Increase list size using list comprehension in erlang

Question

A = [1,2,3]

The output should be:

[1,one,2,two,3,three]

Is it possible to get such an output?

You can use the process described here https://stackoverflow.com/questions/1684431/how-to-convert-numbers-to-words-in-erlang — Roman Rabinovich, Sep 21 '18 at 00:16

score 5 · Accepted Answer · answered Sep 20 '18 at 19:38

5

Yes, you can put two clauses in the comprehension and make the second one return two elements for each element in the first one:

1> F = fun
1>   (1) -> "one";
1>   (2) -> "two";
1>   (3) -> "three"
1> end.
#Fun<erl_eval.6.127694169>
2> [B || A <- [1, 2, 3], B <- [A, F(A)]].
[1,"one",2,"two",3,"three"]

answered Sep 20 '18 at 19:38

Dogbert

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Thanks a lot !! So there needs to be some sort of mapping or use of a user-defined function to make this work right? – Abhay Sep 20 '18 at 19:45
@Abhay, Of course! The atom `three` has no inherent relationship to the integer `3`. – 7stud Sep 21 '18 at 04:32

score 0 · Answer 2 · answered Oct 01 '18 at 07:37

i think the out put of last code would be

 [[1 ,"one"] , [2, "two"] , [3 , "tree"]].

some right answer will be

  lists:append([begin T = case I of
                            1 -> "One" ;
                            2->"Two";
                            3->"Three"; 
                            _ -> "" end ,
                      [I ,T] end
               || I <- lists:seq(1,3)]).

Increase list size using list comprehension in erlang

2 Answers2