• Russell Lewis (9/9) Sep 25 2002 I am writing some D code where I have some arrays that must always
• Mac Reiter (19/28) Sep 25 2002 The fact that the assert will remove the code during a release build cha...
• Russell Lewis (4/47) Sep 25 2002 You're right that array.sort would give me a sorted array without having...
• Walter (8/11) Sep 29 2002 A couple observations - I think Mac is correct in that testing to see if...

Russell Lewis <spamhole-2001-07-16 deming-os.org> writes:

I am writing some D code where I have some arrays that must always 
remain sorted.  So I'm adding asserts periodically to make sure that my 
arrays are sorted.  Currently, I'm doing this:

assert(array[] == array.dup.sort);

But it would be nicer to just have the compiler provide a boolean property:

assert(array.sorted);

Of course, that would not be an actual variable in the array 
reference...instead, the compiler would iterate through the array and 
confirm that the array is sorted (or not), and return the answer.

Mac Reiter <Mac_member pathlink.com> writes:

In article <3D91DE98.5060905 deming-os.org>, Russell Lewis says...
I am writing some D code where I have some arrays that must always 
remain sorted.  So I'm adding asserts periodically to make sure that my 
arrays are sorted.  Currently, I'm doing this:

assert(array[] == array.dup.sort);

But it would be nicer to just have the compiler provide a boolean property:

assert(array.sorted);

Of course, that would not be an actual variable in the array 
reference...instead, the compiler would iterate through the array and 
confirm that the array is sorted (or not), and return the answer.

The fact that the assert will remove the code during a release build changes the
following argument, but I'll throw it out there anyway:

If, instead of "assert()", you were doing "if()", then I would suggest that
making the test is unnecessary and inefficient.  If you do:

if (! array.sorted)
{
array.sort;
}

you would be better off just using:

array.sort;

The first code makes one linear pass, followed by a sorting if needed.  The
second code does either one linear pass or a sorting, but never both.

Of course, if you are only using this in your asserts to make sure that your
other code is behaving properly, then your release build won't have any of this,
and what you're doing is fine.

You could make a template with a "bit sorted(in T[])" query function in it, I
suppose.  The property would be nicer, though.

Mac

Russell Lewis <spamhole-2001-07-16 deming-os.org> writes:

Mac Reiter wrote:
 In article <3D91DE98.5060905 deming-os.org>, Russell Lewis says...
 
I am writing some D code where I have some arrays that must always 
remain sorted.  So I'm adding asserts periodically to make sure that my 
arrays are sorted.  Currently, I'm doing this:

assert(array[] == array.dup.sort);

But it would be nicer to just have the compiler provide a boolean property:

assert(array.sorted);

Of course, that would not be an actual variable in the array 
reference...instead, the compiler would iterate through the array and 
confirm that the array is sorted (or not), and return the answer.

 
 
 The fact that the assert will remove the code during a release build changes
the
 following argument, but I'll throw it out there anyway:
 
 If, instead of "assert()", you were doing "if()", then I would suggest that
 making the test is unnecessary and inefficient.  If you do:
 
 if (! array.sorted)
 {
 array.sort;
 }
 
 you would be better off just using:
 
 array.sort;
 
 The first code makes one linear pass, followed by a sorting if needed.  The
 second code does either one linear pass or a sorting, but never both.
 
 Of course, if you are only using this in your asserts to make sure that your
 other code is behaving properly, then your release build won't have any of
this,
 and what you're doing is fine.
 
 You could make a template with a "bit sorted(in T[])" query function in it, I
 suppose.  The property would be nicer, though.
 
 Mac

You're right that array.sort would give me a sorted array without having 
to test first.  But I'd like to be able to get an up/down validation of 
"is my program correct or not"

"Walter" <walter digitalmars.com> writes:

"Russell Lewis" <spamhole-2001-07-16 deming-os.org> wrote in message
news:3D92257A.7010104 deming-os.org...
 You're right that array.sort would give me a sorted array without having
 to test first.  But I'd like to be able to get an up/down validation of
 "is my program correct or not"

A couple observations - I think Mac is correct in that testing to see if an
array is sorted is inherent in sorting an array, so there is little
efficiency to be gained by testing first. Testing for sort is a great idea
for a contract, but contracts don't need to operate efficiently, so your one
liner to do it (which is clever, I wouldn't have thought of it) is up to the
job.