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mercury/library/pprint.m
Julien Fischer 0b92543c5e Fix more library documentation errors. 
library/*.m:
   As above.
2026-01-23 19:53:58 +11:00

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%---------------------------------------------------------------------------%
% vim:ts=4 sw=4 expandtab ft=mercury
%---------------------------------------------------------------------------%
% Copyright (C) 2000-2007, 2010-2011 The University of Melbourne
% Copyright (C) 2014-2018, 2020, 2022-2023, 2025-2026 The Mercury team.
% This file is distributed under the terms specified in COPYING.LIB.
%---------------------------------------------------------------------------%
%
% File: pprint.m.
% Main author: rafe
% Stability: high.
%
% NOTE: this module has now been superceded by pretty_printer.m, which
%
% - is more economical,
% - produces better output,
% - has better control over the amount of output produced, and
% - supports user-specifiable formatting for arbitrary types.
%
% ABOUT
% -----
%
% This started off as pretty much a direct transliteration of Philip Wadler's
% Haskell pretty printer described in "A Prettier Printer", available at
% http://cm.bell-labs.com/cm/cs/who/wadler/topics/recent.html
%
% Several changes have been made to the algorithm to preserve linear running
% time under a strict language, and to ensure scalability to extremely large
% terms without thrashing the VM system.
%
% Wadler's approach has three main advantages:
%
% 1. the layout algebra is small and quite intuitive (more so than Hughes');
% 2. the pretty printer is optimal in the sense that it will never generate
% output that over-runs the specified width unless that is unavoidable; and
% 3. the pretty printer is bounded in that it never needs to look more than
% k characters ahead to make a formatting decision.
%
% I have made the following changes:
%
% (a) rather than having group/1 as a non-primitive function (for allowing
% line-breaks to be converted into spaces at the pretty printer's discretion)
% over docs, I have extended the doc type to include a `GROUP' constructor,
% and made the appropriate algorithmic changes. Because `UNION' only arises
% as a consequence of processing a 'GROUP', it turns out to be simpler
% to do away with `UNION' altogether and convert clauses that process
% `UNION' terms to processing `GROUP's.
%
% (b) Flattened `line' breaks become empty strings rather than spaces.
%
% (c) The third change is the introduction of the `LABEL' constructor,
% which acts much like `NEST', except that indentation is defined
% using a string rather than a number of spaces. This is useful for,
% e.g., multi-line compiler errors and warnings that should be prefixed
% with the offending source file and line number.
%
% (d) The formatting decision procedure has been altered to preserve
% linear runtime behaviour in a strict language.
%
% (e) Naively marking up a term as a doc has the drawback that the
% resulting doc is significantly larger than the original term.
% Worse, any sharing structure in the original term leads to
% duplicated sub-docs, which can cause an exponential blow-up in the
% size of the doc w.r.t. the source term. To get around this problem
% I have introduced the 'DOC' constructor which causes on-demand
% conversion of arguments.
%
% [This is not true laziness in the sense that the 'DOC', once
% evaluated, will be overwritten with its value. This approach would
% lead to garbage retention and not solve the page thrashing behaviour
% otherwise experienced when converting extremely large terms.
% Instead, each 'DOC' is reevaluated each time it is examined.
% This trades off computation time for space.]
%
% I have added several obvious general purpose formatting functions.
%
%
% USAGE
% -----
%
% There are two stages in pretty printing an object of some type T:
% 1. convert the object to a pprint.doc using the constructor functions
% described below or by simply calling pprint.to_doc/[1,2];
% 2. call pprint.write/[4,5] or pprint.to_string/2 passing the display width
% and the doc.
%
%
% EXAMPLES
% --------
%
% The doc/1 type class has types string, char, int, float and doc as instances.
% Hence these types can all be converted to docs by applying doc/1.
% This happens automatically to the arguments of ++/2. Users may find it
% convenient to add other types as instances of the doc/1 type class.
%
% Below are some docs followed by the ways they might be displayed by the
% pretty printer given various line widths.
%
% 1. "Hello " ++ line ++ "world"
%
% Hello
% world
%
% 2. group("Hello " ++ line ++ "world")
%
% Hello world
%
% Hello
% world
%
% 3. group("Hello " ++ nest(3, line ++ "world"))
%
% Hello world
%
% Hello
% world
%
% 4. group("Goodbye " ++ nest(3, line ++ "cruel " ++ line ++ "world"))
%
% Goodbye cruel world
%
% Goodbye
% cruel
% world
%
% 5. group("Goodbye " ++ nest(3, line ++ group("cruel " ++ line ++ "world")))
%
% Goodbye cruel world
%
% Goodbye
% cruel world
%
% Goodbye
% cruel
% world
%
% 6. label("Look! ", line ++
% group("Goodbye " ++
% nest(3, line ++ group("cruel " ++ line ++ "world"))))
%
% Look! Goodbye cruel world
%
% Look! Goodbye
% Look! cruel world
%
% Look! Goodbye
% Look! cruel
% Look! world
%
%---------------------------------------------------------------------------%
%---------------------------------------------------------------------------%
:- module pprint.
