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\documentstyle{article}
% $Id: reader.sw,v 2.0 1994/02/25 14:03:14 ramsdell Exp $
\title{{\tt read-sw}}
\author{John D. Ramsdell}
\date{\verb$Date: 1994/02/25 14:03:14 $}
\newcommand{\schemeweb}{Scheme{\tt WEB}}
\begin{document}
\maketitle
\verb|read-sw| reads a {\schemeweb} source file
much as \verb|read| reads a Scheme source file.
(define (read-sw . rest) ; Returns what \verb|read| returns.
(let ((port (if (pair? rest) ; \verb|read-sw| arguments are
(car rest) ; the same as \verb|read|'s.
(current-input-port))))
(letrec
((text-mode-and-saw-newline ; Lines of a {\schemeweb} file
(lambda () ; beginning with ``{\tt(}'',
(let ((ch (peek-char port))) ; start a code section.
(cond ((eof-object? ch) ch)
((char=? ch #\() ; If code section, then use
(got-code (read port))) ; \verb|read| to get code,
(else ; else skip this line as it
(text-mode-within-a-line)))))) ; is a comment.
(text-mode-within-a-line
(lambda () ; Ignore comments.
(let ((ch (read-char port)))
(cond ((eof-object? ch) ch)
((char=? ch #\newline)
(text-mode-and-saw-newline))
(else (text-mode-within-a-line))))))
(got-code
(lambda (code) ; Ignore the remainder of the
(let ((ch (read-char port))) ; last code line and return
(cond ((eof-object? ch) code) ; the results of \verb|read|.
((char=? ch #\newline)
code)
(else (got-code code)))))))
(text-mode-and-saw-newline) ; Start by looking
))) ; for a code line.
\end{document}
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