/usr/lib/s9fes/pretty-print.scm is in scheme9 2010.11.13-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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; By Nils M Holm, 2009
; See the LICENSE file of the S9fES package for terms of use
;
; (pretty-print object <option> ...) ==> unspecific
; (pp object <option> ...) ==> unspecific
; (pp-file string <option> ...) ==> unspecific
; (pp-loop <option> ...) ==> unspecific
; (pp-string string <option> ...) ==> list
; (pp-string list <option> ...) ==> list
;
; (load-from-library "pretty-print.scm")
;
; Pretty-print Scheme objects, programs, or files. PRETTY-PRINT attempts
; to figure out whether OBJECT is a valid Scheme program. If so, it prints
; it as code and otherwise it prints it as data. The automatic detection
; can be disabled by passing an option to these procedures (see below).
;
; PP is just a less verbose name for PRETTY-PRINT.
;
; PP-FILE pretty-prints all objects in the file STRING.
;
; PP-LOOP pretty-prints all objects read from (current-input-stream).
;
; PP-STRING pretty-prints the form in STRING and returns a list
; containing one pretty-printed line per member (as strings).
; When a LIST is passed to PP-STRING instead of a STRING, it
; will assume it is a list of separate lines and append them with
; #\NEWLINEs in between.
;
; Any of these procedures accept the following <option>s that may be
; passed to it after the object to print:
;
; 'CODE Print OBJECT as if it was a Scheme program.
; 'DATA Print OBJECT as if it was a Scheme object.
; 'SIMPLE Attempt to keep some special forms in a single line,
; if they fit in one (IF, AND, OR, BEGIN, LAMBDA).
; 'MARGIN: n Set the right margin to N. The printer will attempt
; not to write any output beyond that margin. The default
; margin is at column 72.
; 'INDENT: n Indent all lines except for the first one by the given
; number of blanks (for embedding in editors).
; 'OUTPUT-PORT: p
; Send all output to the specified output port instead
; of (current-output-port).
;
; NOTE: This program handles only a subset of R4RS Scheme correctly
; and removes all comments from its input program. Caveat utilitor.
;
; Example: (pp-string '("(let ((a 1) (b 2))"
; "(cons a b))"))
; ==> ("(let ((a 1)"
; " (b 2))"
; " (cons a b))")
(load-from-library "programp.scm")
(load-from-library "for-all.scm")
(load-from-library "read-from-string.scm")
(load-from-library "write-to-string.scm")
(load-from-library "string-unsplit.scm")
; If your Scheme does not support FLUID-LET or DEFINE-MACRO,
; there is an alternative implementation using SYNTAX-RULES in
; lib/fluid-let-sr.scm.
(load-from-library "fluid-let.scm")
(define *Input* #f)
(define *Output* #f)
(define *Convert-unreadable* #f)
(define (read-form)
(if *Input*
(let ((form (if (null? *Input*)
'()
(read-from-string *Input*))))
(cond ((pair? form)
(set! *Input* (cdr form))
(car form))
((null? form)
#f)
(else
(set! *Output* (list #f form *Input*))
(set! *Input* '())
#f)))
(read)))
(define (end-of-input? x)
(if *Input*
(not x)
(eof-object? x)))
(define pretty-print
(let ((read-form read-form)
(end-of-input? end-of-input?))