:- interface.
:- import_module char.
:- import_module io.
:- import_module list.
:- import_module stream.
:- import_module string.
:- import_module univ.
%---------------------------------------------------------------------------%
% Clients must translate data structures into docs for
% the pretty printer to display.
%
:- type doc.
% This typeclass can be used to simplify the construction of docs.
%
:- typeclass doc(T) where [
% Convert a T to a doc, placing a limit on how much of the term
% will be fully converted as follows:
%
% doc(_, f ) = f
% doc(N, f(A, B, C)) = f/3 if N =< 0
% doc(N, f(A, B, C)) = some representation of the term whereby
% A is converted as doc(N - 1, A),
% B is converted as doc(N - 2, B), and
% C is converted as doc(N - 3, C)
% - if there are more than N arguments, the N+1th and subsequent
% arguments should be replaced with a single ellipsis.
%
func doc(int, T) = doc
].
:- instance doc(doc).
:- instance doc(string).
:- instance doc(int).
:- instance doc(int8).
:- instance doc(int16).
:- instance doc(int32).
:- instance doc(int64).
:- instance doc(uint).
:- instance doc(uint8).
:- instance doc(uint16).
:- instance doc(uint32).
:- instance doc(uint64).
:- instance doc(float).
:- instance doc(char).
%---------------------------------------------------------------------------%
%
% Creating a doc.
%
% The empty document corresponding to the null string.
%
:- func nil = doc.
% The document consisting of a single string.
%
% NOTE: since string is now an instance of the doc/1
% type class, it is simpler to just apply the doc/1
% method.
%
:- func text(string) = doc.
% This function can be used to convert strings, chars, ints, uints and
% floats to their text doc equivalents.
%
% NOTE: since these types are now instances of the doc/1 type class,
% it is simpler to just apply the doc/1 method to these types.
%
:- func poly(poly_type) = doc.
% The newline document. In a group doc (see below) the pretty printer
% may choose to instead `flatten' all line docs into nil docs in order
% to fit a doc on a single line.
%
:- func line = doc.
% Handy punctuation docs, and versions with following spaces and/or
% line breaks.
%
:- func comma = doc.
:- func semic = doc. % Semicolon.
:- func colon = doc.
:- func space = doc.
:- func comma_space = doc.
:- func semic_space = doc.
:- func colon_space = doc.
:- func comma_line = doc.
:- func semic_line = doc.
:- func colon_line = doc.
:- func space_line = doc.
:- func comma_space_line = doc.
:- func semic_space_line = doc.
:- func colon_space_line = doc.
:- func ellipsis = doc. % "...".
% Convert an instance of the doc/1 typeclass to a doc.
%
:- func doc(T) = doc <= (doc(T)).
% Convert an arbitrary term to a doc. This requires std_util.functor/3
% to work on all components of the object being converted. The second
% version places a maximum depth on terms which are otherwise truncated
% in the manner described in the documentation for the doc/2 method
% of the doc/1 type class.
%
% This may throw an exception or cause a runtime abort if the term
% in question has user-defined equality.
%
:- func to_doc(T) = doc.
:- func to_doc(int, T) = doc.
%---------------------------------------------------------------------------%
%
% Manipulating docs.
%
% The composition of two docs with no intervening space.
%
% NOTE: with the addition of the doc/1 type class, it is
% simpler to construct compound docs using ++/2.
%
:- func doc `<>` doc = doc.
% An alternative to the <>/2 concatenation operator that works
% on members of the doc/1 typeclass.
%
:- func T1 ++ T2 = doc <= (doc(T1), doc(T2)).
% Any `line' docs in the body that are not flattened out by the
% pretty printer are followed by the given number of spaces
% (nested `nest's add up).
%
:- func nest(int, T) = doc <= (doc(T)).
% Identical to a nest doc except that indentation is extended with
% a string label rather than some number of spaces.
%
:- func label(string, T) = doc <= (doc(T)).
% A group doc gives the pretty printer a choice: if the doc can be printed
% without line wrapping then it does so (all line, label, nest and group
% directives within the group are ignored); otherwise the pretty printer
% treats the group body literally, although nested group docs remain as
% choice points.
%
:- func group(T) = doc <= (doc(T)).
% Shorthand for doc ++ line ++ doc.
%
:- func doc `</>` doc = doc.
% Various bracketing functions.
%
% bracketed(L, R, Doc) = L ++ Doc ++ R
% parentheses(Doc) = bracketed("(", ")", Doc)
% brackets(Doc) = bracketed("[", "]", Doc)
% braces(Doc) = bracketed("{", "}", Doc)
%
:- func bracketed(T1, T2, T3) = doc <= (doc(T1), doc(T2), doc(T3)).
