The Metacircular Evaluator $($Racket Language$)$

Add support for and and or to your interpreter by modifying mceval. rkt$.$ Be sure your implementation adheres to the R$5$RS standard. Pay careful

attention to how the arguments to and and or are evaluated and the value of the and or or expression$-$the language standard describes a recursive

procedure for evaluating and and or expressions. Also make sure you evaluate each subexpression at most once.

You will probably want to use the last$-$exp?, first$-$exp, and rest$-$exps helper functions.

Hint: Before you start, think carefully about whether or not and and or must be implemented as special forms. When must a new language construct

be a special form?

$($define $($self$-$evaluating? exp$)$

$($cond $(($number$?$ exp$)$ true$)$

$(($string$?$ exp$)$ true$)$

$(($char$?$ exp$)$ true$)$

$(($boolean$?$ exp$)$ true$)$

$($else false$)))$

$($define $($quoted$?$ exp$)$

$($tagged$-$list? exp 'quote$))$

$($define $($text$-$of$-$quotation exp$)($cadr exp$))$

$($define $($tagged$-$list? exp tag$)$

$($if $($pair$?$ exp$)$

$($eq$?($car exp$)$ tag$)$

false$))$

$($define $($variable$?$ exp$)($symbol$?$ exp$))$

$($define $($assignment$?$ exp$)$

$($tagged$-$list? exp 'set!$))$

$($define $($assignment$-$variable exp$)($cadr exp$))$

$($define $($assignment$-$value exp$)($caddr exp$))$

$($define $($definition$?$ exp$)$

$($tagged$-$list? exp 'define$))$

$($define $($definition$-$variable exp$)$

$($if $($symbol$?($cadr exp$))$

$($cadr exp$)$

$($caadr exp$)))$

$($define $($definition$-$value exp$)$

$($if $($symbol$?($cadr exp$))$

$($caddr exp$)$

$($make$-$lambda $($cdadr exp$)$

$($cddr exp$))))$

$($define $($lambda$?$ exp$)($tagged$-$list? exp 'lambda$))$

$($define $($lambda$-$parameters exp$)($cadr exp$))$

$($define $($lambda$-$body exp$)($cddr exp$))$

$($define $($make$-$lambda parameters body$)$

$($cons 'lambda $($cons parameters body$)))$

$($define $($if$?$ exp$)($tagged$-$list? exp $\text{'}$if$))$

$($define $($if$-$predicate exp$)($cadr exp$))$

$($define $($if$-$consequent exp$)($caddr exp$))$

$($define $($if$-$alternative exp$)$

$($if $($not $($null$?($cdddr exp$)))$

$($cadddr exp$)$

'false$))$

$($define $($make$-$if predicate consequent alternative$)$

$($list $\text{'}$if predicate consequent alternative$))$

$($define $($begin$?$ exp$)($tagged$-$list? exp 'begin$))$

$($define $($begin$-$actions exp$)($cdr exp$))$

$($define $($last$-$exp? seq$)($null$?($cdr seq$)))$

$($define $($first$-$exp seq$)($car seq$))$

$($define $($rest$-$exps seq$)($cdr seq$))$

$($define $($sequence$->$exp seq$)$

$($cond $(($null$?$ seq$)$ seq$)$

$(($last$-$exp? seq$)($first$-$exp seq$))$

$($else $($make$-$begin seq$))))$

$($define $($make$-$begin seq$)($cons 'begin seq$))$

$($define $($application$?$ exp$)($pair$?$ exp$))$

$($define $($operator exp$)($car exp$))$

$($define $($operands exp$)($cdr exp$))$

$($define $($no$-$operands? ops$)($null$?$ ops$))$

$($define $($first$-$operand ops$)($car ops$))$

$($define $($rest$-$operands ops$)($cdr ops$))$

$($define $($cond$?$ exp$)($tagged$-$list? exp 'cond$))$

$($define $($cond$-$clauses exp$)($cdr exp$))$

$($define $($cond$-$else$-$clause? clause$)$

$($eq$?($cond$-$predicate clause$)$ 'else$))$

$($define $($cond$-$predicate clause$)($car clause$))$

$($define $($cond$-$actions clause$)($cdr clause$))$

$($define $($cond$->$if exp$)$

$($expand$-$clauses $($cond$-$clauses exp$)))$

$($define $($expand$-$clauses clauses$)$

$($if $($null$?$ clauses$)$

'false ; no else clause

$($let $(($first $($car clauses$))$

$($rest $($cdr clauses$)))$

$($if $($cond$-$else$-$clause? first$)$

$($if $($null$?$ rest$)$

$($sequence$->$exp $($cond$-$actions first$))$

$($error "ELSE clause isn't last $--$ COND$->$IF$"$

clauses$))$

$($make$-$if $($cond$-$predicate first$)$

$($sequence$->$exp $($cond$-$actions first$))$

$($expand$-$clauses rest$))))))$