Y Videos for CS 3520/6520

• Y 1 — introduction (2:57)

  Goal: use let and lambda to encode a recursive letrec expression.

• Y 2 — self-application (1:58)

  Our first step in understanding the letrec encoding is to implement the factorial function in Shplait without letrec.

• Y 3 — isolate function body (2:26)

  Our second step in understanding the letrec encoding is to separate the part of the factorial function’s implementation that is not specific to the factorial function.

• Y 4 — parsing letrec (1:18)

  Our third and final step in understanding the letrec encoding is to identify the equivalent expression that parse can produce for an input letrec form.

• Y 5 — Y combinator (1:39)

  The key part of our encoding, mk-rec is a fixed-point combinator. The famous Y combinator is another.