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Re: newbie question....
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From:
Brent "Dax" Royal-Gordon
Date:
March 12, 2004 13:59
Subject:
Re: newbie question....
Matt Greenwood wrote:
> Firstly, you have made an assumption that the addition here is
> equivalent to OR and carry, which may be correct for certain
> representations of integral datatypes, but certainly isn't for any
> kind of floating point arithmetic that I know of.
True enough, but I think I got my point across--concatenation is a
fundamentally different operation from addition.
> Secondly, you missed the point that I was making. The current add
> opcodes defined in parrot are the following:
>
(various combinations of PMC, INT, and NUM)
>
> I was simply asking why there wasn't an
>
> add(out STR, in STR, in STR)
>
> which seems reasonable. This is not a question of operator
> overloading, but rather semantics - that's all.
I suppose that depends on what you want it to do. If you want it to
convert $2 and $3 to integers, add them, convert the result to a string,
and put it in $1, then the answer is "that's not a common enough
operation to warrant adding the extra opcodes"--especially since the
I/S/N registers aren't supposed to be used for anything but optimizations.
If you want it to concatenate $2 and $3 and insert the result into $1,
and remove the "concat" opcode altogether...well, the answer stems from
the existence of add(in PMC, in PMC, in PMC). What should that
do--integer addition, or string concatenation? Remember, some of our
languages don't overload add for strings. We need a separate concat(in
PMC, in PMC, in PMC), so we might as well have concat(out STR, in STR,
in STR) too.
--
Brent "Dax" Royal-Gordon <brent@brentdax.com>
Perl and Parrot hacker
Oceania has always been at war with Eastasia.
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