📄 parse.cpp
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if(lookahead==EOF)
{
error(32,line);
cout<<progname<<".obj- "<<errorcount<<" error(s)"<<endl;
exit(0);
}
}
}
}
//<if语句>:
void if_sent(){//<if语句> -> if<表达式>then <语句)[eIse <语句>]
int vartype;
int oldp1,oldp2,newp,offs;
streampos VarPt1,VarPt2,temp;
match(If);
int lineno=LINE;
express(vartype);//<表达式> vartype获得变量类型
if(vartype!=Boolean){
error(6,lineno);
// return;
}
match(Then);
oldp1=pfollow;//
// outfile<<"dox";
outfile<<5<<' ';
VarPt1=outfile.tellp();
pfollow+=2;
outfile<<" "<<endl;
sentence();//<语句>
if(lookahead==Else){
match(Else);
oldp2=pfollow;
// outfile<<"gotox";
outfile<<12<<' ';
VarPt2=outfile.tellp();
pfollow+=2;
outfile<<" "<<endl;
//backpatch
newp=pfollow;
offs=newp-oldp1;
temp=outfile.tellp();
outfile.seekp(VarPt1);
// outfile<<"("<<offs<<");";
outfile<<offs;
outfile.seekp(temp);
sentence();//<语句2>
newp=pfollow;
offs=newp-oldp2;
temp=outfile.tellp();
outfile.seekp(VarPt2);
outfile<<offs;
// outfile<<"("<<offs<<");";
outfile.seekp(temp);
}
else{
newp=pfollow;
offs=newp-oldp1;
temp=outfile.tellp();
outfile.seekp(VarPt1);
outfile<<offs;
// outfile<<"("<<offs<<");";
outfile.seekp(temp);
}
}
//<while语句>:
void while_sent(){//<while<语句> -> while<表达式> do<语句>
int vartype;
int oldp1,oldp2,offs;
streampos VarPt,temp;
match(While);//
int lineno=LINE;
oldp1=pfollow;
express(vartype);
if(vartype!=Boolean){
error(6,lineno);
}
match(Do); //
oldp2=pfollow;
outfile<<5<<' ';// outfile<<"dox";
pfollow+=2;
VarPt=outfile.tellp();//
outfile<<" "<<endl;
sentence();//<语句2>
offs=oldp1-pfollow;//
outfile<<12<<' '<<offs<<endl;// outfile<<"gotox("<<offs<<");"<<endl;
pfollow+=2;
offs=pfollow-oldp2;
temp=outfile.tellp();
outfile.seekp(VarPt);
outfile<<offs;//backpatch "dox"
outfile.seekp(temp);
}
//<复合语句>:
void com_sent(){//<复合语句> -> begin <语句>{；<语句>}end
match(Begin);
sentence();
while(lookahead==semicolon){//一个或多个
match(semicolon);
sentence();
}
match(End);
}
//------------------------- read -------------------------
//------------------------- read -------------------------
//<读变量>
void readvar(){
int vartype;
int lineno=LINE;
varaccess(vartype,1);
if(vartype==Boolean){
error(7,lineno);//不能读入到bool类型变量
// return;
}
outfile<<26<<endl;// outfile<<"readx;"<<endl;
pfollow++;
}
//------------------------- write -------------------------
//<写变量>
void writevar(){
int vartype;
express(vartype);
if(vartype==Boolean)
outfile<<32<<endl; // outfile<<"writebooleanx;"<<endl;
else
outfile<<31<<endl; // outfile<<"writeintx;"<<endl;
pfollow++;
}
//<表达式>:
void express(int& VarType){ //<表达式>-> <简单表达式>[<关系算符><简单表达式>]
int opcode;
int vartype1,vartype2;
simple_expr(vartype1);
VarType=vartype1;//2:bool;3:int
int lineno=LINE;
if(isrelational_op(lookahead))
{
opcode=lookahead;
match(lookahead);//向前走一步
simple_expr(vartype2);//
if(vartype1!=vartype2)
{
error(16,lineno);//
return;
}
switch(opcode)
{
case relop_LT://<
// outfile<<"less;"<<endl;
outfile<<14<<endl;
break;
case relop_LE://<=
// outfile<<"notgreater;"<<endl;
outfile<<19<<endl;
break;
case relop_EQ://=
// outfile<<"equal;"<<endl;
outfile<<9<<endl;
break;
case relop_NE://<>
// outfile<<"notequal;"<<endl;
