[erlang-questions] Matching Empty maps

Björn-Egil Dahlberg XB <>
Tue Feb 7 16:25:23 CET 2017


On 02/07/2017 12:45 PM, Joe Armstrong wrote:
> So #{} is an empty map in an argument position but not an empty map
> in a pattern.
Yes, of course!

There is a difference between patterns and values. They are not the same 
thing.

A pattern does not need to describe the entire thing in match. It just 
has to describe the things it needs to match.

Records are the precursor to the map behavior of course. For example,

-record(r, {a,b,c}).

foo(#r{}=R) ->
     R.

// Björn-Egil



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