intrinsic.texi

理解和实践操作系统的一本好书

may be any concatenation of @code{"r"} (readable), @code{"w"} (writable)
and @code{"x"} (executable), or @code{" "} to check for existence.
@end multitable

@item @emph{Return value}:
Returns a scalar @code{INTEGER}, which is @code{0} if the file is
accessible in the given mode; otherwise or if an invalid argument
has been given for @code{MODE} the value @code{1} is returned.

@item @emph{Example}:
@smallexample
program access_test
  implicit none
  character(len=*), parameter :: file  = 'test.dat'
  character(len=*), parameter :: file2 = 'test.dat  '//achar(0)
  if(access(file,' ') == 0) print *, trim(file),' is exists'
  if(access(file,'r') == 0) print *, trim(file),' is readable'
  if(access(file,'w') == 0) print *, trim(file),' is writable'
  if(access(file,'x') == 0) print *, trim(file),' is executable'
  if(access(file2,'rwx') == 0) &
    print *, trim(file2),' is readable, writable and executable'
end program access_test
@end smallexample
@item @emph{Specific names}:
@item @emph{See also}:

@end table



@node ACHAR
@section @code{ACHAR} --- Character in @acronym{ASCII} collating sequence 
@fnindex ACHAR
@cindex @acronym{ASCII} collating sequence
@cindex collating sequence, @acronym{ASCII}

@table @asis
@item @emph{Description}:
@code{ACHAR(I)} returns the character located at position @code{I}
in the @acronym{ASCII} collating sequence.

@item @emph{Standard}:
F77 and later

@item @emph{Class}:
Elemental function

@item @emph{Syntax}:
@code{RESULT = ACHAR(I)}

@item @emph{Arguments}:
@multitable @columnfractions .15 .70
@item @var{I} @tab The type shall be @code{INTEGER(*)}.
@end multitable

@item @emph{Return value}:
The return value is of type @code{CHARACTER} with a length of one.  The
kind type parameter is the same as  @code{KIND('A')}.

@item @emph{Example}:
@smallexample
program test_achar
  character c
  c = achar(32)
end program test_achar
@end smallexample

@item @emph{Note}:
See @ref{ICHAR} for a discussion of converting between numerical values
and formatted string representations.

@item @emph{See also}:
@ref{CHAR}, @ref{IACHAR}, @ref{ICHAR}

@end table



@node ACOS
@section @code{ACOS} --- Arccosine function 
@fnindex ACOS
@fnindex DACOS
@cindex trigonometric function, cosine, inverse
@cindex cosine, inverse

@table @asis
@item @emph{Description}:
@code{ACOS(X)} computes the arccosine of @var{X} (inverse of @code{COS(X)}).

@item @emph{Standard}:
F77 and later

@item @emph{Class}:
Elemental function

@item @emph{Syntax}:
@code{RESULT = ACOS(X)}

@item @emph{Arguments}:
@multitable @columnfractions .15 .70
@item @var{X} @tab The type shall be @code{REAL(*)} with a magnitude that is
less than one.
@end multitable

@item @emph{Return value}:
The return value is of type @code{REAL(*)} and it lies in the
range @math{ 0 \leq \acos(x) \leq \pi}. The kind type parameter 
is the same as @var{X}.

@item @emph{Example}:
@smallexample
program test_acos
  real(8) :: x = 0.866_8
  x = acos(x)
end program test_acos
@end smallexample

@item @emph{Specific names}:
@multitable @columnfractions .20 .20 .20 .25
@item Name            @tab Argument          @tab Return type       @tab Standard
@item @code{DACOS(X)} @tab @code{REAL(8) X}  @tab @code{REAL(8)}    @tab F77 and later
@end multitable

@item @emph{See also}:
Inverse function: @ref{COS}

@end table



@node ACOSH
@section @code{ACOSH} --- Hyperbolic arccosine function
@fnindex ACOSH
@fnindex DACOSH
@cindex area hyperbolic cosine
@cindex hyperbolic arccosine
@cindex hyperbolic function, cosine, inverse
@cindex cosine, hyperbolic, inverse

@table @asis
@item @emph{Description}:
@code{ACOSH(X)} computes the hyperbolic arccosine of @var{X} (inverse of
@code{COSH(X)}).

