如
上一篇文章所說，
Vczh Library++3.0的NativeX語言實現了
計劃的所有泛型語法。讓我們來看一個簡單的例子：我們為類型寫一個Equals函數。我們可以為普通類型，譬如int32寫一個Equals函數。我們有Vector<T>類型，只要T類型擁有一個Equals函數，那么Vector<T>顯然也可以有Equals函數。問題來了，我們在VectorEquals<T>函數里面怎么知道T的Equals函數究竟是那一個呢？在這里我們用concept和instance，其實也就是haskell的type class在C語言上僅有的一種形式，來表達。
首先我們定義一個叫Eq的concept，里面包含Equals和NotEquals兩個函數的原型。這兩個函數規定了參數的類型和返回值類型：
1 concept T : Eq
2 {
3 Equals = function bool(T, T);
4 NotEquals = function bool(T, T);
5 }
其次，我們為int32實現這兩個函數。實現的方法很直接，首先我們寫IntEquals和IntNotEquals兩個函數，其次將int32、Eq和這兩個函數綁定起來：
1 instance int32 : Eq
2 {
3 Equals = IntEquals;
4 NotEquals = IntNotEquals;
5 }
6
7 function bool IntEquals(int32 a, int32 b)
8 (result = (a == b));
9
10 function bool IntNotEquals(int32 a, int32 b)
11 (result = (a != b));
因為綁定在Eq上的T的Equals和NotEquals函數的參數是T，因此IntEquals和IntNotEquals的參數必然就是int32了。接下來我們聲明一個Vector<T>類型，然后實現這兩個函數：
1 generic<U>
2 structure Vector
3 {
4 U X;
5 U Y;
6 }
7
8 generic<V> where
9 V : Eq
10 instance Vector : Eq
11 {
12 Equals = VectorEquals<V>;
13 NotEquals = VectorNotEquals<V>;
14 }
15
16 generic<W> where
17 W : Eq
18 function bool VectorEquals(Vector<W> a, Vector<W> b)
19 {
20 variable bool x_equals = Eq<W>::Equals(a.X, b.X);
21 variable bool y_equals = Eq<W>::Equals(a.Y, b.Y);
22 (result = (x_equals && y_equals));
23 }
24
25 generic<W> where
26 W : Eq
27 function bool VectorNotEquals(Vector<W> a, Vector<W> b)
28 (result = ( ! VectorEquals<W>(a, b)));
我們看得出來這跟普通的函數沒什么區別，而且在給Vector<T>綁定Eq的時候，我們還可以規定T必須也存在一個到Eq的綁定。因此我們不僅可以有Vector<int32>，還能有Vector<Vector<int32>>。而且在VectorEquals內部使用Eq<W>::Equals函數的時候，如果函數聲明沒有where W:Eq的標記那么就無法通過編譯。因此所有調用VectorEquals<W>函數的W都需要有一個到Eq的綁定。如此下去，只要你漏綁定了什么，都會得到編譯錯誤的提示。
最后就剩下main函數了：
1 function int32 main1()
2 {
3 variable Vector<int32> v1;
4 variable Vector<int32> v2;
5 (v1.X = 0s32);
6 (v1.Y = 1s32);
7 (v2.X = 2s32);
8 (v2.Y = 3s32);
9 if(Eq<Vector<int32>>::Equals(v1, v2))
10 (result = 1s32);
11 else
12 (result = 0s32);
13 }
我們可以main函數和VectorEquals函數看到一個Equals函數是如何被調用的。當然這個代碼編譯成二進制代碼之后，虛擬機將會在適當的時候搜索、展開并實例化這些具體的函數。我們可以看看編譯器在執行完這些代碼之后究竟產生了什么數據結構：
1 -----------------------------------------------
2 Loaded Assemblies[0]
3 -----------------------------------------------
4 .data
5 .label
6 .code
7 0: stack_reserve 2
8 1: stack_offset 24
9 2: push s32 0
10 3: add s32
11 4: readmem 4
12 5: stack_offset 16
13 6: push s32 0
14 7: add s32
15 8: readmem 4
16 9: stack_offset -1
17 10: call 46 1
18 11: stack_offset 24
19 12: push s32 4
20 13: add s32
21 14: readmem 4
22 15: stack_offset 16
23 16: push s32 4
24 17: add s32
25 18: readmem 4
26 19: stack_offset -2
27 20: call 46 1
28 21: stack_offset -2
29 22: read u8
30 23: convert u32 u8
31 24: stack_offset -1
32 25: read u8
33 26: convert u32 u8
34 27: and u32
35 28: push u32 0
36 29: ne u32
37 30: resptr
38 31: write u8
39 32: stack_reserve -2
40 33: ret 16
41
42 -----------------------------------------------
43 Loaded Assemblies[1]
44 -----------------------------------------------
45 .data
46 .label
47 0: instruction 3
48 1: instruction 8
49 2: instruction 46
50 3: instruction 56
51 4: instruction 66
52 5: instruction 100
53 .code
54 0: stack_reserve 0
55 1: stack_reserve 0
56 2: ret 0
57 3: stack_reserve 0
58 4: resptr
59 5: call 8 1
60 6: stack_reserve 0
61 7: ret 0
62 8: stack_reserve 16
63 9: push s32 0
64 10: stack_offset -8
65 11: push s32 0
66 12: add s32
67 13: write s32
68 14: push s32 1
69 15: stack_offset -8
70 16: push s32 4
71 17: add s32
72 18: write s32
73 19: push s32 2
74 20: stack_offset -16
