[erlang-questions] style question - best way to test multiple non-guard conditions sequentially

Anthony Ramine n.oxyde@REDACTED
Tue Jul 16 03:16:52 CEST 2013

I disagree.

In the case of 'if', the tests are disjunctions of conjunctions of guards; whereas in the case of 'cond' they should be boolean tests. So what is a valid 'if' clause may not be a 'cond' one.

Furthermore, in the case of 'if', the fact that foobar just fails silently is because guard semantics are used: the very thing that is not used in 'cond' expressions.

Anthony Ramine

Le 16 juil. 2013 à 00:30, Richard A. O'Keefe a écrit :

> When there is a choice between two constructs such as
> 	if G -> Bt ; true -> Bf end
> and	case {} of {} when G -> Bt ; {} when true -> Bf end
> that *LOOKS* as though it is purely stylistic,
> it should *BE* purely stylistic.
> Consider
> 	if E -> Bt ; true -> Bf end
> and
> 	cond E -> Bt ; true -> Bf end
> where E is such that both forms are syntactically legal.
> It *looks* as though the choice is purely stylistic.
> So it should *be* purely stylistic, otherwise it would
> be gratuitously difficult to change from one to the other.
> And that means that
> 	cond foobar -> Bt ; true -> Bf end
> should execute Bf and NOT complain about foobar.
> (Yes, my prototype got this wrong.  I just hadn't thought
> it through clearly.)

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