X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=blobdiff_plain;f=hints%2Fassignment_4_hint_2.mdwn;h=f9f4cf253a0b938b2d8a877bad7d90dd7051086e;hp=78cb1bd41f1318724f9168f207868a7eb7914f84;hb=0683b3c8a32fabb9b78d9827ac809df3a6095434;hpb=3d89c06687f5fde9730a16b04c0ae0a241dcf5cb diff --git a/hints/assignment_4_hint_2.mdwn b/hints/assignment_4_hint_2.mdwn index 78cb1bd4..f9f4cf25 100644 --- a/hints/assignment_4_hint_2.mdwn +++ b/hints/assignment_4_hint_2.mdwn @@ -1,4 +1,18 @@ -Hints for list\_equal. +Hints for `list_equal`. + +* If `left` is `[]`, what does `right` have to be for `left` and `right` to be equal? (Come on, it's not too hard, you can figure it out.) + +* Suppose on the other hand that `left` has head `left_hd` and tail `left_tl`. + +
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  1. If `right` is then `[]`, are `left` and `right` equal? +
  2. If `right` isn't `[]`, and its head isn't equal to `left_hd`, are `left` and `right` equal? +
  3. If `right` isn't `[]` and its head *is* equal to `left_hd`, what else has to be the case for `left` and `right` to be equal? +
+ +* Can you now write a recursive definition of the `list_equal` function? +What's your base case? + + + +