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gcc-2.95.3 Linux下最常用的C编译器

DEFDOC (DSIGN, "Apply sign to magnitude (archaic).", ARCHAIC_2 (SIGN, Sign))
DEFDOC (ISIGN, "Apply sign to magnitude (archaic).", ARCHAIC_2 (SIGN, Sign))

DEFDOC (REAL, "Convert value to type @code{REAL(KIND=1)}.", "\
Converts @var{@1@} to @code{REAL(KIND=1)}.

Use of @code{@0@()} with a @code{COMPLEX} argument
(other than @code{COMPLEX(KIND=1)}) is restricted to the following case:

@example
REAL(REAL(@1@))
@end example

@noindent
This expression converts the real part of @1@ to
@code{REAL(KIND=1)}.

@xref{RealPart Intrinsic}, for information on a GNU Fortran
intrinsic that extracts the real part of an arbitrary
@code{COMPLEX} value.

@xref{REAL() and AIMAG() of Complex}, for more information.
")

DEFDOC (DREAL, "Convert value to type @code{REAL(KIND=2)}.", "\
Converts @var{@1@} to @code{REAL(KIND=2)}.

If @var{@1@} is type @code{COMPLEX}, its real part
is converted (if necessary) to @code{REAL(KIND=2)},
and its imaginary part is disregarded.

Although this intrinsic is not standard Fortran,
it is a popular extension offered by many compilers
that support @code{DOUBLE COMPLEX}, since it offers
the easiest way to extract the real part of a @code{DOUBLE COMPLEX}
value without using the Fortran 90 @code{REAL()} intrinsic
in a way that produces a return value inconsistent with
the way many FORTRAN 77 compilers handle @code{REAL()} of
a @code{DOUBLE COMPLEX} value.

@xref{RealPart Intrinsic}, for information on a GNU Fortran
intrinsic that avoids these areas of confusion.

@xref{Dble Intrinsic}, for information on the standard FORTRAN 77
replacement for @code{DREAL()}.

@xref{REAL() and AIMAG() of Complex}, for more information on
this issue.
")

DEFDOC (IMAGPART, "Extract imaginary part of complex.", "\
The imaginary part of @var{@1@} is returned, without conversion.

@emph{Note:} The way to do this in standard Fortran 90
is @samp{AIMAG(@var{@1@})}.
However, when, for example, @var{@1@} is @code{DOUBLE COMPLEX},
@samp{AIMAG(@var{@1@})} means something different for some compilers
that are not true Fortran 90 compilers but offer some
extensions standardized by Fortran 90 (such as the
@code{DOUBLE COMPLEX} type, also known as @code{COMPLEX(KIND=2)}).

The advantage of @code{@0@()} is that, while not necessarily
more or less portable than @code{AIMAG()}, it is more likely to
cause a compiler that doesn't support it to produce a diagnostic
than generate incorrect code.

@xref{REAL() and AIMAG() of Complex}, for more information.
")

DEFDOC (COMPLEX, "Build complex value from real and@99@imaginary parts.", "\
Returns a @code{COMPLEX} value that has @samp{@1@} and @samp{@2@} as its
real and imaginary parts, respectively.

If @var{@1@} and @var{@2@} 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{@1@} and @var{@2@}.

If @var{@1@} and @var{@2@} 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{@1@} and @var{@2@} were converted, in this case.

If @var{@1@} and @var{@2@} are both @code{INTEGER}, they are both converted
to @code{REAL(KIND=1)}, and the result of the @code{@0@()}
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.
")

DEFDOC (LOC, "Address of entity in core.", "\
The @code{LOC()} intrinsic works the
same way as the @code{%LOC()} construct.
@xref{%LOC(),,The @code{%LOC()} Construct}, for
more information.
")

DEFDOC (REALPART, "Extract real part of complex.", "\
The real part of @var{@1@} is returned, without conversion.

@emph{Note:} The way to do this in standard Fortran 90
is @samp{REAL(@var{@1@})}.
However, when, for example, @var{@1@} is @code{COMPLEX(KIND=2)},
@samp{REAL(@var{@1@})} means something different for some compilers
that are not true Fortran 90 compilers but offer some
extensions standardized by Fortran 90 (such as the
@code{DOUBLE COMPLEX} type, also known as @code{COMPLEX(KIND=2)}).

