公共接口运算符(<=)
如果set1和set2中的位相同，或者最高阶不同的位在set1中设置为0，在set2中设置为1，则返回.true.，否则返回.false.。这些集合必须具有相同数量的位，否则结果未定义。（规范）
示例
program example_le
use stdlib_bitsets
type(bitset_64) :: set0, set1, set2
call set0 % init( 33 )
call set1 % init( 33 )
call set2 % init( 33 )
call set1 % set( 0 )
call set2 % set( 32 )
if ( set0 <= set1 .and. set1 <= set2 .and. set0 <= set2 .and. &
set0 <= set0 .and. set1 <= set1 .and. set2 <= set2 .and. &
.not. set1 <= set0 .and. .not. set2 <= set0 .and. .not. &
set2 <= set1 ) then
write(*,*) 'Passed 64 bit less than or equal tests.'
else
error stop 'Failed 64 bit less than or equal tests.'
end if
end program example_le