David,
Thanks for responding so promptly with documentation for the new scheme.
I have a query about this extract from your document:
"The consistent parameter indicates whether the block is to be broken
consistently (true) or not (false). If it is true then if the block will
not all fit on a line and must be broken then it will be broken at all
the breaks in the block whether this is necessary or not."
I think "all the breaks in the block" here is intended to means all the
PrettyBreak constructs appearing as immediate children of the
PrettyBlock construct (so that nested PrettyBlock constructs override
the outer setting of the consistent parameter). Is that right?
Regards,
Rob.
David Matthews wrote:
Rob,
I think the problem is actually with the wrapper function that is used
to emulate install_pp in terms of addPrettyPrinter. When I wrote a
version of your pretty printer directly in the new form (included below)
it worked as expected. I've now written a quick document describing the
new pretty printer ( http://www.polyml.org/docs/PrettyPrint.html ) so it
might be easier to convert your pretty printers if possible. I'll try
and see if I can fix install_pp but it's currently broken in SVN because
of some other changes.
Regards,
David
datatype TERM =
Num of int
| Plus of TERM * TERM;
local
open PolyML
fun term_pp depth unused (t: TERM) =
case t of
Num n => PrettyString (Int.toString n)
| Plus (t1, t2) =>
PrettyBlock(0, true, [],
[
term_pp depth unused t1,
PrettyBreak(1, 0),
PrettyString "+",
PrettyBreak(1, 0),
term_pp depth unused t2
])
in
fun pp flag depth unused t =
PrettyBlock(0, flag, [],
[
PrettyBlock(0, false, [],
[term_pp depth unused (t: TERM)])
])
end;
fun interval m n = (
let fun aux acc i = (
if i < m
then acc
else aux (i::acc) (i-1)
);
in aux [] n
end
);
PolyML.Compiler.lineLength := 40;
val _ = PolyML.addPrettyPrinter (pp false);
val t = foldr Plus (Num 0) (map Num (interval 1 40));
val _ = PolyML.addPrettyPrinter (pp true);
t;
Rob Arthan wrote:
I can't find any documentation for the new approach to pretty-printing
in version 5.3 of Poly/ML. For ProofPower, I am using the
PolyML.install_pp interface that is provided for backwards
compatibility. but it doesn't seem to give the same results. I find
that many things that used to print nicely spread over several lines
now print as one long thin column with only one or two symbols in each
column.
The problem seems to be with the interpretation of the boolean part of
the parameter to the function that begins a block. The attached code
shows a difference between 5.2 and 5.3. On 5.2 both times the value of
t t is pretty-printed you get the same results, which is one symbol
per line until what is left will fit all on one line. On 5.3, the
first time you get a sqaureish block and the second time you get one
symbol per line.
I can't find any documentation for the install_pp interface either so
I don't really know which behaviour is right.
Regards,
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