The advantage of @code{@0@()} is that, while not necessarily
more or less portable than @code{REAL()}, it is more likely to
cause a compiler that doesn't support it to produce a diagnostic
than generate incorrect code.

@xref{REAL() and AIMAG() of Complex}, for more information.
")

DEFDOC (GETARG, "Obtain command-line argument.", "\
Sets @var{@2@} to the @var{@1@}-th command-line argument (or to all
blanks if there are fewer than @var{@2@} command-line arguments);
@code{CALL @0@(0, @var{value})} sets @var{value} to the name of the
program (on systems that support this feature).

@xref{IArgC Intrinsic}, for information on how to get the number
of arguments.
")

DEFDOC (ABORT, "Abort the program.", "\
Prints a message and potentially causes a core dump via @code{abort(3)}.
")

DEFDOC (EXIT, "Terminate the program.", "\
Exit the program with status @var{@1@} after closing open Fortran
I/O units and otherwise behaving as @code{exit(2)}.
If @var{@1@} is omitted the canonical `success' value
will be returned to the system.
")

DEFDOC (IARGC, "Obtain count of command-line arguments.", "\
Returns the number of command-line arguments.

This count does not include the specification of the program
name itself.
")

DEFDOC (CTIME_func, "Convert time to Day Mon dd hh:mm:ss yyyy.", "\
Converts @var{@1@}, a system time value, such as returned by
@code{TIME8()}, to a string of the form @samp{Sat Aug 19 18:13:14 1995},
and returns that string as the function value.

@xref{Time8 Intrinsic}.
")

DEFDOC (CTIME_subr, "Convert time to Day Mon dd hh:mm:ss yyyy.", "\
Converts @var{@1@}, a system time value, such as returned by
@code{TIME8()}, to a string of the form @samp{Sat Aug 19 18:13:14 1995},
and returns that string in @var{@2@}.

@xref{Time8 Intrinsic}.

Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine.
")

DEFDOC (DATE, "Get current date as dd-Mon-yy.", "\
Returns @var{@1@} in the form @samp{@var{dd}-@var{mmm}-@var{yy}},
representing the numeric day of the month @var{dd}, a three-character
abbreviation of the month name @var{mmm} and the last two digits of
the year @var{yy}, e.g.@: @samp{25-Nov-96}.

@cindex Y2K compliance
@cindex Year 2000 compliance
This intrinsic is not recommended, due to the year 2000 approaching.
Therefore, programs making use of this intrinsic
might not be Year 2000 (Y2K) compliant.
@xref{CTime Intrinsic (subroutine)}, for information on obtaining more digits
for the current (or any) date.
")

DEFDOC (DTIME_func, "Get elapsed time since last time.", "\
Initially, return the number of seconds of runtime
since the start of the process's execution
as the function value,
and the user and system components of this in @samp{@var{@1@}(1)}
and @samp{@var{@1@}(2)} respectively.
The functions' value is equal to @samp{@var{@1@}(1) + @var{@1@}(2)}.

Subsequent invocations of @samp{@0@()} return values accumulated since the
previous invocation.

@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,
during a single run of the compiled program.

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

DEFDOC (DTIME_subr, "Get elapsed time since last time.", "\
Initially, return the number of seconds of runtime
since the start of the process's execution
in @var{@2@},
and the user and system components of this in @samp{@var{@1@}(1)}
and @samp{@var{@1@}(2)} respectively.
The value of @var{@2@} is equal to @samp{@var{@1@}(1) + @var{@1@}(2)}.

Subsequent invocations of @samp{@0@()} set values based on accumulations
since the previous invocation.

@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,
during a single run of the compiled program.

Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine.
")

DEFDOC (ETIME_func, "Get elapsed time for process.", "\
Return the number of seconds of runtime
since the start of the process's execution
as the function value,
and the user and system components of this in @samp{@var{@1@}(1)}
and @samp{@var{@1@}(2)} respectively.
The functions' value is equal to @samp{@var{@1@}(1) + @var{@1@}(2)}.

@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,
during a single run of the compiled program.
")

DEFDOC (ETIME_subr, "Get elapsed time for process.", "\
Return the number of seconds of runtime
since the start of the process's execution
in @var{@2@},
and the user and system components of this in @samp{@var{@1@}(1)}
and @samp{@var{@1@}(2)} respectively.
The value of @var{@2@} is equal to @samp{@var{@1@}(1) + @var{@1@}(2)}.