outfile<<18<<endl;
break;
case relop_GT://>
// outfile<<"greater;"<<endl;
outfile<<11<<endl;
break;
case relop_GE://>=
// outfile<<"notless;"<<endl;
outfile<<20<<endl;
}//switch
pfollow++;
VarType=Boolean;
}//if
}
//<简单表达式>:
void simple_expr(int& VarType){//<简单表达式> -> [+|-]<项>{<加法算符><项>}
int not=0,opcode;
int vartype1,vartype2;
if(lookahead==plus_op){//+
not=-1;
match(plus_op);
}
if(lookahead==minus_op)
{
not=1;
match(minus_op);}
/*
if(lookahead==minus_op){//-
not=1;
// outfile<<"constant(0);"<<endl;
outfile<<3<<' '<<0<<endl;
pfollow+=2;
match(minus_op);
}*/
int lineno=LINE;
term(vartype1);
if(not==1)
{
outfile<<15<<endl;//outfile<<minus()<<endl;
pfollow++;
}
//项
// if(not==1){//negtive：取反
// outfile<<"subtract;"<<endl;
// outfile<<27<<endl;
// pfollow++;
//}
VarType=vartype1;//如果出错，就按照第一个变量的类型继续
if(vartype1==Boolean){//bool
if(not!=0){
error(11,lineno);
// return;
}
while(lookahead==Or){//可能有多个
match(Or);
term(vartype2);//<项>
if(vartype2!=Boolean){
error(13,lineno);//or只能对bool类型变量进行运算
// return;
}
// outfile<<"orx;"<<endl;
outfile<<22<<endl;
pfollow++;
}
if((lookahead==plus_op)||(lookahead==minus_op)){
error(12,LINE);
match(lookahead);
express(vartype2);
}
return;
}
//integer
while((lookahead==plus_op)||(lookahead==minus_op)){//<加法算符> ->+|-|or
opcode=lookahead;
match(lookahead);
term(vartype2);
if(vartype2!=Integer){
error(12,lineno);//加法算符两边必须都为整型
// return;
}
// VarType=Integer;
switch(opcode){
case minus_op://-
// outfile<<"subtract;"<<endl;
outfile<<27<<endl;
break;
case plus_op://+
// outfile<<"add;"<<endl;
outfile<<0<<endl;
}
pfollow++;
}//while
if(lookahead==Or){
error(13,LINE);
match(Or);
express(vartype2);
}
}
//<项>:
void term(int& VarType){// <项> -> <因子>{<乘法算符><因子>}
int opcode;
int vartype1,vartype2;
int lineno=LINE;
gene(vartype1);//因子
VarType=vartype1;
if(vartype1==2){//bool , const of bool
while(lookahead==And){
match(And);
gene(vartype2);//<因子>
if(vartype2!=2){
error(13,lineno);//bool运算不匹配
// return;
}
// outfile<<"andx;"<<endl;
outfile<<1<<endl;
pfollow++;
}
VarType=Boolean;
if((lookahead==multi_op)||(lookahead==Div)||(lookahead==Mod))
{// <乘法算将> -> *|div|mod
error(14,LINE);
match(lookahead);
express(vartype2);
}
return;
}
while((lookahead==multi_op)||(lookahead==Div)||(lookahead==Mod))
{// <乘法算将> -> *|div|mod|and
opcode=lookahead;
match(lookahead);
gene(vartype2);
if(vartype2!=vartype1){
error(14,lineno);//乘法算符两边应该类型相等
// return;
}
switch(opcode){
case multi_op:
// outfile<<"multiply;"<<endl;
outfile<<17<<endl;
break;
case Div:
outfile<<4<<endl;
// outfile<<"divide;"<<endl;
break;
case Mod:
// outfile<<"modulo;"<<endl;
outfile<<16<<endl;
}
VarType=vartype1;
pfollow++;
}//while
if(lookahead==And){
error(13,LINE);
match(And);
express(vartype2);
}
}
//<因子>:
void gene(int& VarType){ // <因子> -> <常数>|<变量访问>|(<表达式>)|not<因子>
int consttype;
int lineno;
if(lookahead==Not){
match(Not);
lineno=LINE;
gene(VarType);//<因子>
if(VarType!=2){
error(13,lineno);//not应该针对bool对象运算
return;
}
// outfile<<"notx;"<<endl;
outfile<<21<<endl;
pfollow++;
}
else if(lookahead==lpar){
match(lpar);
express(VarType);//<表达式>
match(rpar);
}
else if(isconst(consttype)){//<常数>
//push ConstVal:the Const or Number to Stack