:- func parentheses(T) = doc <= (doc(T)).
:- func brackets(T) = doc <= (doc(T)).
:- func braces(T) = doc <= (doc(T)).
% packed(Sep, [X1, X2, .., Xn]) = G1 `<>` G2 `<>` .. `<>` Gn where
% Gi = group(line `<>` Xi `<>` Sep), except for Gn where
% Gn = group(line `<>` Xn).
%
% For the singleton list case, packed(Sep, [X]) = group(line `<>` X).
%
% The resulting doc tries to pack as many items on a line as possible.
%
:- func packed(T1, list(T2)) = doc <= (doc(T1), doc(T2)).
% A variant of the above whereby only the first N elements of the list
% are formatted and the rest are replaced by a single ellipsis.
%
:- func packed(int, T1, list(T2)) = doc <= (doc(T1), doc(T2)).
% packed_cs(Xs) = packed(comma_space, Xs).
%
% For example, to pretty print a Mercury list of docs one might use
%
% brackets(nest(2, packed_cs(Xs)))
%
:- func packed_cs(list(T)) = doc <= (doc(T)).
% A variant of the above whereby only the first N elements of the list
% are formatted and the rest are replaced by a single ellipsis.
%
:- func packed_cs(int, list(T)) = doc <= (doc(T)).
% This is like a depth-limited version of packed_cs/1 that first calls
% to_doc/2 on each member of the argument list.
%
:- func packed_cs_to_depth(int, list(T)) = doc.
% This is like a version of packed_cs_to_depth/1 that first calls
% univ_value/1 for each member of the argument list.
%
:- func packed_cs_univ_args(int, list(univ)) = doc.
% separated(PP, Sep, [X1,...,Xn]) =
% PP(X1) `<>` Sep `<>` ... Sep `<>` PP(Xn)
%
:- func separated(func(T1) = doc, T2, list(T1)) = doc <= (doc(T2)).
% Performs word wrapping at the end of line, taking whitespace sequences
% as delimiters separating words.
%
% See `char.is_whitespace' for the definition of whitespace characters
% used by this predicate.
%
:- func word_wrapped(string) = doc.
%---------------------------------------------------------------------------%
%
% Prettyprint a doc.
%
% Convert docs to pretty printed strings. The int argument specifies
% a line width in characters.
%
:- func to_string(int, doc) = string.
% Write the given doc out in its pretty printed format to the
% current output stream.
%
% The int argument specifies the preferred maximum length of each line.
% (This preferred maximum can be exceeded, e.g. if a single text string
% to be printed is longer than this width.)
%
:- pred write(int::in, T::in, io::di, io::uo) is det <= doc(T).
% Write the specified doc to the specified string writer stream
% in its pretty printed format.
%
% The int argument specifies the preferred maximum length of each line.
% (This preferred maximum can be exceeded, e.g. if a single text string
% to be printed is longer than this width.)
%
:- pred write(Stream::in, int::in, T::in, State::di, State::uo) is det
<= ( doc(T), stream.writer(Stream, string, State) ).
%---------------------------------------------------------------------------%
%---------------------------------------------------------------------------%
:- implementation.
:- import_module array.
:- import_module deconstruct.
:- import_module enum.
:- import_module int.
:- import_module int8.
:- import_module int16.
:- import_module int32.
:- import_module int64.
:- import_module map.
:- import_module ops.
:- import_module pair.
:- import_module robdd.
:- import_module sparse_bitset.
:- import_module term.
:- import_module type_desc.
:- import_module uint8.
:- import_module uint16.
:- import_module uint32.
:- import_module uint64.
:- import_module version_array.
%---------------------------------------------------------------------------%
:- type doc
---> pp_nil
; pp_text(string)
; pp_line
; pp_seq(doc, doc)
; pp_group(doc)
; pp_nest(int, doc)
; pp_label(string, doc)
; pp_doc(int, univ).
% pp_doc(MaxDepth, Univ)
% - Univ is the object to be converted to a doc via to_doc/3,
% represented as a univ.
% - MaxDepth is the depth limit before using ellipsis.
% This type is used to format key-value pairs in maps when
% using the generic to_doc/[1,2] functions.
%
:- type map_pair(K, V)
---> map_pair(K, V).
% Used for depth-limit arguments.
%
:- type depth == int.
%---------------------------------------------------------------------------%
:- instance doc(doc) where [doc(_, Doc) = Doc].
:- instance doc(string) where [doc(_, String) = text(String)].
:- instance doc(int) where [doc(_, I) = poly(i(I))].
:- instance doc(int8) where [doc(_, I8) = text(int8_to_string(I8))].
:- instance doc(int16) where [doc(_, I16) = text(int16_to_string(I16))].
:- instance doc(int32) where [doc(_, I32) = text(int32_to_string(I32))].
