Comments on: Erlang Programming Exercise: 3-7 http://benjaminhalsted.com/2010/03/erlang-programming-exercise-3-7/ // [bgh] todo, add something clever here. Wed, 09 Mar 2011 02:11:50 +0000 hourly 1 http://wordpress.org/?v=3.1 By: halzy http://benjaminhalsted.com/2010/03/erlang-programming-exercise-3-7/comment-page-1/#comment-601 halzy Wed, 09 Mar 2011 02:11:50 +0000 http://benjaminhalsted.com/?p=142#comment-601 I haven't made it far enough in the book to use the list comprehension. I saw it when reading through the other book, but wanted to keep with what had been taught so far in this book. I haven’t made it far enough in the book to use the list comprehension. I saw it when reading through the other book, but wanted to keep with what had been taught so far in this book.

]]> By: Andy http://benjaminhalsted.com/2010/03/erlang-programming-exercise-3-7/comment-page-1/#comment-531 Andy Tue, 14 Sep 2010 21:02:24 +0000 http://benjaminhalsted.com/?p=142#comment-531 "case" in match/2 can be omitted: match(Element, Db) -> lists:filter(fun({_, E}) -> E =:= Element end, Db). but original exercise required that match/2 returns list of keys, not list of tuples, so it could look like: match(Element, Db) -> MatchedTuples = lists:filter(fun({_, E}) -> E =:= Element end, Db), element(1, lists:unzip(MatchedTuples)). But this is rather too complicated. Using list comprehension gives us a simpler version: match(Element, Db) -> [Key || {Key, E} <- Db, E =:= Element]. “case” in match/2 can be omitted:

match(Element, Db) ->
lists:filter(fun({_, E}) -> E =:= Element end, Db).

but original exercise required that match/2 returns list of keys, not list of tuples, so it could look like:

match(Element, Db) ->
MatchedTuples = lists:filter(fun({_, E}) -> E =:= Element end, Db),
element(1, lists:unzip(MatchedTuples)).

But this is rather too complicated. Using list comprehension gives us a simpler version:

match(Element, Db) ->
[Key || {Key, E} <- Db, E =:= Element].

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