MASK(3I) Last changed: 1-6-98
NAME
_mask, _maskl, _maskr, MASK - Returns a bit maskSYNOPSIS
C/C++:
#include <intrinsics.h>
long _mask (long i);
long _maskl (long i);
long _maskr (long i);
Fortran:
MASK ([I=]i)
IMPLEMENTATION
C/C++: UNICOS and UNICOS/mk systems
Fortran: UNICOS, UNICOS/mk, and IRIX systems
STANDARDS
C/C++: Cray Research extension
Fortran: CF90 and MIPSpro 7 Fortran 90 compiler extension to Fortran
90
C/C++ DESCRIPTION
The _mask function forms a mask of bits set to 1, left-justified or
right-justified. If 0 <= i <= 63, a left-justified mask of bits set
to 1, i bits long, is formed. Otherwise, a right-justified mask of
bits set to 1, (128 - i) bits long, is formed. Value i must be in the
range of 0 through 128.
The _maskl function returns a left-justified mask of i bits set to 1.
Value i must be in the range of 0 through 64.
The _maskr function returns a right-justified mask of i bits set to 1.
Value i must be in the range of 0 through 64.
Because these are intrinsic functions, no externally visible library
functions are available for them. The compiler generates inline code
to produce the result.
FORTRAN DESCRIPTION
The MASK function returns a bit mask of 1's.
On UNICOS systems, the argument is a 64-bit integer.
On UNICOS/mk systems, the argument is a 32-bit or 64-bit integer.
On IRIX systems, the argument is an 8-bit, 16-bit, 32-bit, or 64-bit
integer.
It accepts the following argument:
i In Fortran, this must be an integer argument, as follows:
* If i is an 8-bit object, i must be in the range 0 <= i <= 16.
* If i is a 16-bit object, i must be in the range 0 <= i <= 32.
* If i is a 32-bit object, i must be in the range 0 <= i <= 64.
* If i is a 64-bit object, i must be in the range 0 <= i <= 128.
MASK is an elemental function. The name of this function cannot be
passed as an argument.
This is an outmoded routine. Refer to the Fortran Language Reference
Manual, Volume 2, publication SR-3903, for information about outmoded
features and their preferred standard alternatives.
RETURN VALUES
In C/C++, the mask functions return a 64-bit object.
In Fortran, MASK returns a Boolean result on UNICOS and UNICOS/mk
systems. It returns an integer result on IRIX systems.
When i is a 64-bit object, the return values are of the following
form:
* If i is in the range 0 <= i <= 64, a left-justified mask of i bits
is returned.
* If i is in the range 65 <= i <= 128, a right-justified mask of (128
- i) bits is returned.
When i is a 32-bit object, the return values are of the following
form:
* If i is in the range 0 <= i <= 32, a left-justified mask of i bits
is returned.
* If i is in the range 33 <= i <= 64, a right-justified mask of (64 -
i) bits is returned.
When i is a 16-bit object, the return values are of the following
form:
* If i is in the range 0 <= i <= 16, a left-justified mask of i bits
is returned.
* If i is in the range 17 <= i <= 32, a right-justified mask of (32 -
i) bits is returned.
When i is a 8-bit object, the return values are of the following form:
* If i is in the range 0 <= i <= 8, a left-justified mask of i bits is
returned.
* If i is in the range 7 <= i <= 16, a right-justified mask of (16 -
i) bits is returned.
EXAMPLES
Fortran: The following section of Fortran code shows the MASK
function used with several different arguments. The bit patterns of
the results are given.
INTEGER I1, I2, I3
...
I1 = MASK(3)
I2 = MASK(64)
I3 = MASK(127)-----------------------------------------------------
| 1 | 1 | 1 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 |
-----------------------------------------------------
I1
---------------------------------------------
| 1 | 1 | 1 | 1 | ... | 1 | 1 | 1 | 1 |
---------------------------------------------
I2
---------------------------------------------
| 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 1 |
---------------------------------------------
I3
SEE ALSO
A complete list of C/C++ intrinsic functions available on Cray
Research systems is in the Cray C/C++ Reference Manual, publication SR
-2179.
Intrinsic Procedures Reference Manual, publication SR-2138, for the
printed version of this man page.
