[fpc-devel] Fwd: While - Otherwise Statement
lazarus at mfriebe.de
Mon Oct 12 00:41:49 CEST 2015
On 11/10/2015 22:33, Tomas Hajny wrote:
> On Sun, October 11, 2015 22:48, Sven Barth wrote:
>> That "then" is a great idea! That would definitely not break anything and
>> it would make sense indeed:
>> === code begin ===
>> while bool do
>> until bool then
>> === code end ===
> I'm afraid that I got lost in this discussion, but what exactly would be
> the supposed semantic difference between the behaviour compared to
> situation when there was a semicolon instead of 'then' there?
You mean compared to the otherwise solution?
The following is currently valid code:
case a of
2: while a > 0 do dec(a) // no semicolon
write('a was neither 1 nor 2');
This code would continue to compile, but it would change meaning/behaviour.
So if somebody has code like that, in a million line project, which
fails after otherwise was introduced, then it could be a long search for
why it fails. (Easy to fix once found, but hard to find)
Besides "then" makes more sense (as in reading it as english description).
Both else/otherwise, to me read as: If the while block before was not
executed at all.
while a > 0 do write
reads to me "halt" is an alternative to the "while". It gets executed if
the while was never executde (a was already <= 0 when while was reached
"then" in english may mean "after that" and that is what happens here.
After the while do something.
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