:- instance doc(int64) where [doc(_, I64) = text(int64_to_string(I64))].
:- instance doc(uint) where [doc(_, UI) = text(uint_to_string(UI))].
:- instance doc(uint8) where [doc(_, UI8) = text(uint8_to_string(UI8))].
:- instance doc(uint16) where [doc(_, UI16) = text(uint16_to_string(UI16))].
:- instance doc(uint32) where [doc(_, UI32) = text(uint32_to_string(UI32))].
:- instance doc(uint64) where [doc(_, UI64) = text(uint64_to_string(UI64))].
:- instance doc(float) where [doc(_, Float) = poly(f(Float))].
:- instance doc(char) where [doc(_, Char) = poly(c(Char))].
%---------------------------------------------------------------------------%
nil = pp_nil.
text(S) = pp_text(S).
poly(s(S)) = text(string.format("%s", [s(S)])).
poly(c(C)) = text(string.format("%c", [c(C)])).
poly(i(I)) = text(string.format("%d", [i(I)])).
poly(i8(I8)) = text(string.format("%d", [i(int8.cast_to_int(I8))])).
poly(i16(I16)) = text(string.format("%d", [i(int16.cast_to_int(I16))])).
poly(i32(I32)) = text(string.format("%d", [i(int32.cast_to_int(I32))])).
poly(i64(I64)) = text(string.format("%d", [i(int64.cast_to_int(I64))])).
poly(u(U)) = text(string.format("%u", [u(U)])).
poly(u8(U8)) = text(string.format("%u", [u(uint8.cast_to_uint(U8))])).
poly(u16(U16)) = text(string.format("%u", [u(uint16.cast_to_uint(U16))])).
poly(u32(U32)) = text(string.format("%u", [u(uint32.cast_to_uint(U32))])).
poly(u64(U64)) = text(string.format("%u", [u(uint64.cast_to_uint(U64))])).
poly(f(F)) = text(string.format("%f", [f(F)])).
line = pp_line.
%---------------------------------------------------------------------------%
comma = text(",").
semic = text(";").
colon = text(":").
space = text(" ").
comma_space = text(", ").
semic_space = text("; ").
colon_space = text(": ").
comma_line = "," ++ line.
semic_line = ";" ++ line.
colon_line = ":" ++ line.
space_line = " " ++ line.
comma_space_line = ", " ++ line.
semic_space_line = "; " ++ line.
colon_space_line = ": " ++ line.
ellipsis = text("...").
%---------------------------------------------------------------------------%
doc(X) = doc(int.max_int, X).
%---------------------------------------------------------------------------%
to_doc(X) = to_doc(int.max_int, X).
to_doc(Depth, X) = to_doc_prio(Depth, mercury_op_table_comma_priority, X).
%---------------------------------------------------------------------------%
X `<>` Y = pp_seq(X, Y).
Doc1 ++ Doc2 = doc(Doc1) `<>` doc(Doc2).
nest(I, X) = pp_nest(I, doc(X)).
label(L, X) = pp_label(L, doc(X)).
group(X) = pp_group(doc(X)).
%---------------------------------------------------------------------------%
X `</>` Y = X ++ line ++ Y.
%---------------------------------------------------------------------------%
bracketed(L, R, D) = L ++ D ++ R.
parentheses(D) = bracketed("(", ")", D).
brackets(D) = bracketed("[", "]", D).
braces(D) = bracketed("{", "}", D).
%---------------------------------------------------------------------------%
packed(Sep, Xs) = packed(int.max_int, Sep, Xs).
packed(_N, _Sep, []) =
nil.
packed(N, _Sep, [X]) =
group(line ++ (if 0 < N then doc(X) else ellipsis)).
packed(N, Sep, [X1, X2 | Xs]) =
( if 0 < N then
group(line ++ X1 ++ Sep) ++ packed(N - 1, Sep, [X2 | Xs])
else
group(line ++ ellipsis)
).
%---------------------------------------------------------------------------%
packed_cs(Xs) = packed(", ", Xs).
packed_cs(N, Xs) = packed(N, ", ", Xs).
%---------------------------------------------------------------------------%
packed_cs_to_depth(Depth, Xs) =
packed_cs(Depth, list.map(to_doc(Depth), Xs)).
%---------------------------------------------------------------------------%
packed_cs_univ_args(Depth, UnivArgs) =
packed_cs(Depth, list.map(func(UA) = pp_doc(Depth, UA), UnivArgs)).
%---------------------------------------------------------------------------%
separated(_, _, []) = nil.
separated(PP, Sep, [X | Xs]) = Doc :-
% XXX Using a helper predicate that takes X and Xs as separate arguments
% (and thus always works on a nonempty list) would do the same job
% with only one nil-vs-cons test per iteration.