@item @emph{Standard}:
GNU extension

@item @emph{Class}:
Elemental function

@item @emph{Syntax}:
@code{RESULT = ACOSH(X)}

@item @emph{Arguments}:
@multitable @columnfractions .15 .70
@item @var{X} @tab The type shall be @code{REAL(*)} with a magnitude that is
greater or equal to one.
@end multitable

@item @emph{Return value}:
The return value is of type @code{REAL(*)} and it lies in the
range @math{0 \leq \acosh (x) \leq \infty}.

@item @emph{Example}:
@smallexample
PROGRAM test_acosh
  REAL(8), DIMENSION(3) :: x = (/ 1.0, 2.0, 3.0 /)
  WRITE (*,*) ACOSH(x)
END PROGRAM
@end smallexample

@item @emph{Specific names}:
@multitable @columnfractions .20 .20 .20 .25
@item Name             @tab Argument          @tab Return type       @tab Standard
@item @code{DACOSH(X)} @tab @code{REAL(8) X}  @tab @code{REAL(8)}    @tab GNU extension
@end multitable

@item @emph{See also}:
Inverse function: @ref{COSH}
@end table



@node ADJUSTL
@section @code{ADJUSTL} --- Left adjust a string 
@fnindex ADJUSTL
@cindex string, adjust left
@cindex adjust string

@table @asis
@item @emph{Description}:
@code{ADJUSTL(STR)} will left adjust a string by removing leading spaces.
Spaces are inserted at the end of the string as needed.

@item @emph{Standard}:
F95 and later

@item @emph{Class}:
Elemental function

@item @emph{Syntax}:
@code{RESULT = ADJUSTL(STR)}

@item @emph{Arguments}:
@multitable @columnfractions .15 .70
@item @var{STR} @tab The type shall be @code{CHARACTER}.
@end multitable

@item @emph{Return value}:
The return value is of type @code{CHARACTER} where leading spaces 
are removed and the same number of spaces are inserted on the end
of @var{STR}.

@item @emph{Example}:
@smallexample
program test_adjustl
  character(len=20) :: str = '   gfortran'
  str = adjustl(str)
  print *, str
end program test_adjustl
@end smallexample

@item @emph{See also}:
@ref{ADJUSTR}, @ref{TRIM}
@end table



@node ADJUSTR
@section @code{ADJUSTR} --- Right adjust a string 
@fnindex ADJUSTR
@cindex string, adjust right
@cindex adjust string

@table @asis
@item @emph{Description}:
@code{ADJUSTR(STR)} will right adjust a string by removing trailing spaces.
Spaces are inserted at the start of the string as needed.

@item @emph{Standard}:
F95 and later

@item @emph{Class}:
Elemental function

@item @emph{Syntax}:
@code{RESULT = ADJUSTR(STR)}

@item @emph{Arguments}:
@multitable @columnfractions .15 .70
@item @var{STR} @tab The type shall be @code{CHARACTER}.
@end multitable

@item @emph{Return value}:
The return value is of type @code{CHARACTER} where trailing spaces 
are removed and the same number of spaces are inserted at the start
of @var{STR}.

@item @emph{Example}:
@smallexample
program test_adjustr
  character(len=20) :: str = 'gfortran'
  str = adjustr(str)
  print *, str
end program test_adjustr
@end smallexample

@item @emph{See also}:
@ref{ADJUSTL}, @ref{TRIM}
@end table



@node AIMAG
@section @code{AIMAG} --- Imaginary part of complex number  
@fnindex AIMAG
@fnindex DIMAG
@fnindex IMAG
@fnindex IMAGPART
@cindex complex numbers, imaginary part

@table @asis
@item @emph{Description}:
@code{AIMAG(Z)} yields the imaginary part of complex argument @code{Z}.
The @code{IMAG(Z)} and @code{IMAGPART(Z)} intrinsic functions are provided
for compatibility with @command{g77}, and their use in new code is 
strongly discouraged.

@item @emph{Standard}:
F77 and later, has overloads that are GNU extensions

@item @emph{Class}:
Elemental function

@item @emph{Syntax}:
@code{RESULT = AIMAG(Z)}

@item @emph{Arguments}:
@multitable @columnfractions .15 .70
@item @var{Z} @tab The type of the argument shall be @code{COMPLEX(*)}.
@end multitable

@item @emph{Return value}:
The return value is of type real with the
kind type parameter of the argument.

