[fpc-pascal] Feature proposal: function-based assignment operators

[Benito van der Zander]

>
> There was already a discussion some time ago whether we should allow 
> operators like "or=" and such as well and the result was simple: no. I 
> consider this the same here. 

But it would be more consistent with +=

> You can achieve a similar effect through type helpers in 2.7.1 though: 
looks cool, but I only have 2.6.2...

>
>
> type
>   TLongIntHelper = type helper for LongInt
>     procedure Min(aValue: LongInt);
>   end;
>
> procedure TLongIntHelper.Min(aValue: LongInt);
> begin
>   Self := Math.Min(Self, aValue);
> end; 

Perhaps that should be defined in the rtl


On 03/28/2013 05:47 PM, Sven Barth wrote:
> Am 28.03.2013 16:23, schrieb Benito van der Zander:
>> Hi,
>> quite often you need to change a value relatively to another value.
>> For example:
>>
>>   array1[array2[i]] := array1[array2[i]] + 42;
>>
>> Luckily this can be written as
>>
>>   array1[array2[i]] += 42;
>>
>> Which is nice.
>>
>> However, sometimes you do not need addition, but the minimum.
>> For example:
>>
>>    array1[array2[i]] := min(array1[array2[i]], 42);
>>
>> Now, you need to repeat all the array indices.
>>
>> Which is very ugly.
>>
>> So there should be an alternative syntax, similar to += :
>> I.e.:
>>
>>    array1[array2[i]] min= 42;
>>
>>
>> More generally, if func is a 2-ary function, of type type(a) => 
>> type(b) => type(a), the syntax
>>
>> a func= b
>>
>> should become a := func(a, b)
>>
>> (Or alternatively the syntax   a : func = b;  might be easier to parse)
>>
> There was already a discussion some time ago whether we should allow 
> operators like "or=" and such as well and the result was simple: no. I 
> consider this the same here.
>
> You can achieve a similar effect through type helpers in 2.7.1 though:
>
> === code begin ===
>
> program mintest;
>
> {$mode objfpc}
>
> uses
>   Math;
>
> type
>   TLongIntHelper = type helper for LongInt
>     procedure Min(aValue: LongInt);
>   end;
>
> procedure TLongIntHelper.Min(aValue: LongInt);
> begin
>   Self := Math.Min(Self, aValue);
> end;
>
> var
>   arr: array[0..20] of LongInt;
>   i: LongInt;
> begin
>   for i := Low(arr) to High(arr) do
>     arr[i] := i;
>
>   for i := Low(arr) to High(arr) do
>     Write(arr[i], ' ');
>   Writeln;
>
>   arr[15].Min(10); // arr[15] is passed as Self to Min
>
>   for i := Low(arr) to High(arr) do
>     Write(arr[i], ' ');
>   Writeln;
> end.
>
> === code end ===
>
> Regards,
> Sven
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