Erlang How can I merge Two list into tuple list

Question

In erlang, I want to merge two list as the following

when, A = [1, 2, 3, 4], B= ["A1", "A2", "A3", A4],

wanted result [{1, "A1"}, {2, "A2"}, {3, "A3"}, {4, A4}]

I've tried the following

''' - module(test). - export([start/0]).

    start() ->
        Abc = [2,3,1,4],
        Bbc=["f1", "f2", "f3",f4],
        ct:pal("Hello ~n"),
        ct:pal("make_tuple_list ~p~n", [make_tuple_list(Abc,Bbc)]).

    make_tuple_list([H1 | T1], [H2 | T2]) ->
        [_ | _] = [{H1, H2} | make_tuple_list(T1, T2)].

    make_tuple_list([], []) -> [].

''' but got the systax erorr as the following

test.erl:14: function make_tuple_list/2 already defined

thanks in advance.

Answer 1

Try following....

-module(test).
-export([start/0]).

start() ->
    Abc = [2,3,1,4],
    Bbc=["f1", "f2", "f3",f4],
    ct:pal("Hello ~n"),
    ct:pal("make_tuple_list ~p~n", [make_tuple_list(Abc,Bbc)]).

make_tuple_list([H1 | T1], [H2 | T2]) ->
    [{H1, H2} | make_tuple_list(T1, T2)];

make_tuple_list([], []) -> [].

Separator for splitting function clauses is ;. . is function definition terminator. In the above case, both occurrences of make_tuple_list are ending with ., which essentially means, in the second occurrence we are re-defining an already defined function, which is not allowed in ErLang.

Answer 2

-module(lc).
-export([start/0]).

start() ->
    Columns = ["id", "firstname", "lastname", "prefix", "initials", "birthday"],
    Rows = [
                [82, "Bob", "Dubalina", "", "B.", {1971,1,29}],
                [45, "Alice", "Wonderland", "", "A.", {1975,2,14}],
                [23, "John", "Doe", "", "J.", {1982,5,5}],
                [72, "Jane", "Doe", "", "J.", {1995,7,17}]
            ],
    Data = #{ "data" =>    [ 
                            maps:from_list([ {lists:nth(X, Columns) , lists:nth(X, Values)} || X <- lists:seq(1, length(Columns))])
                        || Values <- Rows ] 
            },
    Data.