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Nonterminals
root
statement
statements
expr
exprs
.
Terminals
int
var
break
'+' '-' '*' '/' '!' '^'
'='
'(' ')'
.
Rootsymbol
root
.
Right 100 '='.
Left 300 '+'.
Left 300 '-'.
Left 400 '*'.
Left 400 '/'.
Right 500 '!'.
Left 600 '^'.
Left 700 '('.
root -> statements : '$1'.
statements -> statement : ['$1'].
statements -> statement statements : ['$1'|'$2'].
statements -> statement break statements : ['$1'|'$3'].
statements -> break : [].
statement -> var '=' exprs : {assign, '$1', '$3'}.
statement -> exprs : {eval, '$1'}.
exprs -> expr : '$1'.
exprs -> expr exprs : {mul_op, '$1', '$2'}.
expr -> int : unwrap('$1').
expr -> var : '$1'.
expr -> exprs '+' exprs : {add_op, '$1', '$3'}.
expr -> exprs '-' exprs : {sub_op, '$1', '$3'}.
expr -> exprs '*' exprs : {mul_op, '$1', '$3'}.
expr -> exprs '/' exprs : {div_op, '$1', '$3'}.
expr -> expr '!' : {factor_op, '$1'}.
expr -> exprs '^' exprs : {exp_op, '$1', '$3'}.
expr -> '(' exprs ')' : '$2'.
expr -> '-' exprs : {sub_op, {int, 0, 0}, '$2'}.
Erlang code.
unwrap({int, Line, Value}) ->
Match = fun(X) -> not(X == 95) end,
{int, Line, list_to_integer(lists:filter(Match, Value))}.
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