📄 unit1.cpp
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if (SYM==ODDSYM) { GetSym(); EXPRESSION(FSYS,LEV,TX); GEN(OPR,0,6); }
else {
EXPRESSION(SymSetUnion(SymSetNew(EQL,NEQ,LSS,LEQ,GTR,GEQ),FSYS),LEV,TX);
if (!SymIn(SYM,SymSetNew(EQL,NEQ,LSS,LEQ,GTR,GEQ))) Error(20);
else {
RELOP=SYM; GetSym(); EXPRESSION(FSYS,LEV,TX);
switch (RELOP) {
case EQL: GEN(OPR,0,8); break;
case NEQ: GEN(OPR,0,9); break;
case LSS: GEN(OPR,0,10); break;
case GEQ: GEN(OPR,0,11); break;
case GTR: GEN(OPR,0,12); break;
case LEQ: GEN(OPR,0,13); break;
}
}
}
} /*CONDITION*/
//---------------------------------------------------------------------------
void STATEMENT(SYMSET FSYS,int LEV,int &TX) { /*STATEMENT*/
int i,CX1,CX2;
SYMBOL SET;
switch (SYM) {
case IDENT:
i=POSITION(ID,TX);
if (i==0) Error(11);
else
if (TABLE[i].KIND!=VARIABLE) { /*ASSIGNMENT TO NON-VARIABLE*/
Error(12); i=0;
}
GetSym();
if (SYM==BECOMES){ GetSym();
EXPRESSION(FSYS,LEV,TX);
}
else if(SYM==PLUSEQL) {GetSym(); //处理'+='
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR); //将+=前面的变量的值放在栈顶
EXPRESSION(FSYS,LEV,TX);
GEN(OPR,0,2); //将栈顶和次栈顶两数相加
}
else if(SYM==MINUSEQL) //处理单词'-='
{GetSym();
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
EXPRESSION(FSYS,LEV,TX);
GEN(OPR,0,3); //将栈顶和次栈顶两数相减
}
else if(SYM==DPLUS) //处理单词'++'
{GetSym();
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
GEN(LIT,0,1); //栈顶置1
GEN(OPR,0,2); //将栈顶和次栈顶两数相加
}
else if(SYM==DMINUS) //处理单词'--'
{GetSym();
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
GEN(LIT,0,-1); //栈顶置-1
GEN(OPR,0,2); //将栈顶和次栈顶两数相减
}
else Error(13);
if (i!=0) GEN(STO,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
break;
case READSYM:
GetSym();
if (SYM!=LPAREN) Error(34);
else
do {
GetSym();
if (SYM==IDENT) i=POSITION(ID,TX);
else i=0;
if (i==0) Error(35);
else {
GEN(OPR,0,16);
GEN(STO,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
}
GetSym();
}while(SYM==COMMA);
if (SYM!=RPAREN) {
Error(33);
while (!SymIn(SYM,FSYS)) GetSym();
}
else GetSym();
break; /* READSYM */
case WRITESYM:
GetSym();
if (SYM==LPAREN) {
do {
GetSym();
EXPRESSION(SymSetUnion(SymSetNew(RPAREN,COMMA),FSYS),LEV,TX);
GEN(OPR,0,14);
}while(SYM==COMMA);
if (SYM!=RPAREN) Error(33);
else GetSym();
}
GEN(OPR,0,15);
break; /*WRITESYM*/
case CALLSYM:
GetSym();
if (SYM!=IDENT) Error(14);
else {
i=POSITION(ID,TX);
if (i==0) Error(11);
else
if (TABLE[i].KIND==PROCEDUR)
GEN(CAL,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
else Error(15);
GetSym();
}
break;
case IFSYM:
GetSym();
CONDITION(SymSetUnion(SymSetNew(THENSYM,DOSYM),FSYS),LEV,TX);
