1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
|
% -----------------------------------------------------------------------------
% (C) Altran Praxis Limited
% -----------------------------------------------------------------------------
%
% The SPARK toolset is free software; you can redistribute it and/or modify it
% under terms of the GNU General Public License as published by the Free
% Software Foundation; either version 3, or (at your option) any later
% version. The SPARK toolset is distributed in the hope that it will be
% useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
% Public License for more details. You should have received a copy of the GNU
% General Public License distributed with the SPARK toolset; see file
% COPYING3. If not, go to http://www.gnu.org/licenses for a complete copy of
% the license.
%
% =============================================================================
%###############################################################################
% PURPOSE
%-------------------------------------------------------------------------------
% Clauses to control formatting of vc output. These must appear in the user
% module.
%###############################################################################
%###############################################################################
% DEPENDENCIES
%###############################################################################
%###############################################################################
% TYPES
%###############################################################################
%###############################################################################
% DATA
%###############################################################################
/* Portray a BINARY operator */
portray(Term):-
nonvar(Term),
functor(Term, Name_Atom, 2),
arg(1,Term, A),
arg(2,Term, B),
/* Find a BINARY operator that matches */
current_op(Pred,F,Name_Atom),
(
F = xfx
;
F = yfx
;
F = xfy
),
/* Find the precedences of sub-terms A and B */
term_pri(A, AP),
term_pri(B, BP),
(
/* We parenthesize A in two cases: */
/* 1) For xfx operators, we parenthesize if A's functor is */
/* equal or lower in precedence to that of Term/ */
/* 2) If A's principal functor is lower precedence than that of Term, then */
/* we need to parenthesize A. */
/* Note that in ISO PROLOG, operator precedence numbers are SMALLER for */
/* more tightly binding operators, so we need the ">" operator to test */
/* for "lower precedence" here. */
(
F = xfx, /* Case 1 */
AP >= Pred
;
F \= xfx, /* Case 2 */
AP > Pred
),
write('('),
write_term(A, [priority(Pred), portrayed(true), portray(true), numbervars(true)]),
write(')')
;
(
F = xfx,
AP < Pred /* not Case 1 */
;
F \= xfx,
AP =< Pred /* not case 2 */
),
write_term(A, [priority(Pred), portrayed(true), portray(true), numbervars(true)])
),
write(' '),
write(Name_Atom),
write(' '),
(
/* If B's principal functor is lower or equal precedence than that of Term, then */
/* we need to parenthesize B */
/* This is to re-produce the POPLOG behaviour where multi-term expressions */
/* with equal-precedence operators are printed with the RHS parenthesised */
/* For example, we want "A + (B + C)" NOT "A + B + C" */
BP >= Pred,
write('('),
write_term(B, [priority(Pred), portrayed(true), portray(true), numbervars(true)]),
write(')')
;
BP < Pred,
write_term(B, [priority(Pred), portrayed(true), portray(true), numbervars(true)])
),
!.
/* Portray an UNARY operator of type fx or fy */
portray(Term):-
nonvar(Term),
functor(Term, Name_Atom, 1),
arg(1,Term, A),
/* Find a UNARY operator that matches */
(
current_op(Pred,fx,Name_Atom)
;
current_op(Pred,fy,Name_Atom)
),
/* Find the precedences of sub-term A */
term_pri(A, AP),
write(Name_Atom),
write(' '),
(
/* If A's principal functor is lower precedence than that of Term, then */
/* we need to parenthesize A */
AP > Pred,
write('('),
write_term(A, [priority(Pred), portrayed(true), portray(true), numbervars(true)]),
write(')')
;
AP =< Pred,
write_term(A, [priority(Pred), portrayed(true), portray(true), numbervars(true)])
),
!.
/* Portray an UNARY operator of type xf or yf */
portray(Term):-
nonvar(Term),
functor(Term, Name_Atom, 1),
arg(1,Term, A),
/* Find a UNARY operator that matches */
(
current_op(Pred,xf,Name_Atom)
;
current_op(Pred,yf,Name_Atom)
),
/* Find the precedences of sub-term B */
term_pri(A, AP),
(
/* If A's principal functor is lower precedence than that of Term, then */
/* we need to parenthesize A */
AP > Pred,
write('('),
write_term(A, [priority(Pred), portrayed(true), portray(true), numbervars(true)]),
write(')')
;
AP =< Pred,
write_term(A, [priority(Pred), portrayed(true), portray(true), numbervars(true)])
),
write(' '),
write(Name_Atom),
!.
/* Portray clauses for built-in PROLOG operators */
portray(List) :-
(List = [] ; List = [_|_]), !,
print_list(List).
/* Catch all - functor F, which is not an operator, with non-zero */
/* number of arguments - print as F(Args) with commas */
/* between the arguments. */
portray(X) :-
X =.. [F|Args],
atomic(F),
Args \== [],
!,
write(F),
write('('),
print_list1(Args),
write(')'),
!.
/* print_list/1 - prints a list enclosed in [ ] with */
/* comma and space between each element */
print_list(List) :-
write('['),
print_list1(List),
write(']').
print_list1([X]) :- !,
print(X).
print_list1([X|Xs]) :- !,
print(X),
write(', '),
print_list1(Xs).
print_list1([]).
/* term_pri/2 - returns the precedence of the principal functor of Term */
term_pri(Term, Prio) :-
/* Careful here to only look for BINARY operators */
nonvar(Term),
functor(Term, Name_Atom, 2),
(
current_op(Prio, xfx, Name_Atom)
;
current_op(Prio, yfx, Name_Atom)
;
current_op(Prio, xfy, Name_Atom)
).
term_pri(Term, Prio) :-
/* Careful here to only look for UNARY operators */
nonvar(Term),
functor(Term, Name_Atom, 1),
(
current_op(Prio, fx, Name_Atom)
;
current_op(Prio, fy, Name_Atom)
;
current_op(Prio, xf, Name_Atom)
;
current_op(Prio, yf, Name_Atom)
).
/* We don't want to parenthesise atoms, literals and so on, so we pretend */
/* that these have a very high precedence */
term_pri(_Term, Prio) :-
Prio = 1,
!.
%###############################################################################
% END-OF-FILE
|
