir intrinsic
@cindex intrinsics, ChDir

@noindent
@example
ChDir(@var{Dir})
@end example

@noindent
ChDir: @code{INTEGER(KIND=1)} function.

@noindent
@var{Dir}: @code{CHARACTER}; scalar; INTENT(IN).

@noindent
Intrinsic groups: @code{badu77}.

@noindent
Description:

Sets the current working directory to be @var{Dir}.
Returns 0 on success or a non-zero error code.
See @code{chdir(3)}.

@emph{Caution:} Using this routine during I/O to a unit connected with a
non-absolute file name can cause subsequent I/O on such a unit to fail
because the I/O library might reopen files by name.

Due to the side effects performed by this intrinsic, the function
form is not recommended.

For information on other intrinsics with the same name:
@xref{ChDir Intrinsic (subroutine)}.

@end ifset
@ifset familyF2U
@node ChMod Intrinsic (subroutine)
@subsubsection ChMod Intrinsic (subroutine)
@cindex ChMod intrinsic
@cindex intrinsics, ChMod

@noindent
@example
CALL ChMod(@var{Name}, @var{Mode}, @var{Status})
@end example

@noindent
@var{Name}: @code{CHARACTER}; scalar; INTENT(IN).

@noindent
@var{Mode}: @code{CHARACTER}; scalar; INTENT(IN).

@noindent
@var{Status}: @code{INTEGER(KIND=1)}; OPTIONAL; scalar; INTENT(OUT).

@noindent
Intrinsic groups: @code{unix}.

@noindent
Description:

Changes the access mode of file @var{Name} according to the
specification @var{Mode}, which is given in the format of
@code{chmod(1)}.
A null character (@samp{CHAR(0)}) marks the end of
the name in @var{Name}---otherwise,
trailing blanks in @var{Name} are ignored.
Currently, @var{Name} must not contain the single quote
character.

If the @var{Status} argument is supplied, it contains
0 on success or a non-zero error code upon return.

Note that this currently works
by actually invoking @code{/bin/chmod} (or the @code{chmod} found when
the library was configured) and so might fail in some circumstances and
will, anyway, be slow.

Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine, or do not support the
(optional) @var{Status} argument.

For information on other intrinsics with the same name:
@xref{ChMod Intrinsic (function)}.

@end ifset
@ifset familyBADU77
@node ChMod Intrinsic (function)
@subsubsection ChMod Intrinsic (function)
@cindex ChMod intrinsic
@cindex intrinsics, ChMod

@noindent
@example
ChMod(@var{Name}, @var{Mode})
@end example

@noindent
ChMod: @code{INTEGER(KIND=1)} function.

@noindent
@var{Name}: @code{CHARACTER}; scalar; INTENT(IN).

@noindent
@var{Mode}: @code{CHARACTER}; scalar; INTENT(IN).

@noindent
Intrinsic groups: @code{badu77}.

@noindent
Description:

Changes the access mode of file @var{Name} according to the
specification @var{Mode}, which is given in the format of
@code{chmod(1)}.
A null character (@samp{CHAR(0)}) marks the end of
the name in @var{Name}---otherwise,
trailing blanks in @var{Name} are ignored.
Currently, @var{Name} must not contain the single quote
character.

Returns 0 on success or a non-zero error code otherwise.

Note that this currently works
by actually invoking @code{/bin/chmod} (or the @code{chmod} found when
the library was configured) and so might fail in some circumstances and
will, anyway, be slow.

Due to the side effects performed by this intrinsic, the function
form is not recommended.

For information on other intrinsics with the same name:
@xref{ChMod Intrinsic (subroutine)}.

@end ifset
@ifset familyF77
@node CLog Intrinsic
@subsubsection CLog Intrinsic
@cindex CLog intrinsic
@cindex intrinsics, CLog

@noindent
@example
CLog(@var{X})
@end example

@noindent
CLog: @code{COMPLEX(KIND=1)} function.

@noindent
@var{X}: @code{COMPLEX(KIND=1)}; scalar; INTENT(IN).

@noindent
Intrinsic groups: (standard FORTRAN 77).

@noindent
Description:

Archaic form of @code{LOG()} that is specific
to one type for @var{X}.
@xref{Log Intrinsic}.

@node Cmplx Intrinsic
@subsubsection Cmplx Intrinsic
@cindex Cmplx intrinsic
@cindex intrinsics, Cmplx

@noindent
@example
Cmplx(@var{X}, @var{Y})
@end example

@noindent
Cmplx: @code{COMPLEX(KIND=1)} function.

@noindent
@var{X}: @code{INTEGER}, @code{REAL}, or @code{COMPLEX}; scalar; INTENT(IN).

@noindent
@var{Y}: @code{INTEGER} or @code{REAL}; OPTIONAL (must be omitted if @var{X} is @code{COMPLEX}); scalar; INTENT(IN).

@noindent
Intrinsic groups: (standard FORTRAN 77).

@noindent
Description:

If @var{X} is not type @code{COMPLEX},
constructs a value of type @code{COMPLEX(KIND=1)} from the
real and imaginary values specified by @var{X} and
@var{Y}, respectively.
If @var{Y} is omitted, @samp{0.} is assumed.

If @var{X} is type @code{COMPLEX},
converts it to type @code{COMPLEX(KIND=1)}.

