[erlang-questions] pattern match test operator

Andras Georgy Bekes <>
Tue Dec 4 21:24:08 CET 2007

> Parse transforms happen at compilation time. What is your reasoning 
> behind "slower than a compiled implementation"?
I just think the compiler might generate more efficient code if it 
_knows_ that it is doing only a pattern match and nothing else. The 
code I've written also contains calls to erlang:error/1. OK it is a 
BIF, but still, I think a match failure is just faster than calling 
erlang:error (and building up its argument).

But, the point is not this. The point is that a parse-transform 
implementation of the stuff is almost useless, because it cannot be 
used in function heads and case and receive expressions.


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