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

test() ->
	{1, "a"} = map_guard_sequence_1(#{seq=>1,val=>id("a")}),
	{2, "b"} = map_guard_sequence_1(#{seq=>2,val=>id("b")}),
	{3, "c"} = map_guard_sequence_1(#{seq=>3,val=>id("c")}),
	{4, "d"} = map_guard_sequence_1(#{seq=>4,val=>id("d")}),
	{5, "e"} = map_guard_sequence_1(#{seq=>5,val=>id("e")}),

	{1,M1}       = map_guard_sequence_2(M1 = id(#{a=>3})),
	{2,M2}       = map_guard_sequence_2(M2 = id(#{a=>4, b=>4})),
	{3,gg,M3}    = map_guard_sequence_2(M3 = id(#{a=>gg, b=>4})),
	{4,sc,sc,M4} = map_guard_sequence_2(M4 = id(#{a=>sc, b=>3, c=>sc2})),
	{5,kk,kk,M5} = map_guard_sequence_2(M5 = id(#{a=>kk, b=>other, c=>sc2})),

	%% error case
	{'EXIT',{function_clause,_}} = (catch map_guard_sequence_1(#{seq=>6,val=>id("e")})),
	{'EXIT',{function_clause,_}} = (catch map_guard_sequence_2(#{b=>5})),
	ok.

map_guard_sequence_1(#{seq:=1=Seq, val:=Val}) -> {Seq,Val};
map_guard_sequence_1(#{seq:=2=Seq, val:=Val}) -> {Seq,Val};
map_guard_sequence_1(#{seq:=3=Seq, val:=Val}) -> {Seq,Val};
map_guard_sequence_1(#{seq:=4=Seq, val:=Val}) -> {Seq,Val};
map_guard_sequence_1(#{seq:=5=Seq, val:=Val}) -> {Seq,Val}.

map_guard_sequence_2(#{ a:=3 }=M) -> {1, M};
map_guard_sequence_2(#{ a:=4 }=M) -> {2, M};
map_guard_sequence_2(#{ a:=X, a:=X, b:=4 }=M) -> {3,X,M};
map_guard_sequence_2(#{ a:=X, a:=Y, b:=3 }=M) when X =:= Y -> {4,X,Y,M};
map_guard_sequence_2(#{ a:=X, a:=Y }=M) when X =:= Y -> {5,X,Y,M}.

%% Use this function to avoid compile-time evaluation of an expression.
id(I) -> I.