Mead

It is a tiny parse transform.

License: MIT

Author: Uvarov Michael ([email protected])

-compile({parse_transform, mead}).

Example 1

From lists (Erlang/OTP).

Before:

usplit_1(X, Y, [Z | L], R, Rs) when Z > Y ->
    usplit_1(Y, Z, L, [X | R], Rs);
usplit_1(X, Y, [Z | L], R, Rs) when Z == Y ->
    usplit_1(X, Y, L, R, Rs);
usplit_1(X, Y, [Z | L], R, Rs) when Z > X ->
    usplit_1(Z, Y, L, [X | R], Rs);
usplit_1(X, Y, [Z | L], R, Rs) when Z == X ->
    usplit_1(X, Y, L, R, Rs);
usplit_1(X, Y, [Z | L], [], Rs) ->
    usplit_1(X, Y, L, [Z], Rs);
usplit_1(X, Y, [Z | L], R, Rs) ->
    usplit_1_1(X, Y, L, R, Rs, Z);
usplit_1(X, Y, [], R, Rs) ->
    rumergel([[Y, X | R] | Rs], [], asc).

After:

usplit_1(X, Y, [Z | L], R, _) when Z > Y  -> me(Y, Z, L, [X | R], _);
usplit_1(_, Y, [Z | L], _, _) when Z == Y -> me(_, Y, L, _, _);
usplit_1(X, _, [Z | L], R, _) when Z > X  -> me(Z, _, L, [X | R], Rs);
usplit_1(X, _, [Z | L], _, _) when Z == X -> me(X, _, L, _, _);
usplit_1(_, _, [Z | L], [], _)            -> me(_, _, L, [Z], _);
usplit_1(X, Y, [Z | L], R, Rs) ->
    usplit_1_1(X, Y, L, R, Rs, Z);
usplit_1(X, Y, [], R, Rs) ->
    rumergel([[Y, X | R] | Rs], [], asc).

Example 2

From cyrsasl_digest (ejabberd).

Before:

parse1([$= | Cs], S, Ts) ->
    parse2(Cs, lists:reverse(S), "", Ts);
parse1([$, | Cs], [], Ts) ->
    parse1(Cs, [], Ts);
parse1([$\s | Cs], [], Ts) ->
    parse1(Cs, [], Ts);
parse1([C | Cs], S, Ts) ->
    parse1(Cs, [C | S], Ts);
parse1([], [], T) ->
    lists:reverse(T);
parse1([], _S, _T) ->
    bad.

After:

parse1([$= | Cs], S, Ts)   -> parse2(Cs, lists:reverse(S), "", Ts);
parse1([$, | Cs], [], _)   -> me(Cs, _, _);
parse1([$\s | Cs], [], _)  -> me(Cs, _, _);
parse1([C | Cs], S, _)     -> me(Cs, [C | S], _);
parse1([], [], T)          -> lists:reverse(T);
parse1([], _S, _T)         -> bad.

Arguments

This parse transform adds the hidden arguments.

Source code:

map(X, [H|T]) ->
    [F(H)|map(X, T)];
map(F, []) ->
    [].

Code after this parse transform:

map(_1 = X, _2 = [H|T]) ->
    [F(H)|map(X, T)];
map(_1 = F, _2 = []) ->
    [].

Other functions

• fun_me() - returns the current function as a HOF (fun F/A);
• my_arguments() - returns arguments as a list;
• my_name() - returns the name of the current function;
• my_arity() - returns the count of arguments of the current function.

Examples

These functions can be used for formatting debug messages.

response(KeyVals, User, Passwd, Nonce, AuthzId, A2Prefix) ->
    %% debug
    error_logger:info_msg("[~s~s] Args: ~w~n",
        [?MODULE, my_name(), my_arguments()]),
    ...