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D - Should This Be Legal?

reply Russ Lewis <spamhole-2001-07-16 deming-os.org> writes:
I was doing a search through an array, and I wanted to assert that I
definitely would find what I was looking for in the array.  So I coded
this, which crashed DLI 0.1.1:

for(int foo=0; assert(foo<array.length); foo++)
  if(do_test(array[foo]))
    do_stuff();

Is this be legal?  If not, why not?

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Nov 01 2002
next sibling parent reply Burton Radons <loth users.sourceforge.net> writes:
Russ Lewis wrote:

 I was doing a search through an array, and I wanted to assert that I
 definitely would find what I was looking for in the array.  So I coded
 this, which crashed DLI 0.1.1:
 
 for(int foo=0; assert(foo<array.length); foo++)
   if(do_test(array[foo]))
     do_stuff();
 
 Is this be legal?  If not, why not?



assert isn't an expression, so no.  This assertion is redundant anyway - 
in normal builds the array[foo] will do a bounds check, in release 
builds neither will be checked.
Nov 01 2002
parent reply Russ Lewis <spamhole-2001-07-16 deming-os.org> writes:
Burton Radons wrote:


 Russ Lewis wrote:

 I was doing a search through an array, and I wanted to assert that I
 definitely would find what I was looking for in the array.  So I coded
 this, which crashed DLI 0.1.1:

 for(int foo=0; assert(foo<array.length); foo++)
   if(do_test(array[foo]))
     do_stuff();

 Is this be legal?  If not, why not?



 assert isn't an expression, so no.  This assertion is redundant anyway -
 in normal builds the array[foo] will do a bounds check, in release
 builds neither will be checked.



ACK!!!!  I forgot the key thing in the whole code!

There was supposed to be a break if you match the test:

for(int foo=0; assert(foo<array.length); foo++)
  if(do_test(array[foo]))
  {
    do_stuff();
    break;
  }

Does that make more sense now?
--
The Villagers are Online! http://villagersonline.com

.[ (the fox.(quick,brown)) jumped.over(the dog.lazy) ]
.[ (a version.of(English).(precise.more)) is(possible) ]
?[ you want.to(help(develop(it))) ]
Nov 01 2002
parent Burton Radons <loth users.sourceforge.net> writes:
Russ Lewis wrote:

 Burton Radons wrote:
 
 

Russ Lewis wrote:


I was doing a search through an array, and I wanted to assert that I
definitely would find what I was looking for in the array.  So I coded
this, which crashed DLI 0.1.1:

for(int foo=0; assert(foo<array.length); foo++)
  if(do_test(array[foo]))
    do_stuff();

Is this be legal?  If not, why not?



assert isn't an expression, so no.  This assertion is redundant anyway -
in normal builds the array[foo] will do a bounds check, in release
builds neither will be checked.



 
 ACK!!!!  I forgot the key thing in the whole code!
 
 There was supposed to be a break if you match the test:
 
 for(int foo=0; assert(foo<array.length); foo++)
   if(do_test(array[foo]))
   {
     do_stuff();
     break;
   }
 
 Does that make more sense now?



I understood what you meant.  It turns out assert is an expression - I 
assume to allow chaining with comma - but it's still incorrect here as 
it returns void.  I throw an error on the occasion now.

I don't think it's a common enough form to have it in the language.
Nov 01 2002
prev sibling parent "Mike Wynn" <mike.wynn l8night.co.uk> writes:
"Russ Lewis" <spamhole-2001-07-16 deming-os.org> wrote in message
news:3DC2903C.660DA40C deming-os.org...

 I was doing a search through an array, and I wanted to assert that I
 definitely would find what I was looking for in the array.  So I coded
 this, which crashed DLI 0.1.1:

 for(int foo=0; assert(foo<array.length); foo++)
   if(do_test(array[foo]))
     do_stuff();

 Is this be legal?  If not, why not?



apart from assert not being an expression
assert is a check for something that is NOT expected to happen and should
compile to nothing when non assert builds are built.
here quite clearly foo can be larger than array.length;

I assume your code should have been (where getting to the end would be an
error)
for(int foo=0; assert(foo<array.length); foo++)
   if(do_test(array[foo]))
     break;
arrays should be bounds checked in asserting builds (IMHO)

also asserts SHOULD not have side effects
the code
foo = 0;
do {
    assert( ++foo < array.length );
    count += array[foo];
} while( count < 100 );

should be a compiler warning (modification withing an assert)

Mike.
Nov 01 2002