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44 (define-module (ice-9 pretty-print)
45 :export (pretty-print))
49 ;;"genwrite.scm" generic write used by pretty-print and truncated-print.
50 ;; Copyright (c) 1991, Marc Feeley
51 ;; Author: Marc Feeley (feeley@iro.umontreal.ca)
52 ;; Distribution restrictions: none
54 (define genwrite:newline-str (make-string 1 #\newline))
56 (define (generic-write obj display? width output)
58 (define (read-macro? l)
59 (define (length1? l) (and (pair? l) (null? (cdr l))))
60 (let ((head (car l)) (tail (cdr l)))
62 ((quote quasiquote unquote unquote-splicing) (length1? tail))
65 (define (read-macro-body l)
68 (define (read-macro-prefix l)
69 (let ((head (car l)) (tail (cdr l)))
74 ((unquote-splicing) ",@"))))
77 (and col (output str) (+ col (string-length str))))
81 (define (wr-expr expr col)
82 (if (read-macro? expr)
83 (wr (read-macro-body expr) (out (read-macro-prefix expr) col))
86 (define (wr-lst l col)
88 (let loop ((l (cdr l))
89 (col (and col (wr (car l) (out "(" col)))))
92 (loop (cdr l) (wr (car l) (out " " col))))
93 ((null? l) (out ")" col))
94 (else (out ")" (wr l (out " . " col))))))
97 (cond ((pair? obj) (wr-expr obj col))
98 ((null? obj) (wr-lst obj col))
99 ((vector? obj) (wr-lst (vector->list obj) (out "#" col)))
100 ((boolean? obj) (out (if obj "#t" "#f") col))
101 ((number? obj) (out (number->string obj) col))
102 ((symbol? obj) (out (symbol->string obj) col))
103 ((procedure? obj) (out "#[procedure]" col))
104 ((string? obj) (if display?
106 (let loop ((i 0) (j 0) (col (out "\"" col)))
107 (if (and col (< j (string-length obj)))
108 (let ((c (string-ref obj j)))
109 (if (or (char=? c #\\)
114 (out (substring obj i j)
116 (loop i (+ j 1) col)))
118 (out (substring obj i j) col))))))
119 ((char? obj) (if display?
120 (out (make-string 1 obj) col)
123 ((#\newline) "newline")
124 (else (make-string 1 obj)))
126 (else (out (object->string obj) col))))
130 (define (spaces n col)
133 (spaces (- n 8) (out " " col))
134 (out (substring " " 0 n) col))
137 (define (indent to col)
140 (and (out genwrite:newline-str col) (spaces to 0))
141 (spaces (- to col) col))))
143 (define (pr obj col extra pp-pair)
144 (if (or (pair? obj) (vector? obj)) ; may have to split on multiple lines
146 (left (min (+ (- (- width col) extra) 1) max-expr-width)))
147 (generic-write obj display? #f
149 (set! result (cons str result))
150 (set! left (- left (string-length str)))
152 (if (> left 0) ; all can be printed on one line
153 (out (reverse-string-append result) col)
155 (pp-pair obj col extra)
156 (pp-list (vector->list obj) (out "#" col) extra pp-expr))))
159 (define (pp-expr expr col extra)
160 (if (read-macro? expr)
161 (pr (read-macro-body expr)
162 (out (read-macro-prefix expr) col)
165 (let ((head (car expr)))
167 (let ((proc (style head)))
169 (proc expr col extra)
170 (if (> (string-length (symbol->string head))
172 (pp-general expr col extra #f #f #f pp-expr)
173 (pp-call expr col extra pp-expr))))
174 (pp-list expr col extra pp-expr)))))
179 (define (pp-call expr col extra pp-item)
180 (let ((col* (wr (car expr) (out "(" col))))
182 (pp-down (cdr expr) col* (+ col* 1) extra pp-item))))
187 (define (pp-list l col extra pp-item)
188 (let ((col (out "(" col)))
189 (pp-down l col col extra pp-item)))
191 (define (pp-down l col1 col2 extra pp-item)
192 (let loop ((l l) (col col1))
195 (let ((rest (cdr l)))
196 (let ((extra (if (null? rest) (+ extra 1) 0)))
198 (pr (car l) (indent col2 col) extra pp-item)))))
204 (indent col2 (out "." (indent col2 col)))
208 (define (pp-general expr col extra named? pp-1 pp-2 pp-3)
210 (define (tail1 rest col1 col2 col3)
211 (if (and pp-1 (pair? rest))
212 (let* ((val1 (car rest))
214 (extra (if (null? rest) (+ extra 1) 0)))
215 (tail2 rest col1 (pr val1 (indent col3 col2) extra pp-1) col3))
216 (tail2 rest col1 col2 col3)))
218 (define (tail2 rest col1 col2 col3)
219 (if (and pp-2 (pair? rest))
220 (let* ((val1 (car rest))
222 (extra (if (null? rest) (+ extra 1) 0)))
223 (tail3 rest col1 (pr val1 (indent col3 col2) extra pp-2)))
224 (tail3 rest col1 col2)))
226 (define (tail3 rest col1 col2)
227 (pp-down rest col2 col1 extra pp-3))
229 (let* ((head (car expr))
231 (col* (wr head (out "(" col))))
232 (if (and named? (pair? rest))
233 (let* ((name (car rest))
235 (col** (wr name (out " " col*))))
236 (tail1 rest (+ col indent-general) col** (+ col** 1)))
237 (tail1 rest (+ col indent-general) col* (+ col* 1)))))
239 (define (pp-expr-list l col extra)
240 (pp-list l col extra pp-expr))
242 (define (pp-LAMBDA expr col extra)
243 (pp-general expr col extra #f pp-expr-list #f pp-expr))
245 (define (pp-IF expr col extra)
246 (pp-general expr col extra #f pp-expr #f pp-expr))
248 (define (pp-COND expr col extra)
249 (pp-call expr col extra pp-expr-list))
251 (define (pp-CASE expr col extra)
252 (pp-general expr col extra #f pp-expr #f pp-expr-list))
254 (define (pp-AND expr col extra)
255 (pp-call expr col extra pp-expr))
257 (define (pp-LET expr col extra)
258 (let* ((rest (cdr expr))
259 (named? (and (pair? rest) (symbol? (car rest)))))
260 (pp-general expr col extra named? pp-expr-list #f pp-expr)))
262 (define (pp-BEGIN expr col extra)
263 (pp-general expr col extra #f #f #f pp-expr))
265 (define (pp-DO expr col extra)
266 (pp-general expr col extra #f pp-expr-list pp-expr-list pp-expr))
268 ; define formatting style (change these to suit your style)
270 (define indent-general 2)
272 (define max-call-head-width 5)
274 (define max-expr-width 50)
278 ((lambda let* letrec define) pp-LAMBDA)
288 (pr obj col 0 pp-expr))
291 (out genwrite:newline-str (pp obj 0))
293 ;; Return `unspecified'
296 ; (reverse-string-append l) = (apply string-append (reverse l))
298 (define (reverse-string-append l)
300 (define (rev-string-append l i)
303 (len (string-length str))
304 (result (rev-string-append (cdr l) (+ i len))))
305 (let loop ((j 0) (k (- (- (string-length result) i) len)))
308 (string-set! result k (string-ref str j))
309 (loop (+ j 1) (+ k 1)))
313 (rev-string-append l 0))
315 ;"pp.scm" Pretty-Print
316 (define (pretty-print obj . opt)
317 (let ((port (if (pair? opt) (car opt) (current-output-port))))
318 (generic-write obj #f 79
319 (lambda (s) (display s port) #t))))