dak@sq.sq.com (David A Keldsen) (06/12/90)
OK, here's the promised summary. Thanks to all the folks who replied (quickly, too!). Fast overview: Emacs and vi can re-indent; emacs can do it in batch mode; fools lisp has pretty-printing code. A standalone re-indenter in C by wri!henry@uunet.uu.net is posted as a follow-up to this posting, in comp.lang.scheme only. Detailed summary: John R. Ellis (ellis@src.dec.com) points out that my initial request is ambiguous. Pretty-printers and a re-indenters are quite different beasts. A *pretty printer* is either a print procedure for an internal form, or is a code reformatter that is permitted to re-arrange the code. A *re-indenter* merely re-adjusts the indentation, and is not permitted to change the line splits. mob@media-lab.media.mit.edu, alms@cambridge.apple.com (Andrew L. M. Shalit), ted@NMSU.Edu, rees@parc.xerox.com, vladimir@Eng.Sun.COM (Vladimir G. Ivanovic) and Keiji Kanazawa <kgk@cs.brown.edu> all suggested Emacs. (This was before my revised specification that the code be free of encumbrances, small, and portable). For those free of these specifications, it was also noted that GNU emacs can be fired up in batch mode, for use as a stand-alone indenter. Tim Bradshaw <tim@cstr.edinburgh.ac.uk> offered the suggestion that in Common Lisp, it is easy to redefine the read table to keep comments (as asked in my second request). This isn't in the standard for Scheme, but it is supported in some implementations. donc@vaxa.isi.edu (Don Cohen) also suggested the readtable solution. J. A. Durieux <xerox@cs.vu.nl> and Jeff Mantei <uiucdcs!cs.uiuc.edu!mantei> both pointed out that vi has a lisp mode (:set lisp), and that =<addr> will lisp-indent the specified lines. =% was suggested as being especially useful; it re-indents to the matching parenthesis. (Note also that vi will start up in lisp mode, with auto-indent set, and show-matching-parentheses, if you use the -l option). Ozan Yigit <oz@nexus.yorku.ca> noted that the fools lisp distribution by Jonathan Lee (jonathan@scam.berkeley.edu) contains some nice pretty-printing code. And finally, wri!henry@uunet.uu.net sent the stand-alone re-indentation code, which I am posting as a follow-up to this article, in comp.lang.scheme only. -- // David A. 'Dak' Keldsen: dak@sq.com or utai[.toronto.edu]!sq!dak // "I have heard the mermaids singing, each to each." -- T.S.Eliot
dak@sq.sq.com (David A Keldsen) (06/12/90)
And here's the promised stand-alone indenter (in C).
----------------------------------------------------------------------
From: wri!henry@uunet.uu.net
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Date: Fri, 8 Jun 90 19:19:24 EDT
To: dak@sq.com
Here is a very simple indenter that I use all the time. Note, it doesn't
pretty print, just indent. I find that that is exactly what I want.
/*
* Indent a lisp (scheme) program.
* The only transformations performed are:
* Leading white space is replaced with 4 n spaces where n is the
* nesting level.
* Open and close square brackets (``['' and ``]'') are paired together
* and the latter are replaced with the correct number of close
* parens (``)'').
*/
#include <stdio.h>
#include <assert.h>
/*
* The following definitions make C more amenable to a purist.
*/
#define bool char /* boolean type */
#define uint unsigned int /* short names for unsigned types */
#define ulong unsigned long
#define uchar unsigned char
#define ushort unsigned short int
#define not ! /* logical negation operator */
#define and && /* logical conjunction */
#define or || /* logical disjunction */
#define TRUE (0 == 0)
#define FALSE (not TRUE)
#define loop while (TRUE) /* loop until break */
#define EOS '\0' /* end-of-string char */
#define NULL 0 /* invalid pointer */
#define cardof(a) (sizeof(a) / sizeof(*(a)))
#define endof(a) ((a) + cardof(a))
#define bitsof(a) (sizeof(a) * 8)
/*
* Function declarations that should be in stdio.h.