@item @emph{Example}:
@smallexample
program test_aimag
  complex(4) z4
  complex(8) z8
  z4 = cmplx(1.e0_4, 0.e0_4)
  z8 = cmplx(0.e0_8, 1.e0_8)
  print *, aimag(z4), dimag(z8)
end program test_aimag
@end smallexample

@item @emph{Specific names}:
@multitable @columnfractions .20 .20 .20 .25
@item Name            @tab Argument            @tab Return type       @tab Standard
@item @code{DIMAG(Z)} @tab @code{COMPLEX(8) Z} @tab @code{REAL(8)}    @tab GNU extension
@item @code{IMAG(Z)}  @tab @code{COMPLEX(*) Z} @tab @code{REAL(*)}    @tab GNU extension
@item @code{IMAGPART(Z)} @tab @code{COMPLEX(*) Z} @tab @code{REAL(*)} @tab GNU extension
@end multitable
@end table



@node AINT
@section @code{AINT} --- Truncate to a whole number
@fnindex AINT
@fnindex DINT
@cindex floor
@cindex rounding, floor

@table @asis
@item @emph{Description}:
@code{AINT(X [, KIND])} truncates its argument to a whole number.

@item @emph{Standard}:
F77 and later

@item @emph{Class}:
Elemental function

@item @emph{Syntax}:
@code{RESULT = AINT(X [, KIND])} 

@item @emph{Arguments}:
@multitable @columnfractions .15 .70
@item @var{X}    @tab The type of the argument shall be @code{REAL(*)}.
@item @var{KIND} @tab (Optional) An @code{INTEGER(*)} initialization
                      expression indicating the kind parameter of
		      the result.
@end multitable

@item @emph{Return value}:
The return value is of type real with the kind type parameter of the
argument if the optional @var{KIND} is absent; otherwise, the kind
type parameter will be given by @var{KIND}.  If the magnitude of 
@var{X} is less than one, then @code{AINT(X)} returns zero.  If the
magnitude is equal to or greater than one, then it returns the largest
whole number that does not exceed its magnitude.  The sign is the same
as the sign of @var{X}. 

@item @emph{Example}:
@smallexample
program test_aint
  real(4) x4
  real(8) x8
  x4 = 1.234E0_4
  x8 = 4.321_8
  print *, aint(x4), dint(x8)
  x8 = aint(x4,8)
end program test_aint
@end smallexample

@item @emph{Specific names}:
@multitable @columnfractions .20 .20 .20 .25
@item Name           @tab Argument         @tab Return type      @tab Standard
@item @code{DINT(X)} @tab @code{REAL(8) X} @tab @code{REAL(8)}   @tab F77 and later
@end multitable
@end table



@node ALARM
@section @code{ALARM} --- Execute a routine after a given delay
@fnindex ALARM
@cindex delayed execution

@table @asis
@item @emph{Description}:
@code{ALARM(SECONDS, HANDLER [, STATUS])} causes external subroutine @var{HANDLER}
to be executed after a delay of @var{SECONDS} by using @code{alarm(2)} to
set up a signal and @code{signal(2)} to catch it. If @var{STATUS} is
supplied, it will be returned with the number of seconds remaining until
any previously scheduled alarm was due to be delivered, or zero if there
was no previously scheduled alarm.

@item @emph{Standard}:
GNU extension

@item @emph{Class}:
Subroutine

@item @emph{Syntax}:
@code{CALL ALARM(SECONDS, HANDLER [, STATUS])}

@item @emph{Arguments}:
@multitable @columnfractions .15 .70
@item @var{SECONDS} @tab The type of the argument shall be a scalar
@code{INTEGER}. It is @code{INTENT(IN)}.
@item @var{HANDLER} @tab Signal handler (@code{INTEGER FUNCTION} or
@code{SUBROUTINE}) or dummy/global @code{INTEGER} scalar. The scalar 
values may be either @code{SIG_IGN=1} to ignore the alarm generated 
or @code{SIG_DFL=0} to set the default action. It is @code{INTENT(IN)}.
@item @var{STATUS}  @tab (Optional) @var{STATUS} shall be a scalar
variable of the default @code{INTEGER} kind. It is @code{INTENT(OUT)}.
@end multitable

@item @emph{Example}:
@smallexample
program test_alarm
  external handler_print
  integer i
  call alarm (3, handler_print, i)
  print *, i
  call sleep(10)
end program test_alarm
@end smallexample