map.xrl

Definitions.
D   = [0-9]
L   = [A-Za-z]
WS  = ([\000-\s]|%.*)
C   = (\:\-|\-\>)
WC  = [A-Za-z0-9]


Rules.
{WS}             : skip_token.
\.               : skip_token.
{WC}+            : {token, {path_symbol, TokenLine, TokenChars}}.
{C}              : {token, {path_divider, TokenLine}}.

Erlang code.

map_g.yrl

%-*- Erlang -*-
Terminals path_symbol path_divider.
Nonterminals Path Rule .
Rootsymbol Rule.

%% rules ->
%%     rule rules.
%% rules ->
%%     rule.

Rule ->
    Path path_divider Path : {map, '$1','$3'}.

Path  ->
    path_symbol Path : ['$1' | '$2'].
Path ->
    path_symbol : ['$1'].

Erlang code.

results.erl

(wm@draco)11> {ok, L, _} = map:string( "product image small string -> product image label").
{ok,[{object,1,{path_symbol,"product"}},
     {object,1,{path_symbol,"image"}},
     {object,1,{path_symbol,"small"}},
     {object,1,{path_symbol,"string"}},
     {object,1,path_divider},
     {object,1,{path_symbol,"product"}},
     {object,1,{path_symbol,"image"}},
     {object,1,{path_symbol,"label"}}],
    1}
(wm@draco)12> map_g:parse(L).
{error,{1,map_g,
        ["syntax error before: ",
         [[123,["path_symbol",44,"\"product\""],125]]]}}