@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,
during a single run of the compiled program.

Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine.
")

DEFDOC (FDATE_func, "Get current time as Day Mon dd hh:mm:ss yyyy.", "\
Returns the current date (using the same format as @code{CTIME()}).

Equivalent to:

@example
CTIME(TIME8())
@end example

@cindex Y10K compliance
@cindex Year 10000 compliance
@cindex wraparound, Y10K
@cindex limits, Y10K
Programs making use of this intrinsic
might not be Year 10000 (Y10K) compliant.
For example, the date might appear,
to such programs, to wrap around
(change from a larger value to a smaller one)
as of the Year 10000.

@xref{CTime Intrinsic (function)}.
")

DEFDOC (FDATE_subr, "Get current time as Day Mon dd hh:mm:ss yyyy.", "\
Returns the current date (using the same format as @code{CTIME()})
in @var{@1@}.

Equivalent to:

@example
CALL CTIME(@var{@1@}, TIME8())
@end example

@cindex Y10K compliance
@cindex Year 10000 compliance
@cindex wraparound, Y10K
@cindex limits, Y10K
Programs making use of this intrinsic
might not be Year 10000 (Y10K) compliant.
For example, the date might appear,
to such programs, to wrap around
(change from a larger value to a smaller one)
as of the Year 10000.

@xref{CTime Intrinsic (subroutine)}.

Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine.
")

DEFDOC (GMTIME, "Convert time to GMT time info.", "\
Given a system time value @var{@1@}, fills @var{@2@} with values
extracted from it appropriate to the GMT time zone using
@code{gmtime(3)}.

The array elements are as follows:

@enumerate
@item
Seconds after the minute, range 0--59 or 0--61 to allow for leap
seconds

@item
Minutes after the hour, range 0--59

@item
Hours past midnight, range 0--23

@item
Day of month, range 0--31

@item
Number of months since January, range 0--12

@item
Years since 1900

@item
Number of days since Sunday, range 0--6

@item
Days since January 1

@item
Daylight savings indicator: positive if daylight savings is in effect,
zero if not, and negative if the information isn't available.
@end enumerate
")

DEFDOC (LTIME, "Convert time to local time info.", "\
Given a system time value @var{@1@}, fills @var{@2@} with values
extracted from it appropriate to the GMT time zone using
@code{localtime(3)}.

The array elements are as follows:

@enumerate
@item
Seconds after the minute, range 0--59 or 0--61 to allow for leap
seconds

@item
Minutes after the hour, range 0--59

@item
Hours past midnight, range 0--23

@item
Day of month, range 0--31

@item
Number of months since January, range 0--12

@item
Years since 1900

@item
Number of days since Sunday, range 0--6

@item
Days since January 1

@item
Daylight savings indicator: positive if daylight savings is in effect,
zero if not, and negative if the information isn't available.
@end enumerate
")

DEFDOC (IDATE_unix, "Get local time info.", "\
Fills @var{@1@} with the numerical values at the current local time
of day, month (in the range 1--12), and year in elements 1, 2, and 3,
respectively.
The year has four significant digits.

@cindex Y10K compliance
@cindex Year 10000 compliance
@cindex wraparound, Y10K
@cindex limits, Y10K
Programs making use of this intrinsic
might not be Year 10000 (Y10K) compliant.
For example, the date might appear,
to such programs, to wrap around
(change from a larger value to a smaller one)
as of the Year 10000.
")

DEFDOC (IDATE_vxt, "Get local time info (VAX/VMS).", "\
Returns the numerical values of the current local time.
The month (in the range 1--12) is returned in @var{@1@},
the day (in the range 1--7) in @var{@2@},
and the year in @var{@3@} (in the range 0--99).

@cindex Y2K compliance
@cindex Year 2000 compliance
@cindex wraparound, Y2K
@cindex limits, Y2K
This intrinsic is not recommended, due to the year 2000 approaching.
Therefore, programs making use of this intrinsic
might not be Year 2000 (Y2K) compliant.
For example, the date might appear,
to such programs, to wrap around
(change from a larger value to a smaller one)
as of the Year 2000.

@xref{IDate Intrinsic (UNIX)}, for information on obtaining more digits
for the current date.
")