X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=week1.mdwn;h=36ebdfcc6a48bf72288e2023a0186b9c6665de2d;hp=e8154e3cdcf1fbe6c21828c266662113bc7f9971;hb=00b6e7be50487a25a1d96ec239f04271f0be53a6;hpb=1f97960ab1bdd7a1328fe64714e8b36b38bd7a1e diff --git a/week1.mdwn b/week1.mdwn index e8154e3c..36ebdfcc 100644 --- a/week1.mdwn +++ b/week1.mdwn @@ -57,7 +57,7 @@ We'll tend to write (λa M) as just `(\a M)`, so we don't hav Application: (M N) -Some authors reserve the term "term" for just variables and abstracts. We won't participate in that convention; we'll probably just say "term" and "expression" indiscriminately for expressions of any of these three forms. +Some authors reserve the term "term" for just variables and abstracts. We'll probably just say "term" and "expression" indiscriminately for expressions of any of these three forms. Examples of expressions: @@ -70,9 +70,11 @@ Examples of expressions: (x (\x x)) ((\x (x x)) (\x (x x))) -The lambda calculus has an associated proof theory. For now, we can regard the proof theory as having just one rule, called the rule of **beta-reduction** or "beta-contraction". Suppose you have some expression of the form: +The lambda calculus has an associated proof theory. For now, we can regard the +proof theory as having just one rule, called the rule of **beta-reduction** or +"beta-contraction". Suppose you have some expression of the form: - ((\a M) N) + ((\ a M) N) that is, an application of an abstract to some other expression. This compound form is called a **redex**, meaning it's a "beta-reducible expression." `(\a M)` is called the **head** of the redex; `N` is called the **argument**, and `M` is called the **body**.