term: factor | term `*' factor | term `/' factor
factor: primary | `+' factor | `-' factor
primary: int | id | string | `(' expression `)' | `{' fragment `}'
term: factor | term `*' factor | term `/' factor
factor: primary | `+' factor | `-' factor
primary: int | id | string | `(' expression `)' | `{' fragment `}'