if (SYM==THENSYM) GetSym();
else Error(16);
CX1=CX; GEN(JPC,0,0); //产生一新目标代码 ，用于条件为假时跳到执行假语句
STATEMENT(SymSetAdd(ELSESYM,FSYS),LEV,TX); //条件为真时处理语句
if(SYM==ELSESYM) // 判断后面是else的情况
{
CX2=CX; //保存下条目标代码的位置
GEN(JMP,0,0); //产生一新目标代码 ，用于执行完真语句后跳出if语句
CODE[CX1].A=CX; // 填充CX1的地址 ，即使条件语句的假入口
GetSym();
STATEMENT(SymSetAdd(ELSESYM,FSYS),LEV,TX); //执行假语句
CODE[CX2].A=CX; //回填 CX2，即整个if语句的出口
}
else
CODE[CX1].A=CX;
break;
case BEGINSYM:
GetSym();
STATEMENT(SymSetUnion(SymSetNew(SEMICOLON,ENDSYM),FSYS),LEV,TX);
while (SymIn(SYM, SymSetAdd(SEMICOLON,STATBEGSYS))) {
if (SYM==SEMICOLON) GetSym();
else Error(10);
STATEMENT(SymSetUnion(SymSetNew(SEMICOLON,ENDSYM),FSYS),LEV,TX);
}
if (SYM==ENDSYM) GetSym();
else Error(17);
break;
case WHILESYM:
CX1=CX; GetSym(); CONDITION(SymSetAdd(DOSYM,FSYS),LEV,TX);
CX2=CX; GEN(JPC,0,0);
if (SYM==DOSYM) GetSym();
else Error(18);
STATEMENT(FSYS,LEV,TX);
GEN(JMP,0,CX1);
CODE[CX2].A=CX;
break;
case FORSYM:
GetSym();
if(SYM!=IDENT) Error(8);
else
{i=POSITION(ID,TX); /*取得i在符号表的位置；若存在则判断是否为变量*/
if(i==0) Error(11);
else if(TABLE[i].KIND!=VARIABLE) {
Error(12); i=0;}
else{
GetSym();
if(SYM==BECOMES)GetSym();
else Error(13);
EXPRESSION(SymSetUnion(SymSetNew(TOSYM,DOWNTOSYM),FSYS),LEV,TX);
if(i!=0) GEN(STO,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
if(SYM==TOSYM||SYM==DOWNTOSYM){
SET=SYM; //保存当前保留字，用于后面操作的选择
CX1=CX; //保留当前指令地址
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
GetSym();}
else Error(8);
EXPRESSION(SymSetAdd(DOSYM,FSYS),LEV,TX);
if(SET==TOSYM) GEN(OPR,0,13); //次栈顶是否小于等于栈顶
else GEN(OPR,0,11); //次栈顶是否大于等于栈顶
CX2=CX;GEN(JPC,0,0); //产生一新目标代码 ，用于条件为假时跳到执行假语句
if(SYM==DOSYM) GetSym();
else Error(18);
STATEMENT(FSYS,LEV,TX); //执行DOS后面语句
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR );
GEN(LIT,0,1); //将常量值1取到运行栈顶
if(SET==TOSYM) GEN(OPR,0,2); //次栈顶与栈顶相加,即加1
else GEN(OPR,0,3); //次栈顶与栈顶相减,即减1
if(i!=0)GEN(STO,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
GEN(JMP,0,CX1); //转回CX1处
CODE[CX2].A=CX;
}
}
break;
}
TEST(FSYS,SymSetNULL(),19);
} /*STATEMENT*/
//---------------------------------------------------------------------------
void Block(int LEV, int TX, SYMSET FSYS) {
int DX=3; /*DATA ALLOCATION INDEX*/
int TX0=TX; /*INITIAL TABLE INDEX*/
int CX0=CX; /*INITIAL CODE INDEX*/
TABLE[TX].vp.ADR=CX; GEN(JMP,0,0);
if (LEV>LEVMAX) Error(32);
do {
if (SYM==CONSTSYM) {
GetSym();
do {
ConstDeclaration(LEV,TX,DX);
while (SYM==COMMA) {
GetSym(); ConstDeclaration(LEV,TX,DX);
}
if (SYM==SEMICOLON) GetSym();
else Error(5);
}while(SYM==IDENT);
}
if (SYM==VARSYM) {
GetSym();
do {
VarDeclaration(LEV,TX,DX);
