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@@ -4150,7 +4150,7 @@ $40$, to which we add the $2$, the element at index $0$ of the
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(\key{vector-ref}\;\Exp\;\Int) \\
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&\mid& (\key{vector-set!}\;\Exp\;\Int\;\Exp)\\
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&\mid& (\key{void}) \\
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- R_3 &::=& (\key{program} \;(\key{type}\;\itm{type})\; \Exp)
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+ R_3 &::=& (\key{program} \; \Exp)
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\end{array}
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\]
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\end{minipage}
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@@ -5254,21 +5254,20 @@ that does what its name suggests. The program then applies
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The definitional interpreter for $R_4$ is in
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Figure~\ref{fig:interp-R4}.
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-%% change to do backpatching -Jeremy
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\begin{figure}[tp]
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\begin{lstlisting}
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-(define (interp-exp env global-env)
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+(define (interp-exp env)
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(lambda (e)
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- (define recur (interp-exp env global-env))
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+ (define recur (interp-exp env))
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(match e
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...
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[`(,fun ,args ...)
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- (define fun-val (recur fun))
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(define arg-vals (map recur args))
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+ (define fun-val (recur fun))
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(match fun-val
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- [`(lambda (,xs ...) ,body)
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- (define new-env (append (map cons xs arg-vals) global-env))
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- ((interp-exp new-env global-env) body)]
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+ [`(lambda (,xs ...) ,body ,fun-env)
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+ (define new-env (append (map cons xs arg-vals) fun-env))
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+ ((interp-exp new-env) body)]
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[else (error "interp-exp, expected function, not" fun-val)])]
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[else (error 'interp-exp "unrecognized expression")]
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)))
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@@ -5276,14 +5275,19 @@ Figure~\ref{fig:interp-R4}.
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(define (interp-def d)
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(match d
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[`(define (,f [,xs : ,ps] ...) : ,rt ,body)
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- (cons f `(lambda ,xs ,body))]
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+ (mcons f `(lambda ,xs ,body ()))]
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))
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(define (interp-R4 p)
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(match p
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[`(program ,ds ... ,body)
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(let ([top-level (map interp-def ds)])
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- ((interp-exp top-level top-level) body))]
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+ (for/list ([b top-level])
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+ (set-mcdr! b
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+ (match (mcdr b)
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+ [`(lambda ,xs ,body ())
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+ `(lambda ,xs ,body ,top-level)])))
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+ ((interp-exp top-level) body))]
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))
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\end{lstlisting}
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\caption{Interpreter for the $R_4$ language.}
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Jeremy Siek