Question: Consider expressions built up from natural numbers using a subtraction operator that is assumed to associate to the left. (a) Define a natural grammar for

Consider expressions built up from natural numbers using a subtraction operator that is assumed to associate to the left.

(a) Define a natural grammar for such expressions.

(b) Translate this grammar into a parser expr: Parser Int.

(c) What is the problem with this parser?

(d) Show how it can be fixed. Hint: rewrite the parser using the repetition primitive many and the library function foldl.

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