(lambda (form . options)
(define *Margin* 72)
(define *Offset* 0)
(define *Column* 0)
(define *Output-port* (current-output-port))
(define *Print-as-code* #f)
(define *Print-as-data* #f)
(define *Print-newline* #f)
(define *Really-print* #t)
(define *Max-Column* 0)
(define *Simple* #f)
(define LP "(")
(define RP ")")
(define SP " ")
(define (pr-char c)
(if *Output*
(if (char=? #\newline c)
(begin (set-car! *Output*
(list->string (reverse! (car *Output*))))
(set! *Output* (cons '() *Output*)))
(set-car! *Output* (cons c (car *Output*))))
(write-char c *Output-port*)))
(define (pr-form x)
(if *Output*
(for-each pr-char
(string->list (display-to-string x)))
(display x *Output-port*)))
(define (atom? x)
(and (not (pair? x))
(not (null? x))
(not (vector? x))))
(define (object-length x)
(string-length (write-to-string x)))
(define (exceeds-margin? x . opt-lead)
(let ((lead (if (null? opt-lead)
0
(car opt-lead))))
(>= (+ *Column* lead (string-length (write-to-string x)))
*Margin*)))
(define (spaces n)
(and *Really-print*
(or (zero? n)
(begin (pr-char #\space)
(spaces (- n 1))))))
(define (linefeed)
(if *Really-print*
(pr-char #\newline))
(set! *Max-Column* *Margin*)
(spaces *Offset*)
(set! *Column* *Offset*))
(define (pr s)
(if *Really-print*
(pr-form s))
(set! *Column* (+ *Column* (string-length s)))
(if (> *Column* *Max-Column*)
(set! *Max-Column* *Column*)))
(define (really-simple? x)
(or (not (list? x))
(not (pair? x))
(not (memq (car x) '(lambda cond case do if and or let
let* letrec fluid-let begin)))))
(define (pp-simple-form x)
(if (or (not (list? x))
*Simple*
(for-all really-simple? x))
(let* ((s (write-to-string x))
(k (string-length s)))
(if (and (> (+ *Column* k) *Margin*)
(> *Column* *Offset*))
(linefeed))
(pr s))
(pp-inline-app x)))
(define (pp-datum x)
(cond ((or (null? x)
(symbol? x)
(boolean? x)
(char? x)
(number? x)
(string? x))
(pp-simple-form x))
((vector? x)
(if *Really-print*
(pr-char #\#))
(fluid-let ((*Offset* (+ 1 *Offset*)))
(pp-pair(vector->list x))))
((pair? x)
(pp-pair x))
((procedure? x)
(pp-simple-form (string->symbol "#<procedure>")))
(else
(error "pretty-print: unknown type" x))))
(define (pp-pair x)
(pr LP)
(fluid-let ((*Offset* (+ 1 *Offset*)))
(let pp-members ((x x)
(s #f))
(cond ((pair? x)
(if s
(if (or (pair? (car x))
(vector? (car x)))
(linefeed)
(pr SP)))
(pp-datum (car x))
(pp-members (cdr x) #t))
((not (null? x))
(pr " . ")
(pp-datum x)))))
(pr RP))
(define (pp-quote x q)
(pr q)
(fluid-let ((*Offset* (+ *Offset* (string-length q))))
(if (program? (cadr x))
(pp-form (cadr x))
(pp-datum (cadr x)))))
(define (pp-body x)
(cond ((not (null? x))
(pp-form (car x))
(if (not (null? (cdr x)))
(linefeed))
(pp-body (cdr x)))))
(define (pp-lambda x)
(cond ((or (not *Simple*)
(> (length x) 3)
(exceeds-margin? x))
(pr LP)
(pr "lambda ")
(fluid-let ((*Offset* (+ 2 *Offset*)))
(pp-datum (cadr x))
(linefeed)
(pp-body (cddr x))
(pr RP)))
(else
(pp-simple-form x))))
(define (fits-in-margin? formatter x)
(fluid-let ((*Column* *Column*)
(*Offset* *Offset*)
(*Max-Column* 0)
(*Really-print* #f))
(formatter x)
(< *Max-Column* *Margin*)))
(define (pp-inline-app x)
(pr LP)
(pp-simple-form (car x))
(if (not (null? (cdr x)))
(pr SP))
