helpers.tex

\chapter{Familiar Helpers}\label{helpers}
The auxiliaries below are used in the implementation of \alphakanrensp in Chapter~\ref{akimplchapter}.

\schemedisplayspace
\begin{schemedisplay}
(define get
  (lambda (x s)
    (cond
      ((assq x s) => cdr)
      (else x))))

(define assp
  (lambda (p s)
    (cond
      ((null? s) #f)
      ((p (car (car s))) (car s))
      (else (assp p (cdr s))))))
\end{schemedisplay}

\begin{schemedisplay}
(define filter
  (lambda (p s)
    (cond
      ((null? s) '())
      ((p (car s)) (cons (car s) (filter p (cdr s))))
      (else (filter p (cdr s))))))

(define remove-duplicates
  (lambda (s)
    (cond
      ((null? s) '())
      ((memq (car s) (cdr s)) (remove-duplicates (cdr s)))
      (else (cons (car s) (remove-duplicates (cdr s)))))))
\end{schemedisplay}