Mathematical expression interpreter(Haskell по шаблону)

Your task is to:
1)Write monadic parsing combinators
2)Define a structure to represent a parsed mathematical expression in Haskell
3)Write a parser, which parses a string into the structure
4)Write an interpreter for the structure, which performs the calculation and returns the result.
NOTE: the parser and interpreter should be independent.
You will have to handle division by zero errors.
Более подробное описание и шаблон кода, после предварительного обсуждения
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