(fluid-let ((*Offset* (+ 2 (object-length (car x)) *Offset*)))
(pp-body (cdr x)))
(pr RP))
(define (pp-indented-app x)
(pr LP)
(fluid-let ((*Offset* (+ 1 *Offset*)))
(pp-form (car x)))
(let ((indent (if (pair? (car x)) 1 2)))
(fluid-let ((*Offset* (+ indent *Offset*)))
(if (not (null? (cdr x)))
(linefeed))
(pp-body (cdr x)))
(pr RP)))
(define (indented-style-preferred? x)
(and (memq x '(call-with-current-continuation
call/cc
call-with-input-file
call-with-output-file
with-input-from-file
with-output-to-file))
#t))
(define (pp-application x)
(cond ((fits-in-margin? pp-simple-form x)
(pp-simple-form x))
((indented-style-preferred? (car x))
(pp-indented-app x))
((fits-in-margin? pp-inline-app x)
(pp-inline-app x))
(else
(pp-indented-app x))))
(define (pp-cond/case what x)
(letrec
((print-clauses
(lambda (c*)
(cond ((not (null? c*))
(pr LP)
(fluid-let ((*Offset* (+ 1 *Offset*)))
(if (eq? what 'cond)
(pp-form (caar c*))
(pp-datum (caar c*))))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(if (and (eq? 'cond what)
(pair? (cdar c*))
(eq? '=> (cadar c*)))
(fluid-let ((*Offset* (+ 3 *Offset*)))
(pr "=> ")
(pp-body (cddar c*)))
(pp-body (cdar c*))))
(pr RP)
(if (not (null? (cdr c*)))
(linefeed))
(print-clauses (cdr c*)))))))
(pr LP)
(pr (symbol->string what))
(pr SP)
(fluid-let ((*Offset* (+ (if (eq? what 'cond) 6 2)
*Offset*)))
(if (eq? what 'case)
(begin (pp-simple-form (cadr x))
(linefeed)))
(let ((c* (if (eq? what 'cond)
(cdr x)
(cddr x))))
(print-clauses c*)
(pr RP)))))
(define (pp-do x)
(letrec
((print-inits
(lambda (x first)
(cond ((null? x)
#f)
(first
(pp-simple-form (car x))
(print-inits (cdr x) #f))
(else
(linefeed)
(pp-simple-form (car x))
(print-inits (cdr x) #f)))))
(init-part cadr)
(test-part caddr)
(do-body cdddr))
(pr LP)
(pr "do ")
(pr LP)
(fluid-let ((*Offset* (+ 5 *Offset*)))
(print-inits (init-part x) #t))
(fluid-let ((*Offset* (+ 4 *Offset*)))
(linefeed)
(pr LP)
(pp-form (car (test-part x)))
(if (not (null? (cdr (test-part x))))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-body (cdr (test-part x)))))
(pr RP))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-body (do-body x)))
(pr RP)))
(define (pp-just-indent what x)
(if (and *Simple*
(fits-in-margin? pp-simple-form x))
(pp-simple-form x)
(begin (pr LP)
(pr what)
(if (not (null? (cdr x)))
(pr SP))
(fluid-let ((*Offset* (+ 2 (string-length what) *Offset*)))
(let print ((x (cdr x)))
(cond ((not (null? x))
(pp-form (car x))
(if (not (null? (cdr x)))
(linefeed))
(print (cdr x)))))
(pr RP)))))
(define (pp-let-bindings b* rec)
(pr LP)
(fluid-let ((*Offset* (+ 1 *Offset*)))
(let pp-bindings ((b* b*))
(cond ((not (null? b*))
(pr LP)
(pp-simple-form (caar b*))
(cond ((and rec (pair? (cadar b*)))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-form (cadar b*))))
(else
(pr SP)
(fluid-let ((*Offset* (+ 2
(object-length (caar b*))
*Offset*)))
(pp-form (cadar b*)))))
(pr RP)
(if (not (null? (cdr b*)))
(linefeed))
(pp-bindings (cdr b*))))))
(pr RP))
(define (pp-let x)
(pr LP)
(pr "let ")
(let* ((named? (symbol? (cadr x)))
(bind (if named? (caddr x) (cadr x)))
(body (if named? (cdddr x) (cddr x)))
(name-len (if named?
(+ 1 (object-length (cadr x)))
0)))
(fluid-let ((*Offset* (+ 5 name-len *Offset*)))
(if named?
