CODEWITHSUNDEEP
listfunctionerlanglist-comprehension
nedwed
nedwed

Reputation: 243

Erlang- Encoding function in my list comprehension doesn't seem to work?

%% Function even_print(List),takes a list and returns a list of only even numbers. Function even_odd(X), takes an integer and tells if it is even or odd. 

 even_print(List) ->
           [X||X<-List, even<-even_odd(X)].

I don't understand why I get this error:

3> seq_erlang:even_print([2,3,4]).              
** exception error: no function clause matching 
                    seq_erlang:'-even_print2/1-lc$^1/1-1-'(even) (seq_erlang.erl, line 154)

Just to comment, I have already implemented another function that prints even numbers just fine (so please don't comment with other implementations). I need help with this one only.

Upvotes: 2

Views: 113

Answers (1)

legoscia
legoscia

Reputation: 41528

That should be even == even_odd(X) instead of using <-. A list comprehension has two types of "clauses": those that map over a list with <-, and those that filter out undesired combinations using a guard or boolean expression that doesn't contain <-.

(And a third one: extract bytes from a binary using <=; but that one is more rarely used.)

Upvotes: 2

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