编译器实践一之加法栈式计算机

下面是一个简单的小型加法栈式计算机

#include <stdio.h>#include <stdlib.h>///////////////////////////////////////////////// Data structures for the Sum language.enum Exp_Kind_t {EXP_INT, EXP_SUM};struct Exp_t{ enum Exp_Kind_t kind;};struct Exp_Int{ enum Exp_Kind_t kind; int i;};struct Exp_Sum{ enum Exp_Kind_t kind; struct Exp_t *left; struct Exp_t *right;};// "constructors"struct Exp_t *Exp_Int_new (int i){ struct Exp_Int *p = (Exp_Int *)malloc (sizeof(Exp_Int)); p->kind = EXP_INT; p->i = i; return (struct Exp_t *)p;}struct Exp_t *Exp_Sum_new (struct Exp_t *left, struct Exp_t *right){ struct Exp_Sum *p = (Exp_Sum *) malloc (sizeof(Exp_Sum)); p->kind = EXP_SUM; p->left = left; p->right = right; return (struct Exp_t *)p;}// "printer"void Exp_print (struct Exp_t *exp){ switch (exp->kind){ case EXP_INT:{struct Exp_Int *p = (struct Exp_Int *)exp;printf ("%d", p->i);break; } case EXP_SUM:{struct Exp_Sum *p = (struct Exp_Sum *)exp;Exp_print (p->left);printf ("+");Exp_print (p->right);break; } default:break; }}//////////////////////////////////////////////// Data structures for the Stack language.enum Stack_Kind_t {STACK_ADD, STACK_PUSH};struct Stack_t{ enum Stack_Kind_t kind;};struct Stack_Add{ enum Stack_Kind_t kind;};struct Stack_Push{ enum Stack_Kind_t kind; int i;};// "constructors"struct Stack_t *Stack_Add_new (){ struct Stack_Add *p = (Stack_Add *)malloc (sizeof(Stack_Add)); p->kind = STACK_ADD; return (struct Stack_t *)p;}struct Stack_t *Stack_Push_new (int i){ struct Stack_Push *p = (Stack_Push *)malloc (sizeof(Stack_Push)); p->kind = STACK_PUSH; p->i = i; return (struct Stack_t *)p;}/// instruction liststruct List_t{ struct Stack_t *instr; struct List_t *next;};struct List_t *List_new (struct Stack_t *instr, struct List_t *next){ struct List_t *p = (List_t *)malloc (sizeof (List_t)); p->instr = instr; p->next = next; return p;}// "printer"void List_reverse_print (struct List_t *list){if(list == NULL)return ;List_reverse_print(list->next) ;if(list->instr->kind == STACK_PUSH){printf("PUSH %d\n",((Stack_Push *)(list->instr))->i) ;}else{puts("ADD") ;}}//////////////////////////////////////////////////// a compiler from Sum to Stackstruct List_t *all = 0;void emit (struct Stack_t *instr){ all = List_new (instr, all);}void compile (struct Exp_t *exp){ switch (exp->kind){ case EXP_INT:{struct Exp_Int *p = (struct Exp_Int *)exp;emit (Stack_Push_new (p->i));break; } case EXP_SUM:{// TODO();Exp_Sum * t = (Exp_Sum *)exp ;compile(t->left) ;compile(t->right) ;emit(Stack_Add_new()) ;break; } default:break; }}//////////////////////////////////////////////////// program entryint main(){ printf("Compile starting\n"); // build an expression tree: //+ /// \ //+ 4 /// \ //2 3 struct Exp_t *exp = Exp_Sum_new (Exp_Sum_new(Exp_Int_new (2), Exp_Int_new (3)), Exp_Int_new (4)); //Exp_Sum_new(Exp_Int_new(4),NULL) ; // print out this tree: printf ("the expression is:\n"); Exp_Sum *p = (Exp_Sum *) exp ; if(p->left == NULL) { printf("%d\n",((Exp_Int *)(p->right))->i) ; printf("PUSH %d\n",((Exp_Int *)(p->right))->i) ; } else if(p->right == NULL) { printf("%d\n",((Exp_Int *)(p->left))->i) ; printf("PUSH %d\n",((Exp_Int *)(p->left))->i) ; } else {Exp_print (exp);// compile this tree to Stack machine instructionsputs("") ;compile (exp);// print out the generated Stack instructons:List_reverse_print (all); }printf("\nCompile finished\n"); return 0;}

，思念带着一种默默地忧伤，

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