COMMENT ⊗   VALID 00002 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	.BEGIN "prob3" CENTERITTABIT2(13,28)SELECT 1
C00004 ENDMK
C⊗;
.BEGIN "prob3" CENTERIT;TABIT2(13,28);SELECT 1;

.GROUP;

2.##Consider the following definition:
.pt18;
%3
\  twist[s] <=\[atom[s] → s;
\\ %et%* → cons[twist[cdr[s]];twist[car[s]]]]
.pt18;
%2a%1. Is the function partial or is it total? Now evaluate: 
.pt2
%2b.%3 twist[A]   %2c.%3 twist[(A . B)]   %2d.%3 twist[((A . B) . C)]
.APART
.END "PROB3"
.BEGIN "PROB3A" CENTERIT;TABIT2(10,25);SELECT 1;
.GROUP
.pt18;
%1
3.##Now try:
.pt18;
%3
\findem[x;y] <=\[atom[x] → [eq[x;y] → T; %et%* → NIL];
\\ %et%* → cons[findem[car[x];y];findem[cdr[x];y]]]
.pt18;
%2a%1.  Is this function total? Now evaluate:
.pt2
←%2b.%3 findem[(A . B);A]   %2c.%3 findem[(B .(A . C));A]  
.pt2
←%2d.%3 findem[(B .(A . C));C]  %2e.%3 findem[(A . B);(A . B)]
.APART

.END "prob3A"