Re: Record operations (Algebraic Data Types and printing)

[Niklas Holsti <niklas.holsti@tidorum.invalid>]

On 18-10-05 20:46 , Henrik Härkönen wrote:
> Hi! (Very) Slowly getting my Ada wheels rolling, didn't get the book
> yet etc. but anyway...
>
> I'm coming from Scala world most recently and I like to leverage
> Algebraic Data Types (through sealed traits), or Discriminated
> Unions, as they were called in F#. I was happy to find out that Ada
> has Variant Record, which I believe pretty much covers the same
> thing. Maybe in a bit more verbose way. :) I'm somehow fascinated by
> the possibility to carry state as the type, thus with different data
> items for each state.
>
> Now as I'm playing with the records, I'd like to print them out, just
> for "debugging" purposes. Is there any convenient way to splash them
> out in console? Some sort of default string representation?

Nope, and too bad. That's something that would often be useful at the 
program development stage. But not so useful when the program is in 
production runs, for typical Ada applications.

One way to get something like this is to run the program under a 
debugger, and ask the debugger to display the record variable. Debuggers 
can usually show "component-name = value" pairs.

> Seems that 'Image attribute works only for scalar types.

Indeed.

I seem to remember seeing a posting here, a few years ago, offering a 
tool that would construct an Image function for a given record type. The 
tool was possibly based on ASIS, and possibly not. Sadly I did not find 
any links to this, but perhaps someone else has a better memory or 
better search methods.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .