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
|
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
/* $Rev$ $Date$ */
#ifndef tuscany_scheme_environment_hpp
#define tuscany_scheme_environment_hpp
/**
* Script evaluator environment implementation.
*/
#include "string.hpp"
#include "list.hpp"
#include "value.hpp"
#include "primitive.hpp"
#include <string>
namespace tuscany {
namespace scheme {
typedef value Frame;
typedef list<value> Env;
const value trueSymbol("true");
const value falseSymbol("false");
const value defineSymbol("define");
const value setSymbol("set!");
const value dotSymbol(".");
const Env theEmptyEnvironment() {
return nilListValue;
}
const bool isDefinition(const value& exp) {
return isTaggedList(exp, defineSymbol);
}
const bool isAssignment(const value& exp) {
return isTaggedList(exp, setSymbol);
}
const bool isVariable(const value& exp) {
return isSymbol(exp);
}
const Env enclosingEnvironment(const Env& env) {
return cdr(env);
}
const gc_ptr<Frame> firstFrame(const Env& env) {
return car(env);
}
const list<value> frameVariables(const Frame& frame) {
return car((list<value> )frame);
}
const list<value> frameValues(const Frame& frame) {
return cdr((list<value> )frame);
}
const bool isDotVariable(const value& var) {
return var == dotSymbol;
}
const Frame makeBinding(const Frame& frameSoFar, const list<value>& variables, const list<value> values) {
if (isNull(variables)) {
if (!isNull(values))
logStream() << "Too many arguments supplied " << values << endl;
return frameSoFar;
}
if (isDotVariable(car(variables)))
return makeBinding(frameSoFar, cdr(variables), mklist<value>(values));
if (isNull(values)) {
if (!isNull(variables))
logStream() << "Too few arguments supplied " << variables << endl;
return frameSoFar;
}
const list<value> vars = cons(car(variables), frameVariables(frameSoFar));
const list<value> vals = cons(car(values), frameValues(frameSoFar));
const Frame newFrame = cons(value(vars), vals);
return makeBinding(newFrame, cdr(variables), cdr(values));
}
const gc_ptr<Frame> makeFrame(const list<value>& variables, const list<value> values) {
const gc_ptr<Frame> frame = new (gc_new<Frame>()) Frame(makeBinding(cons(value(nilListValue), nilListValue), variables, values));
return frame;
}
const value definitionVariable(const value& exp) {
const list<value> exps(exp);
if(isSymbol(car(cdr(exps))))
return car(cdr(exps));
const list<value> lexps(car(cdr(exps)));
return car(lexps);
}
const value definitionValue(const value& exp) {
const list<value> exps(exp);
if(isSymbol(car(cdr(exps)))) {
if (isNull(cdr(cdr(exps))))
return nilValue;
return car(cdr(cdr(exps)));
}
const list<value> lexps(car(cdr(exps)));
return makeLambda(cdr(lexps), cdr(cdr(exps)));
}
const value assignmentVariable(const value& exp) {
return car(cdr((list<value> )exp));
}
const value assignmentValue(const value& exp) {
return car(cdr(cdr((list<value> )exp)));
}
const Frame addBindingToFrame(const value& var, const value& val, const Frame& frame) {
return cons(value(cons(var, frameVariables(frame))), cons(val, frameValues(frame)));
}
const bool defineVariable(const value& var, const value& val, Env& env) {
const Frame newFrame = addBindingToFrame(var, val, *firstFrame(env));
setvalue(*firstFrame(env), addBindingToFrame(var, val, *firstFrame(env)));
return true;
}
const Env extendEnvironment(const list<value>& vars, const list<value>& vals, const Env& baseEnv) {
return cons<value>(makeFrame(vars, vals), baseEnv);
}
const Env setupEnvironment() {
Env env = extendEnvironment(primitiveProcedureNames(), primitiveProcedureObjects(), theEmptyEnvironment());
defineVariable(trueSymbol, true, env);
defineVariable(falseSymbol, false, env);
return env;
}
const value lookupEnvLoop(const value& var, const Env& env);
const value lookupEnvScan(const value& var, const list<value>& vars, const list<value>& vals, const Env& env) {
if(isNull(vars))
return lookupEnvLoop(var, enclosingEnvironment(env));
if(var == car(vars))
return car(vals);
return lookupEnvScan(var, cdr(vars), cdr(vals), env);
}
const value lookupEnvLoop(const value& var, const Env& env) {
if(env == theEmptyEnvironment()) {
logStream() << "Unbound variable " << var << endl;
return nilValue;
}
return lookupEnvScan(var, frameVariables(*firstFrame(env)), frameValues(*firstFrame(env)), env);
}
const value lookupVariableValue(const value& var, const Env& env) {
return lookupEnvLoop(var, env);
}
}
}
#endif /* tuscany_scheme_environment_hpp */
|
