lots of internal cleaning and tuning;
removed {parse,print}_{pre,post}_proc;
new lexer: now human readable due to scanner combinators;
new parser installed, but still inactive (due to grammar ambiguities);
added Syntax.test_read;
typ_of_term: sorts now made distinct and sorted;
mixfix: added forced line breaks (//);
PROP now printed before subterm of type prop with non-const head;
(* Title: Pure/Syntax/pretty.ML
ID: $Id$
Author: Lawrence C Paulson
Copyright 1991 University of Cambridge
Generic pretty printing module.
Loosely based on
D. C. Oppen, "Pretty Printing",
ACM Transactions on Programming Languages and Systems (1980), 465-483.
The object to be printed is given as a tree with indentation and line
breaking information. A "break" inserts a newline if the text until
the next break is too long to fit on the current line. After the newline,
text is indented to the level of the enclosing block. Normally, if a block
is broken then all enclosing blocks will also be broken. Only "inconsistent
breaks" are provided.
The stored length of a block is used in breakdist (to treat each inner block as
a unit for breaking).
*)
type pprint_args = (string -> unit) * (int -> unit) * (int -> unit) *
(unit -> unit) * (unit -> unit);
signature PRETTY =
sig
type T
val blk: int * T list -> T
val brk: int -> T
val fbrk: T
val str: string -> T
val lst: string * string -> T list -> T
val quote: T -> T
val string_of: T -> string
val str_of: T -> string
val pprint: T -> pprint_args -> unit
val setdepth: int -> unit
val setmargin: int -> unit
end;
functor PrettyFun () : PRETTY =
struct
(*Printing items: compound phrases, strings, and breaks*)
datatype T = Block of T list * int * int (*indentation, length*)
| String of string
| Break of bool*int (*mandatory flag; width if not taken*);
(*Add the lengths of the expressions until the next Break; if no Break then
include "after", to account for text following this block. *)
fun breakdist (Block(_,_,len)::es, after) = len + breakdist(es, after)
| breakdist (String s :: es, after) = size s + breakdist (es, after)
| breakdist (Break _ :: es, after) = 0
| breakdist ([], after) = after;
fun repstring a 0 = ""
| repstring a 1 = a
| repstring a k =
if k mod 2 = 0 then repstring(a^a) (k div 2)
else repstring(a^a) (k div 2) ^ a;
(*** Type for lines of text: string, # of lines, position on line ***)
type text = {tx: string, nl: int, pos: int};
val emptytext = {tx="", nl=0, pos=0};
fun blanks wd {tx,nl,pos} =
{tx = tx ^ repstring" "wd,
nl = nl,
pos = pos+wd};
fun newline {tx,nl,pos} =
{tx = tx ^ "\n",
nl = nl+1,
pos = 0};
fun string s {tx,nl,pos} =
{tx = tx ^ s,
nl = nl,
pos = pos + size(s)};
(*** Formatting ***)
val margin = ref 80 (*right margin, or page width*)
and breakgain = ref 4 (*minimum added space required of a break*)
and emergencypos = ref 40; (*position too far to right*)
fun setmargin m =
(margin := m;
breakgain := !margin div 20;
emergencypos := !margin div 2);
fun forcenext [] = []
| forcenext (Break(_,wd) :: es) = Break(true,0) :: es
| forcenext (e :: es) = e :: forcenext es;
fun format ([], _, _) text = text
| format (e::es, blockin, after) (text as {pos,nl,...}) =
(case e of
Block(bes,indent,wd) =>
let val blockin' = (pos + indent) mod !emergencypos
val btext = format(bes, blockin', breakdist(es,after)) text
val es2 = if nl < #nl(btext) then forcenext es
else es
in format (es2,blockin,after) btext end
| String s => format (es,blockin,after) (string s text)
| Break(force,wd) => (* no break if text fits on this line
or if breaking would add only breakgain to space *)
format (es,blockin,after)
(if not force andalso
pos+wd <= max[!margin - breakdist(es,after),
blockin + !breakgain]
then blanks wd text
else blanks blockin (newline text)));
(*** Exported functions to create formatting expressions ***)
fun length (Block(_,_,len)) = len
| length (String s) = size s
| length (Break(_,wd)) = wd;
val str = String
and fbrk = Break(true,0);
fun brk wd = Break(false,wd);
fun blk (indent,es) =
let fun sum([], k) = k
| sum(e::es, k) = sum(es, length e + k)
in Block(es,indent, sum(es,0)) end;
fun lst(lp,rp) es =
let fun add(e,es) = str"," :: brk 1 :: e :: es;
fun list(e :: (es as _::_)) = str lp :: e :: foldr add (es,[str rp])
| list(e::[]) = [str lp, e, str rp]
| list([]) = []
in blk(size lp, list es) end;
fun quote prt = blk (1, [str "\"", prt, str "\""]);
(*** Pretty printing with depth limitation ***)
val depth = ref 0; (*maximum depth; 0 means no limit*)
fun setdepth dp = (depth := dp);
fun pruning dp (Block(bes,indent,wd)) =
if dp>0 then blk(indent, map (pruning(dp-1)) bes)
else String"..."
| pruning dp e = e;
fun prune dp e = if dp>0 then pruning dp e else e;
fun string_of e = #tx (format ([prune (!depth) e],0,0) emptytext);
fun str_of prt =
let
fun s_of (Block (prts, _, _)) = implode (map s_of prts)
| s_of (String s) = s
| s_of (Break (false, wd)) = repstring " " wd
| s_of (Break (true, _)) = " ";
in
s_of (prune (! depth) prt)
end;
fun pprint prt (put_str, begin_blk, put_brk, put_fbrk, end_blk) =
let
fun pp (Block (prts, ind, _)) = (begin_blk ind; pp_lst prts; end_blk ())
| pp (String s) = put_str s
| pp (Break (false, wd)) = put_brk wd
| pp (Break (true, _)) = put_fbrk ()
and pp_lst [] = ()
| pp_lst (prt :: prts) = (pp prt; pp_lst prts);
in
pp (prune (! depth) prt)
end;
(*** Initialization ***)
val () = setmargin 80;
end;