Answer by Lewis Kelsey for What is Weak Head Normal Form?
Head normal form means there is no head redex(λx.((λy.y+x)b))bReduces to: R, for redex (and yes there's another redex inside it but this is irrelevant). This is a head redex because it's the leftmost...
View ArticleAnswer by Couchy for What is Weak Head Normal Form?
I realize this is an old question, but here is an explicit mathematical definition of WHNF, HNF, and NF. In the pure lambda calculus:A term is in NF if it is of the formλ x1. λ x2. ... λ xn. (x t1 t2...
View ArticleAnswer by Tomek Dobrzynski for What is Weak Head Normal Form?
In an implementation of graph reduction, lazy evaluation to HNF forces you to deal with the name capture problem of lambda calculus, whereas lazy evaluation to WHNF lets you avoid it.This is explained...
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Answer by aculich for What is Weak Head Normal Form?
The section on Thunks and Weak Head Normal Form in the Haskell Wikibooks description of laziness provides a very good description of WHNF along with this helpful depiction:Evaluating the value (4, [1,...
View ArticleAnswer by hammar for What is Weak Head Normal Form?
I'll try to give an explanation in simple terms. As others have pointed out, head normal form does not apply to Haskell, so I will not consider it here.Normal formAn expression in normal form is fully...
View ArticleAnswer by Heinrich Apfelmus for What is Weak Head Normal Form?
Haskell programs are expressions and they are run by performing evaluation.To evaluate an expression, replace all function applications by their definitions. The order in which you do this does not...
View ArticleAnswer by marc for What is Weak Head Normal Form?
The WHNF does not want the body of lambdas to be evaluated, soWHNF = \a -> thunkHNF = \a -> a + cseq wants its first argument to be in WHNF, solet a = \b c d e -> (\f -> b + c + d + e + f)...
View ArticleAnswer by Chris Smith for What is Weak Head Normal Form?
A good explanation with examples is given at http://foldoc.org/Weak+Head+Normal+Form Head normal form simplifies even the bits of an expression inside of a function abstraction, while "weak" head...
View ArticleAnswer by alternative for What is Weak Head Normal Form?
Basically, suppose you have some sort of thunk, t.Now, if we want to evaluate t to WHNF or NHF, which are the same except for functions, we would find that we get something liket1 : t2 where t1 and t2...
View ArticleWhat is Weak Head Normal Form?
What does Weak Head Normal Form (WHNF) mean? What does Head Normal form (HNF) and Normal Form (NF) mean?Real World Haskell states:The familiar seq function evaluates an expression to what wecall head...
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