[fpc-pascal] Can variables be declared within a block?

[Frank Church]

On 18 October 2010 14:55, Frank Church <vfclists at gmail.com> wrote:

>
>
> On 18 October 2010 14:42, Florian Klaempfl <florian at freepascal.org> wrote:
>
>> Am 18.10.2010 14:58, schrieb Frank Church:
>> >
>> >
>> > On 18 October 2010 07:49, Florian Klaempfl <florian at freepascal.org
>> > <mailto:florian at freepascal.org>> wrote:
>> >
>> >     Am 18.10.2010 08:17, schrieb Zaher Dirkey:
>> >     >
>> >     >
>> >     > On Thu, Oct 14, 2010 at 11:21 AM, Michael Van Canneyt
>> >     > <michael at freepascal.org <mailto:michael at freepascal.org>
>> >     <mailto:michael at freepascal.org <mailto:michael at freepascal.org>>>
>> wrote:
>> >     >
>> >     >
>> >     >
>> >     >     On Thu, 14 Oct 2010, Frank Church wrote:
>> >     >
>> >     >         Can variables be declared within a begin end block?
>> >     >
>> >     >
>> >     >     No.
>> >     >
>> >
>> >
>> > That is a rather emphatic no :).
>> >  Is there some performance or other related reason why it is a bad idea?
>>
>> It's just a matter of readability, e.g. having a variable declared in
>> two blocks with the same name can cause you a lot of headache:
>>
>> procedure p;
>>
>> begin
>>  ...
>>  begin
>>    var i : integer;
>>    ...
>>    ...
>>    ...
>>    i:=12341234;
>>    ...
>>    ...
>>    ...
>>    ...
>>  end;
>>  ...
>>  ...
>>  ...
>>  begin
>>    var i : integer;
>>    ...
>>    writeln(i); <--- this i is not the same as above so i does not
>> contain 12341234 but it contains probably some garbage.
>>  end;
>>
>
>
> My need is not for such kind or variables - it is for something like this.
>
> say I have some thing like:
>  StringList.NameOfIndex(TableName.FieldByName('xxxx').AsString) >
> AnotherEqualLongExpression + SomeOtherEvenLongerExpression.
>
> I just want to create shorter variables like
> si :=  StringList.NameOfIndex(TableName.FieldByName('xxxx').AsString);
> ae := xxx;
> so:= yyy
>
> to express complicated logic with them.
>
> When I put them all at the top of the procedure, they are extra noise,
> which is not necessary for the understanding the purpose at the top level of
> the procedure.
>
> I understand the need to avoid stuff that could create unintended errors
> and have experienced such issues before. I will be careful not to use the
> more than enough rope I have been given to hang myself. I promise :)
>
>

I sometimes use nested procedures for such purposes when it comes to the
program logic itself, having something like that for variables would be
nice.

PS. The promise above should be "we promise" :)


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>>
>
>
>
> --
> Frank Church
>
> =======================
> http://devblog.brahmancreations.com
>



-- 
Frank Church

=======================
http://devblog.brahmancreations.com
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