75 21: push s32 0
76 22: add s32
77 23: write s32
78 24: push s32 3
79 25: stack_offset -16
80 26: push s32 4
81 27: add s32
82 28: write s32
83 29: stack_reserve 1
84 30: stack_offset -16
85 31: readmem 8
86 32: stack_offset -8
87 33: readmem 8
88 34: stack_top 16
89 35: call 0 0
90 36: jumpfalse 41 1
91 37: push s32 1
92 38: resptr
93 39: write s32
94 40: jump 44 1
95 41: push s32 0
96 42: resptr
97 43: write s32
98 44: stack_reserve -16
99 45: ret 0
100 46: stack_reserve 0
101 47: stack_offset 20
102 48: read s32
103 49: stack_offset 16
104 50: read s32
105 51: eq s32
106 52: resptr
107 53: write u8
108 54: stack_reserve 0
109 55: ret 8
110 56: stack_reserve 0
111 57: stack_offset 20
112 58: read s32
113 59: stack_offset 16
114 60: read s32
115 61: ne s32
116 62: resptr
117 63: write u8
118 64: stack_reserve 0
119 65: ret 8
120 66: stack_reserve 2
121 67: stack_offset 0[Linear]
122 68: push s32 0
123 69: add s32
124 70: readmem 1[Linear]
125 71: stack_offset 16
126 72: push s32 0
127 73: add s32
128 74: readmem 1[Linear]
129 75: stack_offset -1
130 76: generic_instance_callfunc 1
131 77: stack_offset 0[Linear]
132 78: push s32 1[Linear]
133 79: add s32
134 80: readmem 1[Linear]
135 81: stack_offset 16
136 82: push s32 1[Linear]
137 83: add s32
138 84: readmem 1[Linear]
139 85: stack_offset -2
140 86: generic_instance_callfunc 1
141 87: stack_offset -2
142 88: read u8
143 89: convert u32 u8
144 90: stack_offset -1
145 91: read u8
146 92: convert u32 u8
147 93: and u32
148 94: push u32 0
149 95: ne u32
150 96: resptr
151 97: write u8
152 98: stack_reserve -2
153 99: ret 2[Linear]
154 100: stack_reserve 0
155 101: stack_reserve 1
156 102: stack_offset 0[Linear]
157 103: readmem 3[Linear]
158 104: stack_offset 16
159 105: readmem 3[Linear]
160 106: stack_top 2[Linear]
161 107: generic_callfunc 0
162 108: push s8 1
163 109: xor u8
164 110: resptr
165 111: write u8
166 112: stack_reserve 0
167 113: ret 2[Linear]
168 .exports
169 Assembly Name: assembly_generated
170 Exports[0] = (3, main)
171 Exports[1] = (8, main1)
172 Exports[2] = (46, IntEquals)
173 Exports[3] = (56, IntNotEquals)
174 Function Entries[0] = {
175 Name = VectorEquals
176 Arguments = 1
177 Instruction = 66
178 Length = 34
179 UniqueName = [assembly_generated]::[VectorEquals]
180 }
181 Function Entries[1] = {
182 Name = VectorNotEquals
183 Arguments = 1
184 Instruction = 100
185 Length = 14
186 UniqueName = [assembly_generated]::[VectorNotEquals]
187 }
188 Targets[0] = {
189 AssemblyName = assembly_generated
190 SymbolName = VectorEquals
191 Argument[0] = {0} : 1*T0 + 0
192 }
193 Linears[0] = 2*T0 + 16
194 Linears[1] = 1*T0 + 0
195 Linears[2] = 4*T0 + 0
196 Linears[3] = 2*T0 + 0
197 Concepts[0] = {
198 Name = Eq
199 Functions[0] = Equals
200 Functions[1] = NotEquals
201 }
202 Instances[0] = {
203 ConcpetAssemblyName = assembly_generated
204 ConceptSymbolName = Eq
205 TypeUniqueName = s32
206 Arguments = 0
207 Functions[0] = {
208 FunctionName = Equals
209 AssemblyName = assembly_generated
210 SymbolName = IntEquals
211 }
212 Functions[1] = {
213 FunctionName = NotEquals
214 AssemblyName = assembly_generated
215 SymbolName = IntNotEquals
216 }
217 }
218 Instances[1] = {
219 ConcpetAssemblyName = assembly_generated
220 ConceptSymbolName = Eq
221 TypeUniqueName = [assembly_generated]::[Vector]
222 Arguments = 1
223 Functions[0] = {
224 FunctionName = Equals
225 AssemblyName = assembly_generated
226 SymbolName = VectorEquals
