![]() ![]() It also helps impose referential transparency. ![]() this helps prevent cheating and defining recursive functions. All definitions in the language are immutible. Once something is defined, it cannot be changed. This is called lazy evaluation or normal order evaluation, as opposed to eager or applicative order evaluation. We write a rather small lambda calculus expression parser, evaluator, and repl in Haskell. The last line returns true because Lambda Light substitutes a variable for it's relevant binding only when it is being called, instead of when it is an argument to a function. Λ: not := \b.b false true - Lambda Light allows you to create functions with named functions. Λ: false := \x.\y.y - Lambda Light supports bindings to a global namespace. In this homework you will write a normal order interpreter that yields an answer in Normal Form (i.e., the expression cannot be further reduced). ![]() They terminated when they reached an answer in Weak Head Normal Form. Λ: true := \x.\y.x - Lambda Light supports binding names to expressions. In lecture, we wrote several interpreters for the Lambda Calculus. Thus our interpreter actually runs more than plain lambda. Notes Num is distinct from the standard type class Num. The only kinds of Values are Numbers, Functions, and Errors. The interpeter evaluates an Expression with respect to an Environment, which is a list of bindings of Names to Values. Λ: (λx.x x) (λx.x) - Lambda Light supports function application. These on-demand lookups and the way we update env means recursive let definitions are possible. Haskell familiarization Here is a basic lambda calculus interpreter written in Haskell. Λ: \x.x - Lambda Light supports the creation lambda expressions using \ and the unicode λ character. Contents 1 Large languages 1.1 Haskell 1.1.1 Helium 1.1. Here's a selection of compilers and interpreters implemented in Haskell. This leads to: > data Dinf NoBeta NoBeta > Fn. Haskell, with its support for pattern matching on data structures, generic structure traversals, and expressive type system, is popular for implementing compilers and interpreters. Λ: x - Lambda Light supports creating arbitrary variables. Remember that a normal form is a lambda term with no beta redexes. Λ: - Lambda Light supports Haskell-like single line comments ![]()
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