
expr --> term, "+", expr.
expr --> term, "-", expr.
expr --> term.

term --> number, "*", term.
term --> number, "/", term.
term --> number.

number --> "+", number.
number --> "-", number.
number --> [C], {"0" =< C, C =< "9"}.

/*
| ?-  expr("-2+3*5+1",[]).

yes
| ?- expr("-2+3*5+11",[]).

no
| ?-  expr("-2+3*5+11","+11").


*/