(
Xs = [],
Doc = PP(X)
;
Xs = [_ | _],
Doc = PP(X) ++ (Sep ++ separated(PP, Sep, Xs))
).
%---------------------------------------------------------------------------%
word_wrapped(String) =
packed(space, list.map(func(Word) = text(Word),
string.words_separator(char.is_whitespace, String))).
%---------------------------------------------------------------------------%
% This may throw an exception or cause a runtime abort if the term
% in question has user-defined equality.
%
:- func to_doc_prio(int, priority, T) = doc.
to_doc_prio(Depth, Priority, X) =
( if dynamic_cast_to_var(X, Var) then
var_to_doc(Depth, Var)
else if dynamic_cast_to_sparse_bitset_of_int(X, SparseBitsetInt) then
sparse_bitset_to_doc(Depth, SparseBitsetInt)
else if dynamic_cast_to_sparse_bitset_of_var(X, SparseBitsetVar) then
sparse_bitset_to_doc(Depth, SparseBitsetVar)
else if dynamic_cast_to_list(X, List) then
list_to_doc(Depth, List)
else if dynamic_cast_to_array(X, Array) then
array_to_doc(Depth, Array)
else if dynamic_cast_to_version_array(X, VersionArray) then
version_array_to_doc(Depth, VersionArray)
else if dynamic_cast_to_tuple(X, Tuple) then
tuple_to_doc(Depth, Tuple)
else if dynamic_cast_to_map(X, Map) then
map_to_doc(Depth, Map)
else if dynamic_cast_to_map_pair(X, MapPair) then
map_pair_to_doc(Depth, MapPair)
else if dynamic_cast_to_robdd(X, Robdd) then
robdd_to_doc(Depth, Robdd)
else
generic_term_to_doc(Depth, Priority, X)
).
%---------------------------------------------------------------------------%
:- func generic_term_to_doc(depth, priority, T) = doc.
generic_term_to_doc(Depth, Priority, X) = Doc :-
( if Depth =< 0 then
functor(X, canonicalize, Name, Arity),
Doc = ( if Arity = 0 then text(Name) else Name ++ "/" ++ Arity )
else
deconstruct(X, canonicalize, Name, _Arity, UnivArgs),
Table = init_mercury_op_table,
( if
UnivArgs = [UnivArg],
lookup_prefix_op(Table, Name, OpPri, GtOrGe)
then
Doc = maybe_parens(Priority, OpPri,
Name ++
space ++
univ_to_doc(Depth - 1, OpPri `adjusted_by` GtOrGe, UnivArg)
)
else if
UnivArgs = [UnivArg],
lookup_postfix_op(Table, Name, OpPri, GtOrGe)
then
Doc = maybe_parens(Priority, OpPri,
univ_to_doc(Depth - 1, OpPri `adjusted_by` GtOrGe, UnivArg) ++
space ++
Name
)
else if
UnivArgs = [UnivArgL, UnivArgR],
lookup_infix_op(Table, Name, OpPri, GtOrGeL, GtOrGeR)
then
Doc = maybe_parens(Priority, OpPri,
univ_to_doc(Depth - 1, OpPri `adjusted_by` GtOrGeL,
UnivArgL) ++
space ++
Name ++
space ++
group(line ++
nest(2,
univ_to_doc(Depth - 2, OpPri `adjusted_by` GtOrGeR,
UnivArgR)
)
)
)
else if
UnivArgs = [UnivArgR1, UnivArgR2],
lookup_binary_prefix_op(Table, Name, OpPri, GtOrGeR1, GtOrGeR2)
then
Doc = maybe_parens(Priority, OpPri,
Name ++
space ++
univ_to_doc(Depth - 2, OpPri `adjusted_by` GtOrGeR1,
UnivArgR1) ++
space ++
group(line ++
nest(2,
univ_to_doc(Depth - 2, OpPri `adjusted_by` GtOrGeR2,
UnivArgR2)
)
)
)
else if
UnivArgs = []
then
Doc = text(Name)
else
Doc = group(
Name ++ parentheses(
nest(2, packed_cs_univ_args(Depth - 1, UnivArgs))
)
)
)
).
%---------------------------------------------------------------------------%
% We need to put parentheses around a subterm if its top-level
% functor has a higher priority than its parent functor.
%
:- func maybe_parens(priority, priority, doc) = doc.
maybe_parens(ParentPriority, OpPriority, Doc) =
( if priority_gt(ParentPriority, OpPriority) then
parentheses(Doc)
else
Doc
).
%---------------------------------------------------------------------------%
:- func priority `adjusted_by` arg_prio_gt_or_ge = priority.
adjusted_by(OpPriority, GtOrGe) = MinArgPriority :-
MinArgPriority = min_priority_for_arg(OpPriority, GtOrGe).
%---------------------------------------------------------------------------%
% Convert a univ encapsulated value into a doc.
