[fpc-pascal] Re: Changing variable in conditional

Mark Morgan Lloyd markMLl.fpc-pascal at telemetry.co.uk
Thu Jan 10 12:43:50 CET 2013

leledumbo wrote:
>> If Pascal /had/ to have some sort of multiple assignment, I'd have 
> thought borrowing an idea from Perl and doing something like 
> [a, b, c] := (d = e); 
> would have been minimally acceptable. 
> I would pick from Lua instead, it looks cleaner. Well... I'll make it
> stricter though, by making the number of elements on both side must equal.
> e.g.:
> a,b,c := v1,v2,v3;
> a,b := b,a; // value swapping

I admit that I was- in large part- borrowing from APL. In other words, 
if the number of elements on both sides of the expression is the same 
you get a one-to-one correspondence but if the RHS only has a single 
element it's expanded. APL will also do things comparable with treating

[a, b, c, a] := [1, 2];

as though it really was

[a, b, c, a] := [1, 2, 1, 2];

but that's getting well outside what's reasonable particularly since APL 
makes a point of not defining the order of internal operations (i.e. the 
final value of a is, at best, implementation-defined).

However as I said: it's not Pascal :-)

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

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

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