From cbefb85dba25ca424e54e84849c2a24a105e0121 Mon Sep 17 00:00:00 2001
From: Isaac Shoebottom <ir.shoebottom@gmail.com>
Date: Wed, 26 Mar 2025 16:50:55 -0300
Subject: [PATCH] Add more documentation

---
 Assignments/02.rkt | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/Assignments/02.rkt b/Assignments/02.rkt
index cf55e67..417694b 100644
--- a/Assignments/02.rkt
+++ b/Assignments/02.rkt
@@ -118,18 +118,27 @@
       [(timesE l r) (num2 l r (numT))]
       [(leqE l r) (num2 l r (boolT))]
       [(varE s) (type-lookup s env)]
+      ; todo ensure correctness?
+      ; https://www.cs.unb.ca/~bremner/teaching/cs4613/docs/plai-3.2.2.pdf#page=127
       [(lamE name te body) (arrowT (interp-te te) (typecheck body (type-extend env name (interp-te te))))]
-      [(appE fn arg) (type-case Type (typecheck fn env) ; todo use local to reduce duplicate calls
+      ; todo use local to reduce duplicate calls
+      ; https://www.cs.unb.ca/~bremner/teaching/cs4613/docs/plai-3.2.2.pdf#page=124
+      [(appE fn arg) (type-case Type (typecheck fn env) 
                          [(arrowT a b) (typecheck fn env)]
                          [else (error 'app "Function application must be a function")])]
-      [(ifE c t f) (if (equal? (typecheck c env) (boolT)) ; todo use type case/local to reduce duplicate calls`
+      ; todo use type case/local to reduce duplicate calls
+      ; https://www.cs.unb.ca/~bremner/teaching/cs4613/docs/plai-3.2.2.pdf#page=119
+      [(ifE c t f) (if (equal? (typecheck c env) (boolT))
                     (if (equal? (typecheck t env) (typecheck f env))
                        (typecheck t env)
                        (error 'if "Both if conditions must be of the same type"))
                     (error 'if "Condition must be a boolean expression"))]
+      ; https://www.cs.unb.ca/~bremner/teaching/cs4613/docs/plai-3.2.2.pdf#page=129
       [(let1E var te val body) (typecheck body (type-extend env var (interp-te te)))]
-      [(recE var te val body) (typecheck body (type-extend env var (interp-te te)))] ; figure out https://www.cs.unb.ca/~bremner/teaching/cs4613/docs/plai-3.2.2.pdf#page=132
-)))
+      ; https://www.cs.unb.ca/~bremner/teaching/cs4613/docs/plai-3.2.2.pdf#page=132
+      [(recE var te val body) (type-case Type (typecheck body (type-extend env var (interp-te te)))
+                                [(arrowT a b) b]
+                                [else (error 'rec "rec body must be a function")])])))
 
 (tc : (S-Exp -> Type))
 (define (tc s)
@@ -148,3 +157,15 @@
 (test/exn (tc `{lam {n : num} {if n 1 2}}) "boolean")
 
 (test/exn (tc `{1 1}) "function")
+
+
+; Tests added for complete coverage
+(test (tc `false) (boolT))
+(test (tc `true) (boolT))
+
+(test (tc `{- 2 1}) (numT))
+(test (tc `{* 2 2}) (numT))
+
+(test/exn (tc `{rec {[fact : (num -> num)] {lam {n : num} {if {<= n 0} 1 {* n {fact {- n 1}}}}}} false}) "function")
+
+(test/exn (tc `{lam {n : num} {if {<= n 0} 1 false}}) "same type")
\ No newline at end of file