%
:- func univ_to_doc(int, priority, univ) = doc.
univ_to_doc(Depth, Priority, Univ) =
to_doc_prio(Depth, Priority, univ_value(Univ)).
%---------------------------------------------------------------------------%
:- some [T2] pred dynamic_cast_to_var(T1::in, var(T2)::out) is semidet.
dynamic_cast_to_var(X, V) :-
% If X is a var then it has a type with one type argument.
[ArgTypeDesc] = type_args(type_of(X)),
% Convert ArgTypeDesc to a type variable ArgType.
(_ : ArgType) `has_type` ArgTypeDesc,
% Constrain the type of V to be var(ArgType) and do the cast.
dynamic_cast(X, V : var(ArgType)).
%---------------------------------------------------------------------------%
:- pred dynamic_cast_to_sparse_bitset_of_int(T1::in, sparse_bitset(int)::out)
is semidet.
dynamic_cast_to_sparse_bitset_of_int(X, A) :-
dynamic_cast(X, A : sparse_bitset(int)).
:- some [T2] pred dynamic_cast_to_sparse_bitset_of_var(T1::in,
sparse_bitset(var(T2))::out) is semidet.
dynamic_cast_to_sparse_bitset_of_var(X, A) :-
dynamic_cast(X, A : sparse_bitset(var)).
%---------------------------------------------------------------------------%
:- some [T2] pred dynamic_cast_to_version_array(T1::in,
version_array(T2)::out) is semidet.
dynamic_cast_to_version_array(X, VA) :-
% If X is a version array then it has a type with one type argument.
[ArgTypeDesc] = type_args(type_of(X)),
% Convert ArgTypeDesc to a type variable ArgType.
(_ : ArgType) `has_type` ArgTypeDesc,
% Constrain the type of VA to be array(ArgType) and do the cast.
dynamic_cast(X, VA : version_array(ArgType)).
%---------------------------------------------------------------------------%
:- some [T2] pred dynamic_cast_to_list(T1::in, list(T2)::out) is semidet.
dynamic_cast_to_list(X, L) :-
% If X is a list then it has a type with one type argument.
[ArgTypeDesc] = type_args(type_of(X)),
% Convert ArgTypeDesc to a type variable ArgType.
(_ : ArgType) `has_type` ArgTypeDesc,
% Constrain the type of L to be list(ArgType) and do the cast.
dynamic_cast(X, L : list(ArgType)).
%---------------------------------------------------------------------------%
:- some [T2, T3] pred dynamic_cast_to_map(T1::in, map(T2, T3)::out) is semidet.
dynamic_cast_to_map(X, M) :-
% If X is a map then it has a type with two type arguments.
[KeyTypeDesc, ValueTypeDesc] = type_args(type_of(X)),
% Convert the TypeDescs to type variables.
(_ : KeyType) `has_type` KeyTypeDesc,
(_ : ValueType) `has_type` ValueTypeDesc,
% Constrain the type of M to be map(KeyType, ValueType) and do the cast.
dynamic_cast(X, M : map(KeyType, ValueType)).
%---------------------------------------------------------------------------%
:- some [T2, T3] pred dynamic_cast_to_map_pair(T1::in, map_pair(T2, T3)::out)
is semidet.
dynamic_cast_to_map_pair(X, MP) :-
% If X is a map_pair then it has a type with two type arguments.
[KeyTypeDesc, ValueTypeDesc] = type_args(type_of(X)),
% Convert the TypeDescs to type variables.
(_ : KeyType) `has_type` KeyTypeDesc,
(_ : ValueType) `has_type` ValueTypeDesc,
% Constrain the type of MP to be map_pair(KeyType, ValueType)
% and do the cast.
dynamic_cast(X, MP : map_pair(KeyType, ValueType)).
%---------------------------------------------------------------------------%
:- pred dynamic_cast_to_tuple(T::in, T::out) is semidet.
dynamic_cast_to_tuple(X, X) :-
% If X is a tuple, then its functor name is {}.
functor(X, canonicalize, "{}", _Arity).
%---------------------------------------------------------------------------%
:- some [T2] pred dynamic_cast_to_robdd(T1, robdd(T2)).
:- mode dynamic_cast_to_robdd(in, out) is semidet.
dynamic_cast_to_robdd(X, R) :-
% If X is a robdd then it has a type with one type argument.
[ArgTypeDesc] = type_args(type_of(X)),
% Convert ArgTypeDesc to a type variable ArgType.
(_ : ArgType) `has_type` ArgTypeDesc,
% Constrain the type of R to be robdd(ArgType) and do the cast.
dynamic_cast(X, R : robdd(ArgType)).
%---------------------------------------------------------------------------%
:- func var_to_doc(int, var(T)) = doc.
var_to_doc(Depth, V) =
to_doc(Depth, to_int(V)).
%---------------------------------------------------------------------------%
% XXX Ideally we would just walk the sparse bitset.
% But that is an optimization for another day.