while (SYM==COMMA) { GetSym(); VarDeclaration(LEV,TX,DX); }
if (SYM==SEMICOLON) GetSym();
else Error(5);
}while(SYM==IDENT);
}
while ( SYM==PROCSYM) {
GetSym();
if (SYM==IDENT) { ENTER(PROCEDUR,LEV,TX,DX); GetSym(); }
else Error(4);
if (SYM==SEMICOLON) GetSym();
else Error(5);
Block(LEV+1,TX,SymSetAdd(SEMICOLON,FSYS));
if (SYM==SEMICOLON) {
GetSym();
TEST(SymSetUnion(SymSetNew(IDENT,PROCSYM),STATBEGSYS),FSYS,6);
}
else Error(5);
}
TEST(SymSetAdd(IDENT,STATBEGSYS), DECLBEGSYS,7);
}while(SymIn(SYM,DECLBEGSYS));
CODE[TABLE[TX0].vp.ADR].A=CX;
TABLE[TX0].vp.ADR=CX; /*START ADDR OF CODE*/
TABLE[TX0].vp.SIZE=DX; /*SIZE OF DATA SEGMENT*/
GEN(INI,0,DX);
STATEMENT(SymSetUnion(SymSetNew(SEMICOLON,ENDSYM),FSYS),LEV,TX);
GEN(OPR,0,0); /*RETURN*/
TEST(FSYS,SymSetNULL(),8);
ListCode(CX0);
} /*Block*/
//---------------------------------------------------------------------------
int BASE(int L,int B,int S[]) {
int B1=B; /*FIND BASE L LEVELS DOWN*/
while (L>0) { B1=S[B1]; L=L-1; }
return B1;
} /*BASE*/
//---------------------------------------------------------------------------
void Interpret() {
const STACKSIZE = 500;
int P,B,T; /*PROGRAM BASE TOPSTACK REGISTERS*/
INSTRUCTION I;
int S[STACKSIZE]; /*DATASTORE*/
Form1->printfs("~~~ RUN PL0 ~~~");
fprintf(FOUT,"~~~ RUN PL0 ~~~\n");
T=0; B=1; P=0;
S[1]=0; S[2]=0; S[3]=0;
do {
I=CODE[P]; P=P+1;
switch (I.F) {
case LIT: T++; S[T]=I.A; break;
case OPR:
switch (I.A) { /*OPERATOR*/
case 0: /*RETURN*/ T=B-1; P=S[T+3]; B=S[T+2]; break;
case 1: S[T]=-S[T]; break;
case 2: T--; S[T]=S[T]+S[T+1]; break;
case 3: T--; S[T]=S[T]-S[T+1]; break;
case 4: T--; S[T]=S[T]*S[T+1]; break;
case 5: T--; S[T]=S[T] % S[T+1]; break;
case 6: S[T]=(S[T]%2!=0); break;
case 8: T--; S[T]=S[T]==S[T+1]; break;
case 9: T--; S[T]=S[T]!=S[T+1]; break;
case 10: T--; S[T]=S[T]<S[T+1]; break;
case 11: T--; S[T]=S[T]>=S[T+1]; break;
case 12: T--; S[T]=S[T]>S[T+1]; break;
case 13: T--; S[T]=S[T]<=S[T+1]; break;
case 14: Form1->printls("",S[T]); fprintf(FOUT,"%d\n",S[T]); T--;
break;
case 15: /*Form1->printfs(""); fprintf(FOUT,"\n"); */ break;
case 16: T++; S[T]=InputBox("输入","请键盘输入：", 0).ToInt();
Form1->printls("? ",S[T]); fprintf(FOUT,"? %d\n",S[T]);
break;
}
break;
case LOD: T++; S[T]=S[BASE(I.L,B,S)+I.A]; break;
case STO: S[BASE(I.L,B,S)+I.A]=S[T]; T--; break;
case CAL: /*GENERAT NEW Block MARK*/
S[T+1]=BASE(I.L,B,S); S[T+2]=B; S[T+3]=P;
B=T+1; P=I.A; break;
case INI: T=T+I.A; break;
case JMP: P=I.A; break;
case JPC: if (S[T]==0) P=I.A; T--; break;
} /*switch*/
}while(P!=0);
Form1->printfs("~~~ END PL0 ~~~");
