Write You a Haskell Stephen Diehl

infixl 6 +
infixl 7 *
f = 1 + 2 * 3
Renamer
After parsing we will traverse the entire AST and rename all user-named variables to machine generated
names and eliminate any name-shadowing. For example in the following ambiguous binder will replace
the duplicate occurrence of x with a fresh name.
f x y = \g x -> x + y
f x y = \g a0 -> a0 + y
-- x in definition of g shadows x in f
We will also devise a general method of generating fresh names for each pass such that the names generated
are uniquely identifiable to that pass and cannot conflict with later passes.
Ensuring that all names are unique in the syntax tree will allow us more safety later on during program
transformation, to know that names cannot implicitly capture and the program can be transformed
without changing its meaning.
Datatypes
User defined data declarations need to be handled and added to the typing context so that their use
throughout the program logic can be typechecked. is will also lead us into the construction of a
simple kind inference system, and the support of higher-kinded types.
data Bool = False | True
data Maybe a = Nothing | Just a
data T1 f a = T1 (f a)
Each constructor definition will also introduce several constructor functions into the Core representation
of the module. Record types will also be supported and will expand out into selectors for each of the
various fields.
Desugaring
Pattern matching is an extremely important part of a modern functional programming, but the implementation
of the pattern desugaring is remarkably subtle. e frontend syntax allows the expression of
nested pattern matches and incomplete patterns, both can generate very complex splitting trees of case
expressions that need to be expanded out recursively. We will use the algorithm devised Phil Wadler to
perform this transformation.
Multiple Equations
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