VarType=consttype+2;//1:(int) const
// outfile<<"constant("<<ConstVal<<");"<<endl;
outfile<<3<<' '<<ConstVal<<endl;
pfollow+=2;
}
else{
varaccess(VarType,1);//1:不允许访问新类型
// outfile<<"value("<<typelist[VarType].bandwidth<<");"<<endl;
// outfile<<"value(1);"<<endl;
outfile<<28<<' '<<1<<endl;
pfollow+=2;
}
}
//<变量访问>:
void varaccess(int& VisitType,int property)
{//取变量于栈顶操作在search中完成，把匹配的变量名都match
//property=0:只访问新类型；1：只访问bool,integer;
int level,offs,mark,type;
var_list* var=new var_list;
proc_list* proc=new proc_list;
type_list* mother=new type_list;
field_table* child=new field_table;
//检查token类型 0：procedure，1：变量
if(search(token,proc,var)!=1){//不是变量
error(8,LINE);
match(lookahead);
return;
}
int lineno=LINE;
match(lookahead);//
VisitType=var->type;
level=(cur_proc->level)-(proc->level);
offs=var->offset;
//if offs<0:parameter
type=var->type;
mark=type;
//property=1：不允许新类型
if(type>3){//新类型
mother=&typelist[type];//
type=typelist[mark].type;//访问变量的类型:const\int\bool\new type
// VisitType=type;
if((offs<0)&&(var->ConstVal==2))//parameter,引用
outfile<<30<<' '<<level<<' '<<offs<<endl;//outfile<<"Varparam("<<level<<","<<offs<<");"<<endl;
else
outfile<<29<<' '<<level<<' '<<offs<<endl; //outfile<<"Variable("<<level<<","<<offs<<");"<<endl;//
pfollow+=3;
}
while(1){
switch(type){
case Const://type=1
error(15,lineno);//非法使用常量
return;
case Integer://type=2,3
case Boolean:
if(property==0){//只能访问新类型
error(16,lineno);
return;
}
if((offs<0)&&(var->ConstVal==2))//parameter,引用
outfile<<30<<' '<<level<<' '<<offs<<endl;
// outfile<<"Varparam("<<level<<","<<offs<<");"<<endl;
else
outfile<<29<<' '<<level<<' '<<offs<<endl;
// outfile<<"Variable("<<level<<","<<offs<<");"<<endl;
pfollow+=3;
return;
case Array:
if(lookahead!=lbracket){
if(property==1){//错误访问新类型
error(16,lineno);
}
return;//变量访问完毕！
}
match(lbracket);//数组访问
express(VisitType);//把value push
//然后需要做value*数组元素的字节长度，求出offs
//......
if(VisitType==Boolean){//下标不能为boolean类型
error(22,LINE);
// return;
}
// outfile<<"Index("<<typelist[mark].lower<<","<<typelist[mark].upper<<","<<typelist[mark].bandwidthOfelement<<","<<LINE<<");"<<endl;
outfile<<13<<' '<<typelist[mark].lower<<' '<<typelist[mark].upper<<' '<<typelist[mark].bandwidthOfelement<<' '<<LINE<<endl;
pfollow+=5;
match(rbracket);
VisitType=typelist[mark].typeofelement;//
if((VisitType>=1)&&(VisitType<=3)){//在循环中，不会再进入到前面的分支中。在此处已经返回
return;
}
mark=VisitType;//int，bool，or newtype在typelist中的序号,在这目标，visittype&mark一直相等
type=typelist[mark].type;//元素的类型
mother=&typelist[mark];//下一个元素所在的表项
break;
case Record:
if(lookahead!=dot){
if((property==1)&&(VisitType>3)){//错误访问新类型
error(16,lineno);
return;
}
return;
}
match(dot);
if(!searchfield(token,mother,child)){//type_list* mother
error(17,lineno);
match(id);
return;
}
match(id);
// outfile<<"field("<<child->offset<<");"<<endl;
outfile<<10<<' '<<child->offset<<endl;
pfollow+=2;
VisitType=child->type;//访问变量的类型
if((VisitType>=1)&&(VisitType<=3)){
return;
}
mark=child->type;
type=typelist[mark].type;//元素的类型
mother=&typelist[mark]; //下一个元素所在的表项
break;
default:
error(-1,LINE);//undefined error
}//switch
}//while
}
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