boolean array

boolean array

[Keith]

Hello,

I want to know if there is any false element(s) in an array of booleans.

Currently I am looping through the array and looking at each value until
I find a false element.

x := true;
for i in foo'range loop      -- foo'range < 8
   x := foo (i);
   exit when not x;
end loop;

if x then .....

Is there a faster/preferred way of accomplishing this?
I am compiling Ada 95 with Green Hills AdaMULTI for VxWorks running on x86.  

Thank you,
Keith

Re: boolean array

[Christoph Grein]

    Foo : array (some_range) of Boolean;
    ...
    Any_False_Present : constant Boolean := Foo /= (some_range => True);

But faster/preferred ??

> Hello,
> 
> I want to know if there is any false element(s) in an array of booleans.
> 
> Currently I am looping through the array and looking at each value until
> I find a false element.
> 
> x := true;
> for i in foo'range loop      -- foo'range < 8
>    x := foo (i);
>    exit when not x;
> end loop;
> 
> if x then .....
> 
> Is there a faster/preferred way of accomplishing this?
> I am compiling Ada 95 with Green Hills AdaMULTI for VxWorks running on x86.  
> 
> Thank you,
> Keith

Re: boolean array

[Sandro Binetti]

yokwad@yahoo.com (Keith) wrote in message news:<b28112f8.0201241633.7baa1010@posting.google.com>...
> Hello,
> 
> I want to know if there is any false element(s) in an array of booleans.
> 
> Currently I am looping through the array and looking at each value until
> I find a false element.
> 
> x := true;
> for i in foo'range loop      -- foo'range < 8
>    x := foo (i);
>    exit when not x;
> end loop;
> 

if foo/=(foo'range=>TRUE) then ...

Bye, Sandro.

Re: boolean array

[Robert Dewar]

Christoph Grein <christoph.grein@eurocopter.com> wrote in message news:<mailman.1011938222.12962.comp.lang.ada@ada.eu.org>...
> Foo : array (some_range) of Boolean;
>     ...
>     Any_False_Present : constant Boolean := Foo /= (some_range => True);
> 
> But faster/preferred ??

If the array is packed, this should be fast. Here using the
latest version of GNAT, is a source program:

  procedure K is
    type Rng is range 1 .. 8;
    type a is array (Rng) of Boolean;
    pragma Pack (a);
    va : a := (1 => False, others => True);

  begin
     if va = (Rng => True) then 
        null;
     end if;
  end;

And here is the expanded source program:

  procedure k is
     type k__rng is range 1 .. 8;
     type k__a is array (1 .. 8) of boolean;
     pragma pack (k__a);
     va : k__a := k__T6b!(16#FE#);
  begin
     if va = k__T10b!(16#FF#) then
        null;
     end if;
     return;
  end k;

The ! here is unchecked conversion, and the implementation
type of va is an 8 bit unsigned number, so as you can see
this reduces the cost to a single comparison instruction.

For those who need to see the asm to be convinced, here 
it is:

	.file	"k.adb"
gcc2_compiled.:
___gnu_compiled_ada:
.text
	.align 2
.globl __ada_k
__ada_k:
	pushl %ebp
	movl %esp,%ebp
	subl $4,%esp
	movb $254,-1(%ebp)
	cmpb $255,-1(%ebp)
	jne L2
L2:
	jmp L1
	.align 2,0x90
L1:
	leave
	ret