Matching elements of records
Mon Nov 1 09:39:44 CET 2004
IMHO, it is still a matter of taste. (For the record, I prefer
the variable to the right.)
"Richard A. O'Keefe" <> writes:
> (A) Consistency with other functional programming languages, ...
> ML, Haskell
The best of the arguments.
> (B) The linguistic argument. In fact this has two versions. One is
> "heavy constituent comes later". The other is "most salient
> constituent comes first". To me, when you have an as-pattern,
> the most salient part is the name. That's the "topic"; the
> restrictive pattern is the "comment".
In a head, I see the matching as the most important thing, and binding
to a variable as an afterthought just because I'll need the entire term
later (perhaps much later) in the body.
> (C) CONSISTENCY WITH USE (1) OF = IN ERLANG.
> To me it is simply inconsistent to bind X in the body of a function
> by writing
> X = [Y|Ys]
This is how you build a new list in a body.
> and then to turn around and do the exact OPPOSITE in the head of
> a function by writing
> [Y|Ys] = X
That's the way you do matching in a body.
Why would you want a matching in head look like it was an assignment
X = [Y|Ys]
in a body?
which is can be seen to be a matching regardless of context.
Björn Gustavsson, Erlang/OTP, Ericsson AB
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