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fa5226ee67
library/*.m: Improve the documentation. Add a "Stability: low/medium/high" comment to all modules, which describes the stability of the interface to that module. ops.m: Add `:' as an infix operator. require.m: Implement require/1, since higher-order predicates now work. term.m: Use the type `comparison_result' from mercury_builtin.m, rather than defining an identical type `comparison'.
118 lines
3.3 KiB
Mathematica
118 lines
3.3 KiB
Mathematica
%---------------------------------------------------------------------------%
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% Copyright (C) 1995 University of Melbourne.
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% This file may only be copied under the terms of the GNU Library General
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% Public License - see the file COPYING.LIB in the Mercury distribution.
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%---------------------------------------------------------------------------%
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% File: stack.m.
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% Main author: fjh.
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% Stability: high.
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% This file contains a `stack' ADT.
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% Stacks are implemented here using lists.
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%--------------------------------------------------------------------------%
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:- module stack.
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:- interface.
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:- import_module int, std_util, list.
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:- type stack(_T).
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% `stack__init(Stack)' is true iff `Stack' is an empty stack.
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:- pred stack__init(stack(_T)).
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:- mode stack__init(out) is det.
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% `stack__is_empty(Stack)' is true iff `Stack' is an empty stack.
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:- pred stack__is_empty(stack(_T)).
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:- mode stack__is_empty(in) is semidet.
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% `stack__is_full(Stack)' is intended to be true iff `Stack'
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% is a stack whose capacity is exhausted. This
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% implement allows arbitrary-sized stacks, so stack__is_full
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% always fails.
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:- pred stack__is_full(stack(_T)).
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:- mode stack__is_full(in) is semidet.
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% `stack__push(Stack0, Elem, Stack)' is true iff `Stack' is
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% the stack which results from pushing `Elem' onto the top
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% of `Stack0'.
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:- pred stack__push(stack(T), T, stack(T)).
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:- mode stack__push(in, in, out) is det.
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% `stack__push_list(Stack0, Elems, Stack)' is true iff `Stack'
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% is the stack which results from pushing the elements of the
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% list `Elems' onto the top of `Stack0'.
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:- pred stack__push_list(stack(T), list(T), stack(T)).
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:- mode stack__push_list(in, in, out) is det.
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% `stack__top(Stack, Elem)' is true iff `Stack' is a non-empty
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% stack whose top element is `Elem'.
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:- pred stack__top(stack(T), T).
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:- mode stack__top(in, out) is semidet.
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% `stack__pop(Stack0, Elem, Stack)' is true iff `Stack0' is
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% a non-empty stack whose top element is `Elem', and `Stack'
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% the stack which results from popping `Elem' off `Stack0'.
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:- pred stack__pop(stack(T), T, stack(T)).
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:- mode stack__pop(in, out, out) is semidet.
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% `stack__pop_det' is like `stack__pop' except that it will
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% call error/1 rather than failing if given an empty stack.
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:- pred stack__pop_det(stack(T), T, stack(T)).
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:- mode stack__pop_det(in, out, out) is det.
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% `stack__depth(Stack, Depth)' is true iff `Stack' is a stack
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% containing `Depth' elements.
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:- pred stack__depth(stack(_T), int).
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:- mode stack__depth(in, out) is det.
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:- mode stack__depth(in, in) is semidet. % implied
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%--------------------------------------------------------------------------%
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:- implementation.
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:- import_module list, require.
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:- type stack(T) == list(T).
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stack__init([]).
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stack__is_empty([]).
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stack__is_full(_) :-
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semidet_fail.
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stack__push(Stack, Elem, [Elem | Stack]).
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stack__push_list(Stack, [], Stack).
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stack__push_list(Stack0, [Elem | Elems], Stack1) :-
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stack__push(Stack0, Elem, Stack2),
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stack__push_list(Stack2, Elems, Stack1).
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stack__top([Elem | _], Elem).
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stack__pop([Elem | Stack], Elem, Stack).
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stack__pop_det(Stack0, Elem, Stack) :-
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( Stack0 = [Elem1 | Stack1] ->
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Elem = Elem1,
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Stack = Stack1
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;
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error("stack__pop_det: pop from empty stack")
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).
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stack__depth(Stack, Depth) :-
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list__length(Stack, Depth).
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%--------------------------------------------------------------------------%
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