227 Argument[0] = {0} : 1*T0 + 0
228 }
229 Functions[1] = {
230 FunctionName = NotEquals
231 AssemblyName = assembly_generated
232 SymbolName = VectorNotEquals
233 Argument[0] = {0} : 1*T0 + 0
234 }
235 }
236 Instance Targets[0] = {
237 AssemblyName = assembly_generated
238 SymbolName = Eq
239 FunctionName = Equals
240 Argument = [assembly_generated]::[Vector] : 8 {
241 s32 : 4
242 }
243 }
244 Instance Targets[1] = {
245 AssemblyName = assembly_generated
246 SymbolName = Eq
247 FunctionName = Equals
248 Argument = {0} : 1*T0 + 0
249 }
250
251 -----------------------------------------------
252 Assembly Name Map
253 -----------------------------------------------
254 assembly_generated = 1
255
256 -----------------------------------------------
257 Function Pointer Map
258 -----------------------------------------------
259 0 = Assemblies[-1].Instructions[-1]
260 1 = Assemblies[1].Instructions[3]
261 2 = Assemblies[1].Instructions[8]
262 3 = Assemblies[1].Instructions[46]
263 4 = Assemblies[1].Instructions[56]
264 5 = Assemblies[1].Instructions[66]
265 6 = Assemblies[1].Instructions[100]
266 7 = Assemblies[0].Instructions[0]
267
268 -----------------------------------------------
269 Loaded Symbol Names
270 -----------------------------------------------
271 assembly_generated.IntEquals
272 assembly_generated.IntNotEquals
273 assembly_generated.main
274 assembly_generated.main1
275
276 -----------------------------------------------
277 Generic Function Entry Map
278 -----------------------------------------------
279 assembly_generated.VectorEquals
280 Instruction = 66
281 Count = 34
282 Assembly = 1
283 Generic Argument Count = 1
284 Unique Entry ID = [assembly_generated]::[VectorEquals]
285 assembly_generated.VectorNotEquals
286 Instruction = 100
287 Count = 14
288 Assembly = 1
289 Generic Argument Count = 1
290 Unique Entry ID = [assembly_generated]::[VectorNotEquals]
291
292 -----------------------------------------------
293 Generic Variable Entry Map
294 -----------------------------------------------
295
296 -----------------------------------------------
297 Instanciated Generic Function Map
298 -----------------------------------------------
299 [assembly_generated]::[VectorEquals]<s32> = 7
300
301 -----------------------------------------------
302 Instanciated Generic Variable Map
303 -----------------------------------------------
304
305 -----------------------------------------------
306 Cached Generic Target List
307 -----------------------------------------------
308 Assembly Name = assembly_generated
309 Symbol Name = VectorEquals
310 Arguments = {
311 Argument[0] = {
312 Name = s32
313 Size = 4
314 }
315 }
316
317 -----------------------------------------------
318 Generic Concept Map
319 -----------------------------------------------
320 assembly_generated.Eq
321
322 -----------------------------------------------
323 Generic Instance Map
324 -----------------------------------------------
325 assembly_generated.Eq<[assembly_generated]::[Vector]>
326 Generic Argument Count = 1
327 Resource Index = 1
328 Function Equals = 0
329 Function NotEquals = 1
330 assembly_generated.Eq<s32>
331 Generic Argument Count = 0
332 Resource Index = 0
333 Function Equals = 0
334 Function NotEquals = 1
335
336
Assembly[0]是專門用來保存模板函數的展開結果的，當然這里面只有一個模板函數被使用了：VectorEquals<int32>。其他的Assembly都是代碼編譯出來的。
接下來只需要測試一下，然后就可以著手開發最后一個語法了：異常處理。
posted on 2010-08-26 03:09
陳梓瀚(vczh) 閱讀(3129)
評論(3) 編輯 收藏 引用 所屬分類:
VL++3.0開發紀事