[fpc-pascal] Record operator for assignment

[Mark Morgan Lloyd]

On 28/04/17 04:30, Ryan Joseph wrote:
> Instead of making constructors and doing busy work It would be nice if Free Pascal could let you assign records outside of type blocks like:
> rec := (x: 0; y: 0; z: 0);
> Why isn’t this possible btw? I saw some C++ code do this and it seems like an obvious solution that should have existed 20 years ago. The feature exists for type blocks so why not just enable it for other parts of code?
> I had another idea to make this a little simpler by using open arrays and operator overloading. The compiler doesn’t permit this however. Is it a bug, my code or just a limitation?

Curiously, I was up against exactly the same thing yesterday when 
setting up an array for GetLongOpts() and a table for tokenising some 
other text elements.

I ended up using a dynamic array and overloading + for the first of 
those since it allowed me to do

   with option do begin
     name := 'block';
     value := name[1]   <===
   end;
   theOpts += option;

which wouldn't be available at compilation time, and also since 
build-time directives could easily include/exclude options. For the 
other one I used an array of records.

The problem with arrays of records as I see it is that the number of 
elements has to be predefined:

const   TopMatchItem= 10;

type    TMatchItem= record
                       name: string;
                       field: TCSVField
                     end;
         TAMatchItem= array[0..TopMatchItem] of TMatchItem;

const   matchItems: TAMatchItem= ((name: ''; field: CSVBad),
                       (name: 'block'; field: CSVBlock),
..

Or from the FPC compiler itself:

   ttokenarray=array[ttoken] of tokenrec;
   ptokenarray=^ttokenarray;
..

const
   arraytokeninfo : ttokenarray =(
       (str:''              ;special:true ;keyword:[m_none];op:NOTOKEN),
..

Is there any way that the length of an array being used for that sort of 
job can be defined by what's put into it, rather than having to be 
predefined?

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]