%
:- func sparse_bitset_to_doc(int, sparse_bitset(T)) = doc <= uenum(T).
sparse_bitset_to_doc(Depth, A) =
group("sparse_bitset" ++
parentheses(list_to_doc(Depth - 1, sparse_bitset.to_sorted_list(A)))).
%---------------------------------------------------------------------------%
:- func list_to_doc(int, list(T)) = doc.
list_to_doc(Depth, Xs) =
brackets(nest(1, packed_cs_to_depth(Depth - 1, Xs))).
%---------------------------------------------------------------------------%
% XXX Ideally we would just walk the array. But that is an optimization
% for another day.
%
:- func array_to_doc(int, array(T)) = doc.
array_to_doc(Depth, A) =
group("array" ++ parentheses(list_to_doc(Depth - 1, array.to_list(A)))).
%---------------------------------------------------------------------------%
% XXX Ideally we would just walk the version array. But that is
% an optimization for another day.
%
:- func version_array_to_doc(int, version_array(T)) = doc.
version_array_to_doc(Depth, A) =
group("version_array"
++ parentheses(list_to_doc(Depth - 1, version_array.to_list(A)))).
%---------------------------------------------------------------------------%
% This should only really be used if the item in question really
% is a tuple.
%
:- func tuple_to_doc(int, T) = doc.
tuple_to_doc(Depth, Tuple) = Doc :-
deconstruct(Tuple, canonicalize, _Name, _Arity, UnivArgs),
Doc = group(braces(nest(1, packed_cs_univ_args(Depth - 1, UnivArgs)))).
%---------------------------------------------------------------------------%
:- func map_to_doc(int, map(T1, T2)) = doc.
map_to_doc(Depth, X) = Doc :-
KVs = list.map(mk_map_pair, map.to_assoc_list(X)),
Doc = group("map" ++ parentheses(list_to_doc(Depth - 1, KVs))).
:- func mk_map_pair(pair(K, V)) = map_pair(K, V).
mk_map_pair(K - V) = map_pair(K, V).
%---------------------------------------------------------------------------%
:- func map_pair_to_doc(int, map_pair(T1, T2)) = doc.
map_pair_to_doc(Depth, map_pair(Key, Value)) =
to_doc(Depth - 1, Key) ++ text(" -> ") ++
group(nest(2, line ++ to_doc(Depth - 1, Value))).
%---------------------------------------------------------------------------%
:- func robdd_to_doc(int, robdd(T)) = doc.
robdd_to_doc(Depth, R) =
"robdd_dnf" ++ parentheses(list_to_doc(Depth - 1, dnf(R))).
%---------------------------------------------------------------------------%
to_string(Width, Doc) = Str :-
layout_best(pred(H::in, T::in, [H | T]::out) is det, Width, Doc, [], Strs),
Str = string.append_list(list.reverse(Strs)).
write(Width, Doc, !IO) :-
layout_best(io.write_string, Width, doc(Doc), !IO).
write(Stream, Width, Doc, !State) :-
layout_best(put(Stream), Width, doc(Doc), !State).
%---------------------------------------------------------------------------%
% This is a contraction of Wadler's pretty, layout and be functions,
% adapted to work with a strict evaluation order.
%
:- pred layout_best(pred(string, T, T), int, doc, T, T).
:- mode layout_best(in(pred(in, di, uo) is det), in, in, di, uo) is det.
:- mode layout_best(in(pred(in, in, out) is det), in, in, in, out) is det.
layout_best(AccPred, Width, Doc, !LayoutStream) :-
layout_best_acc(AccPred, Width, "", Doc, 0, _UsedWidth, !LayoutStream).
% layout_best_acc(AccPred, Width, AfterNlStr, Doc,
% !UsedWidth, !LayoutStream):
%
% AccPred is the predicate for accumulating output strings.
%
% Width is the number of characters on a line;
%
% AfterNlStr is the indentation string we should put after newlines.
%
% Doc is the doc to lay out.
%
% !UsedWidth is the number of characters laid out on the current line
% so far before and after laying out Doc.
%
% !LayoutStream is the layout stream before and after laying out Doc.
%
% This predicate is somewhat different to the function `be' described
% by Wadler. In the first place, the decision procedure has been
% recoded (in fits_flat/2) to preserve linear running times under
% a strict language. The second important change is that layout_best_acc/8
% handles output strings as they are identified (e.g. writing them
% out or accumulating them in a list), doing away with the need for
% a more elaborate simple_doc type.
%
:- pred layout_best_acc(pred(string, T, T), int, string, doc, int, int, T, T).
:- mode layout_best_acc(in(pred(in, di, uo) is det),
in, in, in, in, out, di, uo) is det.
