Consider the following context free grammar for an arithmetic expression contain- ing operation - only -> number -> - number €

(a) The following is an attribute grammar to define the value of any arithmetic expres- sion specified by the grammar above.

-> number D. value := .value > .st := number. value -> - number > 2.st := 1.st - number. value > 1.value : = 2.value -> > .value := .st Draw a decorated parse tree for 1-2-3-4 using the attribute grammar.

(b) Instead of the value of an arithmetic expression, we would like to know the number of "numbers" in an arithmetic expression. For example, in 1-2-3-4, we have four numbers. Write an attribute grammar to define the number of "numbers" of any arithmetic expression following the grammar in part a).