(begin (pp-simple-form (cadr x))
(pr SP)))
(pp-let-bindings bind #f))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-body body))
(pr RP)))
(define (pp-let* x)
(pr LP)
(pr "let* ")
(fluid-let ((*Offset* (+ 6 *Offset*)))
(pp-let-bindings (cadr x) #f))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-body (cddr x)))
(pr RP))
(define (pp-letrec x)
(pr LP)
(pr "letrec ")
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-let-bindings (cadr x) #t))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-body (cddr x)))
(pr RP))
(define (pp-fluid-let x)
(pr LP)
(pr "fluid-let ")
(fluid-let ((*Offset* (+ 11 *Offset*)))
(pp-let-bindings (cadr x) #f))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-body (cddr x)))
(pr RP))
(define (pp-define-etc what x)
(pr LP)
(pr what)
(pr SP)
(pp-simple-form (cadr x))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(if (or (and (pair? (caddr x))
(eq? 'lambda (caaddr x)))
(pair? (cadr x))
(exceeds-margin? x))
(linefeed)
(pr SP))
(pp-body (cddr x)))
(pr RP))
(define (pp-syntax-rules x)
(letrec
((pp-rules
(lambda (r*)
(cond ((not (null? r*))
(pr LP)
(pp-datum (caar r*))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-form (cadar r*))
(pr RP))
(if (not (null? (cdr r*)))
(linefeed))
(pp-rules (cdr r*)))))))
(pr LP)
(pr "syntax-rules ")
(fluid-let ((*Offset* (+ 14 *Offset*)))
(pp-datum (cadr x)))
(fluid-let ((*Offset* (+ 2 *Offset*)))
(linefeed)
(pp-rules (cddr x))
(pr RP))))
(define (pp-form x)
(if (not (pair? x))
(pp-datum x)
(case (car x)
((quote) (pp-quote x "'"))
((quasiquote) (pp-quote x "`"))
((unquote) (pp-quote x ","))
((unquote-splicing) (pp-quote x ",@"))
((lambda) (pp-lambda x))
((cond) (pp-cond/case 'cond x))
((case) (pp-cond/case 'case x))
((do) (pp-do x))
((if) (pp-just-indent "if" x))
((and) (pp-just-indent "and" x))
((or) (pp-just-indent "or" x))
((let) (pp-let x))
((let*) (pp-let* x))
((letrec) (pp-letrec x))
((fluid-let) (pp-fluid-let x)) ; S9fES ext.
((begin) (pp-just-indent "begin" x))
((define) (pp-define-etc "define" x))
((define-syntax) (pp-define-etc "define-syntax" x))
((syntax-rules) (pp-syntax-rules x))
(else (pp-application x)))))
(set! *Column* 0)
(set! *Offset* 0)
(set! *Margin* 72)
(set! *Print-as-code* #f)
(set! *Print-as-data* #f)
(set! *Print-newline* #f)
(set! *Simple* #f)
(set! *Convert-unreadable* #f)
(let loop ((options options))
(cond ((null? options)
(cond ((and *Print-as-code*
*Print-as-data*)
(error (string-append
"pretty-print: please specify either the"
" CODE or DATA option, but not both")))
(*Print-newline*)
(*Print-as-code*
(pp-form form))
(*Print-as-data*
(pp-datum form))
((program? form)
(pp-form form))
(else
(pp-datum form))))
((eq? 'code (car options))
(set! *Print-as-code* #t)
(loop (cdr options)))
((eq? 'data (car options))
(set! *Print-as-data* #t)
(loop (cdr options)))
((eq? 'linefeed (car options))
(set! *Print-newline* #t)
(loop (cdr options)))
((eq? 'simple (car options))
(set! *Simple* #t)
(loop (cdr options)))
((eq? 'indent: (car options))
(if (null? (cdr options))
(error "pretty-print: missing argument to INDENT:"))
(if (not (number? (cadr options)))
(error "pretty-print: non-numeric argument to INDENT:"))
(set! *Offset* (cadr options))
(loop (cddr options)))
((eq? 'margin: (car options))
(if (null? (cdr options))
(error "pretty-print: missing argument to MARGIN:"))
(if (not (number? (cadr options)))
(error "pretty-print: non-numeric argument to MARGIN:"))
(set! *Margin* (cadr options))
(loop (cddr options)))
((eq? 'output-port: (car options))
(if (null? (cdr options))
(error "pretty-print: missing argument to OUTPUT-PORT:"))
(if (not (output-port? (cadr options)))
(error "pretty-print: expected port in OUTPUT-PORT:"))
(set! *Output-port* (cadr options))
(loop (cddr options)))
(else
(error "pretty-print: unknown option"
(car options)))))
(linefeed))))
(define pp pretty-print)
(define (pp-loop . options)
(let pp* ((x (read-form)))
(cond ((not (end-of-input? x))
(apply pp x options)
(let ((next (read-form)))
(if (not (end-of-input? next))
(pp #f 'linefeed))
(pp* next))))))
(define (pp-file file . options)
(with-input-from-file
file
(lambda ()
(apply pp-loop options))))
(define (pp-string str* . options)
(set! *Input* (if (string? str*)
str*
(string-unsplit #\newline str*)))
(set! *Output* (list '()))
(apply pp-loop options)
(reverse! (cdr *Output*)))
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