*/
extern char *malloc(),
*realloc();
#define ISPACE 4 /* distance to indent for each level */
#define TAB 8 /* distance between tab stops */
#define MAXSQ 32 /* maximum nesting of ``['' and ``]'' */
/*
* Note, an entry in sqs records the level BEFORE the cooresponding ``[''
* was seen.
*/
static int level, /* current ``('' level */
sqs[MAXSQ], /* stack of un-matched ``['' */
*sqtop = sqs - 1; /* top of sqs stack */
extern int main();
static void die(),
scan(),
doline(),
docomment(),
dostring();
static int doocto();
static void uplevel(),
downlevel();
static int skipws();
static void putws();
int
main()
{
scan();
return (0);
}
static void
die(fmt, arg)
char *fmt;
int arg;
{
fflush(stdout);
fprintf(stderr, fmt, arg);
fprintf(stderr, "\n");
exit(1);
}
static void
scan()
{
int ch;
loop
switch (ch = skipws()) {
case '\n':
putchar('\n');
continue;
case EOF:
if (level != 0)
die("%d missing ``)''.", level);
return;
default:
putws(ISPACE * level);
doline(ch);
putchar('\n');
}
}
static void
doline(ch)
int ch;
{
loop {
switch (ch) {
case '(':
uplevel(ch);
break;
case ')':
downlevel(ch);
break;
case '[':
uplevel(ch);
ch = '(';
break;
case ']':
downlevel(ch);
ch = ')';
break;
case ';':
docomment(ch);
return;
case '"':
dostring(ch);
ch = getchar();
continue;
case '#':
ch = doocto(ch);
continue;
case '\n':
case EOF:
return;
}
putchar(ch);
ch = getchar();
}
}
static void
docomment(ch)
int ch;
{
assert(ch == ';');
do {
putchar(ch);
ch = getchar();
} while (ch != '\n' && ch != EOF);
}
static void
dostring(ch)
int ch;
{
static bool warned = FALSE;
assert(ch == '\"');
loop {
putchar(ch);
ch = getchar();
switch (ch) {
case EOF:
putchar('\n');
die("Unterminated string");
case '\n':
if (not warned) {
warned = TRUE;
fprintf(stderr,
"Warning: new-line in string\n");
}
break;
case '"':
putchar(ch);
return;
case '\\':
putchar(ch);
ch = getchar();
if (ch == EOF) {
putchar('\n');
die("Unterminted string");
}
break;
}
}
}
static int
doocto(ch)
int ch;
{
assert(ch == '#');
putchar(ch);
ch = getchar();
switch (ch) {
case '\\':
putchar(ch);
ch = getchar();
if (ch == EOF) {
putchar('\n');
die("Unterminated character constant");
}
putchar(ch);
return (getchar());
default:
return (ch);
}
}
static void
uplevel(ch)
int ch;
{
switch (ch) {
case '(':
++level;
break;
case '[':
if (++sqtop == endof(sqs)) {
putchar('\n');
die("[ ... ] too deeply nested");
}
*sqtop = level++;
break;
default:
assert(FALSE);
}
}
static void
downlevel(ch)
int ch;
{
switch (ch) {
case ')':
--level;
if ((sqtop >= sqs)
and (level <= *sqtop)) {
putchar('\n');
die("Unmatched ``[''.");
}
if (level < 0) {
putchar('\n');
die("Too many ``)''.");
}
break;
case ']':
if (sqtop < sqs) {
putchar('\n');
die("Too many ``]''.");
}
assert(*sqtop >= 0);
if (--level != *sqtop) {
assert(level >= *sqtop);
putchar('\n');
die("``]'' seen but need %d ``)'' first",
level - *sqtop);
}
--sqtop;
break;
default:
assert(FALSE);
}
}
static int
skipws()
{
int ch;
loop
switch (ch = getchar()) {
case ' ':
case '\t':
break;
default:
return (ch);
}
}
static void
putws(len)
int len;
{
assert(len >= 0);
for (; len >= TAB; len -= TAB)
putchar('\t');
for (; len != 0; --len)
putchar(' ');
}
--
// David A. 'Dak' Keldsen: dak@sq.com or utai[.toronto.edu]!sq!dak
// "I have heard the mermaids singing, each to each." -- T.S.Eliot