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.CENT(Problems involving %3prog%*)
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I. Write %3prog%*-versions of the following functions (or predicates).

%21.%3 member <= λ[[x;y] ...]%1:%3 x%1 is atomic; %3y%* is a list of atoms.  %3member%* is to 
return %et%* just in the case that %3x%* is one of the elements in %3y%*.

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.APART
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%22.%1 The factorial function.

%23.%3  delete <= λ[[x;y] ... ]%1: %3x%1 is atomic; %3y%* is a list of atoms.  %3delete%* is to 
return a list which looks like %3y%*, except all occurrences of %3x%*
have been deleted.

%24.%1 The %3append%* function.
.APART
.GROUP;

%25.%3  last <= λ[[x] ...]%1: %3x%1 is a non-empty list.  %3last%* is to return the last 
element in %3x%*.

%26.%1  Now write the S-expr translations of each of your functions.


II. What is necessary to extend  the evaluator to recognize %3prog%* and friends?

.END
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III. The %3go[cdr[...]]%*-construct on {yon(P25)} is better handled with a %2⊗→case 
statement↔←%*. A typical syntax for such might be:
.P70:

←case<index>of <form%41%*>; ... ;<form%4n%*>.

<index> is to evaluate to an integer, i. Where  0<i≤n. The i%8th%* <form> of the
case-statement is executed, and is the value of the statement.
Give a representation for the case statement and extend the evaluator to recognize
it.
.apart

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IV. Some languages allow
constructs like:

.BEGIN TURN OFF "←";CENTER;
(%2if%* p(x) %2then%* x %2else%* y) ← exp, which is to mean the same as:

%2if%* p(x) %2then%* x← exp %2else%* y ← exp
.END
Can such a construct be written in LISP?
.apart

V. Compare the %3prog%* version of %3length%* on {yon(P45)} with 
%3length%41%1 on {yon(P19)}. Do you see any interesting relationships? 
.END