Question

Consider expressions built up from natural numbers using a subtraction operator that is assumed to associate to the left. a. Translate this description directly into a grammar. b. Implement this grammar as 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.

   Consider expressions built up from natural numbers using a subtraction operator that is assumed to associate to the left.
a. Translate this description directly into a grammar.
b. Implement this grammar as 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.

Show more…

Programming in Haskell

Programming in Haskell

Graham Hutton 2nd Edition

Chapter 13, Problem 8

Instant Answer

Step 1

The grammar for expressions built up from natural numbers using a subtraction operator that associates to the left can be written as: expr -> term | expr "-" term term -> factor | term "-" factor factor -> number | "(" expr ")" number -> "0" | "1" | "2" | ... b. Show more…

Show all steps

lock

Thanks for your feedback!

Consider expressions built up from natural numbers using a subtraction operator that is assumed to associate to the left. a. Translate this description directly into a grammar. b. Implement this grammar as 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.

Play audio

Feedback

Powered by NumerAI

Ace is your personal tutor. It breaks down any question with clear steps so you can learn.

Start Using Ace

Continue solving this problem

Create a free account to:

View full step-by-step solution
Ask follow-up questions with Ace AI
Save progress and study later