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
|
//: Structured programming
//:
//: Our jump operators are quite inconvenient to use, so mu provides a
//: lightweight tool called 'transform_braces' to work in a slightly more
//: convenient format with nested braces:
//:
//: {
//: some instructions
//: {
//: more instructions
//: }
//: }
//:
//: Braces are just labels, they require no special parsing. The operations
//: 'loop' and 'break' jump to just after the enclosing '{' and '}'
//: respectively.
//:
//: Conditional and unconditional 'loop' and 'break' should give us 80% of the
//: benefits of the control-flow primitives we're used to in other languages,
//: like 'if', 'while', 'for', etc.
:(scenario "brace_conversion")
recipe main [
{
break
1:integer <- copy 0:literal
}
]
+after-brace: recipe main
+after-brace: jump 1:offset
+after-brace: copy ...
//: one-time setup
:(after "int main")
Transform.push_back(transform_braces);
:(code)
void transform_braces(const recipe_number r) {
const int OPEN = 0, CLOSE = 1;
list<pair<int/*OPEN/CLOSE*/, size_t/*step index*/> > braces;
for (size_t index = 0; index < Recipe[r].steps.size(); ++index) {
const instruction& inst = Recipe[r].steps[index];
if (inst.label == "{") {
trace("brace") << r << ": push (open, " << index << ")";
braces.push_back(pair<int,size_t>(OPEN, index));
}
if (inst.label == "}") {
trace("brace") << "push (close, " << index << ")";
braces.push_back(pair<int,size_t>(CLOSE, index));
}
}
stack<size_t/*step index*/> open_braces;
trace("after-brace") << "recipe " << Recipe[r].name;
for (size_t index = 0; index < Recipe[r].steps.size(); ++index) {
instruction& inst = Recipe[r].steps[index];
if (inst.label == "{") open_braces.push(index);
else if (inst.label == "}") open_braces.pop();
else if (inst.operation == Recipe_number["loop"]) {
inst.operation = Recipe_number["jump"];
if (inst.ingredients.size() > 0 && inst.ingredients[0].types[0] == 0) {
// explicit target; a later phase will handle it
;
}
else {
reagent ing(0); // literal
ing.value = open_braces.top()-index;
inst.ingredients.push_back(ing);
trace("after-brace") << "jump " << ing.value << ":offset";
}
}
else if (inst.operation == Recipe_number["break"]) {
inst.operation = Recipe_number["jump"];
if (inst.ingredients.size() > 0 && inst.ingredients[0].types[0] == 0) {
// explicit target; a later phase will handle it
;
}
else {
reagent ing(0); // literal
ing.value = matching_brace(open_braces.top(), braces) - index - 1;
inst.ingredients.push_back(ing);
trace("after-brace") << "jump " << ing.value << ":offset";
}
}
else {
trace("after-brace") << inst.name << " ...";
}
}
}
size_t matching_brace(size_t index, const list<pair<int, size_t> >& braces) {
int stacksize;
for (list<pair<int, size_t> >::const_iterator p = braces.begin(); p != braces.end(); ++p) {
if (p->second < index) continue;
stacksize += (p->first ? 1 : -1);
if (stacksize == 0) return p->second;
}
assert(false);
return -1;
}
:(scenario "loop")
recipe main [
1:integer <- copy 0:literal
2:integer <- copy 0:literal
{
3:integer <- copy 0:literal
loop
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: copy ...
+after-brace: copy ...
+after-brace: jump -2:offset
:(scenario "break_empty_block")
recipe main [
1:integer <- copy 0:literal
{
break
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: jump 0:offset
:(scenario "break_cascading")
recipe main [
1:integer <- copy 0:literal
{
break
}
{
break
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: jump 0:offset
+after-brace: jump 0:offset
:(scenario "break_cascading2")
recipe main [
1:integer <- copy 0:literal
2:integer <- copy 0:literal
{
break
3:integer <- copy 0:literal
}
{
break
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: copy ...
+after-brace: jump 1:offset
+after-brace: copy ...
+after-brace: jump 0:offset
|