@xref{Complex Intrinsic}, for information on easily constructing
a @code{COMPLEX} value of arbitrary precision from @code{REAL}
arguments.

@end ifset
@ifset familyGNU
@node Complex Intrinsic
@subsubsection Complex Intrinsic
@cindex Complex intrinsic
@cindex intrinsics, Complex

@noindent
@example
Complex(@var{Real}, @var{Imag})
@end example

@noindent
Complex: @code{COMPLEX} function, the exact type being the result of cross-promoting the
types of all the arguments.

@noindent
@var{Real}: @code{INTEGER} or @code{REAL}; scalar; INTENT(IN).

@noindent
@var{Imag}: @code{INTEGER} or @code{REAL}; scalar; INTENT(IN).

@noindent
Intrinsic groups: @code{gnu}.

@noindent
Description:

Returns a @code{COMPLEX} value that has @samp{Real} and @samp{Imag} as its
real and imaginary parts, respectively.

If @var{Real} and @var{Imag} are the same type, and that type is not
@code{INTEGER}, no data conversion is performed, and the type of
the resulting value has the same kind value as the types
of @var{Real} and @var{Imag}.

If @var{Real} and @var{Imag} are not the same type, the usual type-promotion
rules are applied to both, converting either or both to the
appropriate @code{REAL} type.
The type of the resulting value has the same kind value as the
type to which both @var{Real} and @var{Imag} were converted, in this case.

If @var{Real} and @var{Imag} are both @code{INTEGER}, they are both converted
to @code{REAL(KIND=1)}, and the result of the @code{COMPLEX()}
invocation is type @code{COMPLEX(KIND=1)}.

@emph{Note:} The way to do this in standard Fortran 90
is too hairy to describe here, but it is important to
note that @samp{CMPLX(D1,D2)} returns a @code{COMPLEX(KIND=1)}
result even if @samp{D1} and @samp{D2} are type @code{REAL(KIND=2)}.
Hence the availability of @code{COMPLEX()} in GNU Fortran.

@end ifset
@ifset familyF77
@node Conjg Intrinsic
@subsubsection Conjg Intrinsic
@cindex Conjg intrinsic
@cindex intrinsics, Conjg

@noindent
@example
Conjg(@var{Z})
@end example

@noindent
Conjg: @code{COMPLEX} function, the @samp{KIND=} value of the type being that of argument @var{Z}.

@noindent
@var{Z}: @code{COMPLEX}; scalar; INTENT(IN).

@noindent
Intrinsic groups: (standard FORTRAN 77).

@noindent
Description:

Returns the complex conjugate:

@example
COMPLEX(REALPART(@var{Z}), -IMAGPART(@var{Z}))
@end example

@node Cos Intrinsic
@subsubsection Cos Intrinsic
@cindex Cos intrinsic
@cindex intrinsics, Cos

@noindent
@example
Cos(@var{X})
@end example

@noindent
Cos: @code{REAL} or @code{COMPLEX} function, the exact type being that of argument @var{X}.

@noindent
@var{X}: @code{REAL} or @code{COMPLEX}; scalar; INTENT(IN).

@noindent
Intrinsic groups: (standard FORTRAN 77).

@noindent
Description:

Returns the cosine of @var{X}, an angle measured
in radians.

@xref{ACos Intrinsic}, for the inverse of this function.

@end ifset
@ifset familyVXT
@node CosD Intrinsic
@subsubsection CosD Intrinsic
@cindex CosD intrinsic
@cindex intrinsics, CosD

This intrinsic is not yet implemented.
The name is, however, reserved as an intrinsic.
Use @samp{EXTERNAL CosD} to use this name for an
external procedure.

@end ifset
@ifset familyF77
@node CosH Intrinsic
@subsubsection CosH Intrinsic
@cindex CosH intrinsic
@cindex intrinsics, CosH

@noindent
@example
CosH(@var{X})
@end example

@noindent
CosH: @code{REAL} function, the @samp{KIND=} value of the type being that of argument @var{X}.

@noindent
@var{X}: @code{REAL}; scalar; INTENT(IN).

@noindent
Intrinsic groups: (standard FORTRAN 77).

@noindent
Description:

Returns the hyperbolic cosine of @var{X}.

@end ifset
@ifset familyF90
@node Count Intrinsic
@subsubsection Count Intrinsic
@cindex Count intrinsic
@cindex intrinsics, Count

This intrinsic is not yet implemented.
The name is, however, reserved as an intrinsic.
Use @samp{EXTERNAL Count} to use this name for an
external procedure.

@node CPU_Time Intrinsic
@subsubsection CPU_Time Intrinsic
@cindex CPU_Time intrinsic
@cindex intrinsics, CPU_Time

@noindent
@example
CALL CPU_Time(@var{Seconds})
@end example

@noindent
@var{Seconds}: @code{REAL}; scalar; INTENT(OUT).

@noindent
Intrinsic groups: @code{f90}.

@noindent
Description:

Returns in @var{Seconds} the current value of the system time.
This implementation of the Fortran 95 intrinsic is just an alias for
@code{second} @xref{Second Intrinsic (subroutine)}.

@cindex wraparound, timings
@cindex limits, timings
On some systems, the underlying timings are represented
using types with sufficiently small limits that overflows
(wraparounds) are possible, such as 32-bit types.
Therefore, the values returned by this intrinsic
might be, or become, negative,
or numerically less than previous values,