fprintf(FOUT,"~~~ END PL0 ~~~\n");
} /*Interpret*/
//---------------------------------------------------------------------------
void __fastcall TForm1::ButtonRunClick(TObject *Sender) {
for (CH=' '; CH<='^'; CH++) SSYM[CH]=NUL;
strcpy(KWORD[ 1],"BEGIN"); strcpy(KWORD[ 2],"CALL");
strcpy(KWORD[ 3],"CONST"); strcpy(KWORD[ 4],"DO");
strcpy(KWORD[ 5],"DOWNTO"); strcpy(KWORD[ 6],"ELSE");
strcpy(KWORD[ 7],"END"); strcpy(KWORD[ 8],"FOR");
strcpy(KWORD[ 9],"IF"); strcpy(KWORD[10],"ODD");
strcpy(KWORD[11],"PROCEDURE"); strcpy(KWORD[12],"PROGRAM");
strcpy(KWORD[13],"READ"); strcpy(KWORD[14],"THEN");
strcpy(KWORD[15],"TO"); strcpy(KWORD[16],"VAR");
strcpy(KWORD[17],"WHILE"); strcpy(KWORD[18],"WRITE");
WSYM[ 1]=BEGINSYM; WSYM[ 2]=CALLSYM;
WSYM[ 3]=CONSTSYM; WSYM[ 4]=DOSYM;
WSYM[ 5]=DOWNTOSYM; WSYM[ 6]=ELSESYM;
WSYM[ 7]=ENDSYM; WSYM[ 8]=FORSYM;
WSYM[ 9]=IFSYM; WSYM[10]=ODDSYM;
WSYM[11]=PROCSYM; WSYM[12]=PROGSYM;
WSYM[13]=READSYM; WSYM[14]=THENSYM;
WSYM[15]=TOSYM; WSYM[16]=VARSYM;
WSYM[17]=WHILESYM; WSYM[18]=WRITESYM;
SSYM['+']=PLUS; SSYM['-']=MINUS;
SSYM['*']=TIMES; SSYM['/']=SLASH;
SSYM['(']=LPAREN; SSYM[')']=RPAREN;
SSYM['=']=EQL; SSYM[',']=COMMA;
SSYM['.']=PERIOD; SSYM['#']=NEQ;
SSYM[';']=SEMICOLON;
strcpy(MNEMONIC[LIT],"LIT"); strcpy(MNEMONIC[OPR],"OPR");
strcpy(MNEMONIC[LOD],"LOD"); strcpy(MNEMONIC[STO],"STO");
strcpy(MNEMONIC[CAL],"CAL"); strcpy(MNEMONIC[INI],"INI");
strcpy(MNEMONIC[JMP],"JMP"); strcpy(MNEMONIC[JPC],"JPC");
DECLBEGSYS=(int*)malloc(sizeof(int)*41);
STATBEGSYS=(int*)malloc(sizeof(int)*41);
FACBEGSYS =(int*)malloc(sizeof(int)*41);
for(int j=0; j<41; j++) {
DECLBEGSYS[j]=0; STATBEGSYS[j]=0; FACBEGSYS[j] =0;
}
DECLBEGSYS[CONSTSYM]=1;
DECLBEGSYS[VARSYM]=1;
DECLBEGSYS[PROCSYM]=1;
STATBEGSYS[BEGINSYM]=1;
STATBEGSYS[CALLSYM]=1;
STATBEGSYS[IFSYM]=1;
STATBEGSYS[WHILESYM]=1;
STATBEGSYS[WRITESYM]=1;
FACBEGSYS[IDENT] =1;
FACBEGSYS[NUMBER]=1;
FACBEGSYS[LPAREN]=1;
if ((FIN=fopen((Form1->EditName->Text+".PL0").c_str(),"r"))!=0) {
FOUT=fopen((Form1->EditName->Text+".COD").c_str(),"w");
Form1->printfs("=== COMPILE PL0 ===");
fprintf(FOUT,"=== COMPILE PL0 ===\n");
ERR=0;
CC=0; CX=0; LL=0; CH=' '; GetSym();
if (SYM!=PROGSYM) Error(0);
else {
GetSym();
if (SYM!=IDENT) Error(0);
else {
GetSym();
if (SYM!=SEMICOLON) Error(5);
else GetSym();
}
}
Block(0,0,SymSetAdd(PERIOD,SymSetUnion(DECLBEGSYS,STATBEGSYS)));
if (SYM!=PERIOD) Error(9);
if (ERR==0) Interpret();
else {
Form1->printfs("ERROR IN PL/0 PROGRAM");
fprintf(FOUT,"ERROR IN PL/0 PROGRAM");
}
fprintf(FOUT,"\n"); fclose(FOUT);
}
}
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