X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=week4.mdwn;h=8714eae88f924c42f7ba6560530d3094be741f07;hp=e01db2e857d5550eee64aa84f99860658b2fea47;hb=f4e64dfd73d6935c7636a1f4586b7d5202a74272;hpb=72af25c790aaa979710ffc2b7fab823ffaf94b05 diff --git a/week4.mdwn b/week4.mdwn index e01db2e8..8714eae8 100644 --- a/week4.mdwn +++ b/week4.mdwn @@ -192,11 +192,10 @@ are also forbidden, so recursion is neither simple nor direct. #Types# -We will have at least one ground type, `o`. From a linguistic -point of view, thing of the ground types as the bar-level 0 -categories, the lexical types, such as Noun, Verb, Preposition -(glossing over the internal complexity of those categories in modern -theories). +We will have at least one ground type, `o`. From a linguistic point +of view, think of the ground types as the bar-level 0 categories, that +is, the lexical types, such as Noun, Verb, Preposition (glossing over +the internal complexity of those categories in modern theories). In addition, there will be a recursively-defined class of complex types `T`, the smallest set such that @@ -218,7 +217,7 @@ and so on. #Typed lambda terms# -Given a set of types `T`, we define the set of typed lambda terms `&Lamda;_T`, +Given a set of types `T`, we define the set of typed lambda terms Λ_T, which is the smallest set such that * each type `t` has an infinite set of distinct variables, {x^t}_1, @@ -228,12 +227,12 @@ which is the smallest set such that σ, then the application `(M N)` has type τ. * If a variable `a` has type σ, and term `M` has type τ, - then the abstract `λ a M` has type `σ --> τ`. + then the abstract λ a M has type σ --> τ. The definitions of types and of typed terms should be highly familiar -to semanticists, except that instead of writing `σ --> τ`, -linguists (following Montague, who followed Church) write `<σ, -τ>`. We will use the arrow notation, since it is more iconic. +to semanticists, except that instead of writing σ --> τ, +linguists (following Montague, who followed Church) write <σ, +τ>. We will use the arrow notation, since it is more iconic. Some examples (assume that `x` has type `o`):