:- mode layout_best_acc(in(pred(in, in, out) is det),
in, in, in, in, out, in, out) is det.
layout_best_acc(AccPred, Width, AfterNlStr, Doc, !UsedWidth, !LayoutStream) :-
(
Doc = pp_nil
;
Doc = pp_seq(DocA, DocB),
layout_best_acc(AccPred, Width, AfterNlStr, DocA,
!UsedWidth, !LayoutStream),
layout_best_acc(AccPred, Width, AfterNlStr, DocB,
!UsedWidth, !LayoutStream)
;
Doc = pp_nest(ExtraIndent, DocA),
NewAfterNlStr = AfterNlStr ++ string.duplicate_char(' ', ExtraIndent),
layout_best_acc(AccPred, Width, NewAfterNlStr, DocA,
!UsedWidth, !LayoutStream)
;
Doc = pp_label(LabelStr, DocA),
NewAfterNlStr = AfterNlStr ++ LabelStr,
layout_best_acc(AccPred, Width, NewAfterNlStr, DocA,
!UsedWidth, !LayoutStream)
;
Doc = pp_line,
!:UsedWidth = string.count_code_points(AfterNlStr),
AccPred("\n", !LayoutStream),
AccPred(AfterNlStr, !LayoutStream)
;
Doc = pp_group(DocA),
( if fits_flat(DocA, Width - !.UsedWidth) then
layout_flat(AccPred, DocA, !UsedWidth, !LayoutStream)
else
layout_best_acc(AccPred, Width, AfterNlStr, DocA,
!UsedWidth, !LayoutStream)
)
;
Doc = pp_doc(MaxDepth, Univ),
DocA = to_doc(MaxDepth, univ_value(Univ)),
layout_best_acc(AccPred, Width, AfterNlStr, DocA,
!UsedWidth, !LayoutStream)
;
Doc = pp_text(Text),
!:UsedWidth = !.UsedWidth + string.count_code_points(Text),
AccPred(Text, !LayoutStream)
).
%---------------------------------------------------------------------------%
% Decide if a flattened doc will fit on the remainder of the line.
%
:- pred fits_flat(doc::in, int::in) is semidet.
fits_flat(Doc, MaxWidth) :-
fits_flat_width_left(Doc, MaxWidth, _WidthLeft).
% Returns the width left on the line after formatting the given doc
% on a line with the given max width. Stops and fails as soon as
% the width left goes zero or negative.
% XXX The "goes zero" part is arguably a bug.
%
:- pred fits_flat_width_left(doc::in, int::in, int::out) is semidet.
fits_flat_width_left(Doc, WidthAvail, WidthLeft) :-
(
( Doc = pp_nil
; Doc = pp_line
),
WidthLeft = WidthAvail
;
Doc = pp_text(Str),
StrLen = string.count_code_points(Str),
WidthLeft = WidthAvail - StrLen,
WidthLeft > 0 % XXX This *could* be WidthLeft >= 0.
;
Doc = pp_seq(DocA, DocB),
fits_flat_width_left(DocA, WidthAvail, WidthLeftAfterA),
fits_flat_width_left(DocB, WidthLeftAfterA, WidthLeft)
;
( Doc = pp_group(DocA)
; Doc = pp_nest(_, DocA)
; Doc = pp_label(_, DocA) % XXX Why are we ignoring the labels?
),
fits_flat_width_left(DocA, WidthAvail, WidthLeft)
;
Doc = pp_doc(MaxDepth, Univ),
DocA = to_doc(MaxDepth, univ_value(Univ)),
fits_flat_width_left(DocA, WidthAvail, WidthLeft)
).
%---------------------------------------------------------------------------%
% Lay out a doc in its flattened form.
%
:- pred layout_flat(pred(string, T, T), doc, int, int, T, T).
:- mode layout_flat(in(pred(in, di, uo) is det), in, in, out, di, uo) is det.
:- mode layout_flat(in(pred(in, in, out) is det), in, in, out, in, out) is det.
layout_flat(AccPred, Doc, !UsedWidth, !LayoutStream) :-
(
( Doc = pp_nil
; Doc = pp_line
)
;
Doc = pp_text(Text),
!:UsedWidth = !.UsedWidth + string.count_code_points(Text),
AccPred(Text, !LayoutStream)
;
Doc = pp_seq(DocA, DocB),
layout_flat(AccPred, DocA, !UsedWidth, !LayoutStream),
layout_flat(AccPred, DocB, !UsedWidth, !LayoutStream)
;
( Doc = pp_group(DocA)
; Doc = pp_nest(_, DocA)
; Doc = pp_label(_, DocA)
),
layout_flat(AccPred, DocA, !UsedWidth, !LayoutStream)
;
Doc = pp_doc(MaxDepth, Univ),
DocA = to_doc(MaxDepth, univ_value(Univ)),
layout_flat(AccPred, DocA, !UsedWidth, !LayoutStream)
).
%---------------------------------------------------------------------------%
:- end_module pprint.
%---------------------------------------------------------------------------%
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