[fpc-pascal] using functions from units & main programme

[John Lee]

Thanks for the fix, but it makes the code a bit more complicated than I'd
hoped/thought based on my (over simple?) impression that local fns are used
in place of those in units. John

On 18 November 2011 16:55, Sven Barth <pascaldragon at googlemail.com> wrote:

> Am 18.11.2011 17:47, schrieb John Lee:
>
>  Sorry for confusion, my email wasn't clear...
>> old fpc version, that I have to use because of availability of various
>> units...Free Pascal Compiler version 2.2.2 [2008/08/03] for i386
>>
>> this is jim.pp---
>> unit jim;
>> interface
>>  function fna:string;
>>  function fnb:string;
>>
>> implementation
>> function fna:string;
>> begin
>>  fna:='jim';
>> end;
>> function fnb:string;
>> begin
>>  fnb:=fna;
>> end;
>> end.
>>
>> this is fred.pp---
>> uses jim;
>>
>> function fna:string;
>> begin
>>  fna:='fred';
>> end;
>>
>> begin
>>  writeln(fnb);
>> end.
>>
>> This writeln gives jim, ie the version in jim - I'd like it to be fred &
>> thought that it would! What can I do please, to _force_ fnb to use the
>> fred version of fna?
>>
>
> As I said per se this is expected, because the "jnb" in "jim" only knows
> about the "jna" in "jim", but not about the "jna" in your main program.
>
> Possible solution:
>
> Extend your unit "jim" the following way (this is the "function variable"
> approach I mentioned):
>
> === unit jim begin ===
>
> unit jim;
>
> interface
>
> type
>  TStringFunc = function: String;
>
> function fna: String;
> function fnb(aFunc: TStringFunc = Nil): String;
>
> implementation
>
> function fna: String;
>
> begin
>  fna := 'jim';
> end;
>
> function fnb(aFunc: TStringFunc): String;
> begin
>  if Assigned(aFunc) then
>    fnb := aFunc
>  else
>    fnb := fna;
> end;
>
> end.
>
> === unit jim end ===
>
> And your main program will then look like this:
>
> === main program begin ===
>
> uses jim;
>
> function fna: String;
>
> begin
>  fna := 'fred';
> end;
>
> begin
>  writeln(fnb(@fna)); // will print "fred"
>  writeln(fnb); // will print "jim"
> end.
>
> === main program end ===
>
> For further information about procedure/function variables I refer you to
> the documentation: http://www.freepascal.org/**docs-html/ref/refse17.html#
> **x45-520003.6<http://www.freepascal.org/docs-html/ref/refse17.html#x45-520003.6>
>
> Of course you are free to ask further questions if you need help on this
> or another topic. ;)
>
>
> Regards,
> Sven
> ______________________________**_________________
> fpc-pascal maillist  -  fpc-pascal at lists.freepascal.**org<fpc-pascal at lists.freepascal.org>
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>
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