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From: Jos De Laender <jos.de_laender@alcatel.be>
Subject: Re: Newbie question : types , representation
Date: 1999/08/25
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    Thanks,

this was really very to the point for what concerns my problem !
I learned from it.
Some small comments furtheron between your text.

Best regards,

Jos

Brian Rogoff wrote:

> If you know that characters are the same size as your "byte" type, be it
> an Interfaces.Unsigned_8 or a System.Storage_Element then it should be OK
> to use Unchecked_Conversion if you're worried about the overhead of a
> conversion function, but I really can't imagine any overhead even from a
> safe type conversion if you turn checking off, which you really must do if
> you want to compare with C. I don't understand why you think there is some
> table lookup involved.

I think here I was partly wrong. The table lookup is needed for the original
algorithm where I got the problem (base64 decoding) , but it is equally needed
in C as in ADA. So forget indeed this one ...

>
>
> Part of the problem with C and Ada comparisons is that every C operation is
> unchecked, whereas in Ada everything is checked by default. You have to
> know enough about your Ada compiler to turn off those checks when doing
> the performance comparisons.

I realize this extremely well ! As I told you I do know VHDL quite well , and I
have to use always this same explanation to explain the 'C is faster crowd'
that when comparing the same functionality , including the checking , it isn't.

>
>
> -- Brian

  Jos De Laender