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https://github.com/Mercury-Language/mercury.git
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a4c18e979a
Estimated hours taken: 0.5 Most of the uses of the type `tree:tree/1' are lists of instructions. `tree__is_empty' is used to ask "was any code generated", but `tree__is_empty' fails for `node([])'. This has not been a problem in the past because the code generator builds up a trees of lists that are known to be non-empty. Parts of the RL generation code can create empty lists of instructions, and it can't hurt to test for this case elsewhere. compiler/tree.m: Added `tree__tree_of_lists_is_empty', which is similar to `tree__is_empty' except that `node([])' is also considered empty. compiler/lookup_switch.m: compiler/rl_gen.m: Use `tree__tree_of_lists_is_empty' instead of `tree__is_empty'.
68 lines
2.2 KiB
Mathematica
68 lines
2.2 KiB
Mathematica
%-----------------------------------------------------------------------------%
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% Copyright (C) 1993-1999 The University of Melbourne.
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% This file may only be copied under the terms of the GNU General
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% Public License - see the file COPYING in the Mercury distribution.
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%-----------------------------------------------------------------------------%
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%
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% Main authors: conway, fjh.
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%
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% This file provides a 'tree' data type.
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% The code generater uses this to build a tree of instructions and
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% then flatten them into a list.
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%
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%-----------------------------------------------------------------------------%
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%-----------------------------------------------------------------------------%
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:- module tree.
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%-----------------------------------------------------------------------------%
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:- interface.
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:- import_module list.
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:- type tree(T) ---> empty
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; node(T)
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; tree(tree(T), tree(T)).
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:- pred tree__flatten(tree(T), list(T)).
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:- mode tree__flatten(in, out) is det.
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:- pred tree__is_empty(tree(T)).
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:- mode tree__is_empty(in) is semidet.
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:- pred tree__tree_of_lists_is_empty(tree(list(T))).
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:- mode tree__tree_of_lists_is_empty(in) is semidet.
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%-----------------------------------------------------------------------------%
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:- implementation.
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tree__flatten(T, L) :-
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tree__flatten_2(T, [], L).
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:- pred tree__flatten_2(tree(T), list(T), list(T)).
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:- mode tree__flatten_2(in, in, out) is det.
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% flatten_2(T, L0, L) is true iff L is the list that results from
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% traversing T left-to-right depth-first, and then appending L0.
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tree__flatten_2(empty, L, L).
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tree__flatten_2(node(T), L, [T|L]).
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tree__flatten_2(tree(T1,T2), L0, L) :-
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tree__flatten_2(T2, L0, L1),
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tree__flatten_2(T1, L1, L).
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%-----------------------------------------------------------------------------%
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tree__is_empty(empty).
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tree__is_empty(tree(L, R)) :-
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tree__is_empty(L),
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tree__is_empty(R).
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%-----------------------------------------------------------------------------%
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tree__tree_of_lists_is_empty(empty).
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tree__tree_of_lists_is_empty(node([])).
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tree__tree_of_lists_is_empty(tree(L, R)) :-
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tree__tree_of_lists_is_empty(L),
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tree__tree_of_lists_is_empty(R).
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%-----------------------------------------------------------------------------%
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