📄 unit1.cpp
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/*** PL0 COMPILER WITH CODE GENERATION ***/
//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop
#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
const AL = 10; /* LENGTH OF IDENTIFIERS */
const NORW = 18; /* # OF RESERVED WORDS */
const TXMAX = 100; /* LENGTH OF IDENTIFIER TABLE */
const NMAX = 14; /* MAX NUMBER OF DEGITS IN NUMBERS */
const AMAX =2047; /* MAXIMUM ADDRESS */
const LEVMAX= 3; /* MAX DEPTH OF BLOCK NESTING */
const CXMAX = 200; /* SIZE OF CODE ARRAY */
typedef enum { NUL, IDENT, NUMBER, PLUS, MINUS, TIMES,
SLASH, ODDSYM, EQL, NEQ, LSS, LEQ, GTR, GEQ,
PEQ,MEQ , INC,DEC,
LPAREN, RPAREN, COMMA, SEMICOLON, PERIOD,
BECOMES, BEGINSYM, ELSESYM, ENDSYM, IFSYM, THENSYM,
WHILESYM, WRITESYM, READSYM, DOSYM, CALLSYM,
CONSTSYM, VARSYM, PROCSYM, PROGSYM,
FORSYM,TOSYM,DOWNTOSYM
} SYMBOL;
char *SYMOUT[] = {"NUL", "IDENT", "NUMBER", "PLUS", "MINUS", "TIMES",
"SLASH", "ODDSYM", "EQL", "NEQ", "LSS", "LEQ", "GTR", "GEQ",
"PEQ", "MEQ", "INC","DEC", "LPAREN", "RPAREN", "COMMA", "SEMICOLON", "PERIOD",
"BECOMES", "BEGINSYM", "ELSESYM", "ENDSYM", "IFSYM", "THENSYM",
"WHILESYM", "WRITESYM", "READSYM", "DOSYM", "CALLSYM",
"CONSTSYM", "VARSYM", "PROCSYM", "PROGSYM",
"FORSYM", "TOSYM", "DOWNTOSYM"};
typedef int *SYMSET; // SET OF SYMBOL;
typedef char ALFA[11];
typedef enum { CONSTANT, VARIABLE, PROCEDUR } OBJECTS ;
typedef enum { LIT, OPR, LOD, STO, CAL, INI, JMP, JPC } FCT;
typedef struct {
FCT F; /*FUNCTION CODE*/
int L; /*0..LEVMAX LEVEL*/
int A; /*0..AMAX DISPLACEMENT ADDR*/
} INSTRUCTION;
/* LIT O A -- LOAD CONSTANT A */
/* OPR 0 A -- EXECUTE OPR A */
/* LOD L A -- LOAD VARIABLE L,A */
/* STO L A -- STORE VARIABLE L,A */
/* CAL L A -- CALL PROCEDURE A AT LEVEL L */
/* INI 0 A -- INCREMET T-REGISTER BY A */
/* JMP 0 A -- JUMP TO A */
/* JPC 0 A -- JUMP CONDITIONAL TO A */
char CH; /*LAST CHAR READ*/
SYMBOL SYM; /*LAST SYMBOL READ*/
ALFA ID; /*LAST IDENTIFIER READ*/
int NUM; /*LAST NUMBER READ*/
int CC; /*CHARACTER COUNT*/
int LL; /*LINE LENGTH*/
int CX; /*CODE ALLOCATION INDEX*/
char LINE[81];
INSTRUCTION CODE[CXMAX];
ALFA KWORD[NORW+1];
SYMBOL WSYM[NORW+1];
SYMBOL SSYM['^'+1];
ALFA MNEMONIC[9];
SYMSET DECLBEGSYS, STATBEGSYS, FACBEGSYS;
struct {
ALFA NAME;
OBJECTS KIND;
union {
int VAL; /*CONSTANT*/
struct { int LEVEL,ADR,SIZE; } vp; /*VARIABLE,PROCEDUR:*/
};
} TABLE[TXMAX];
FILE *FIN,*FOUT;
int ERR;
void EXPRESSION(SYMSET FSYS, int LEV, int &TX);
void TERM(SYMSET FSYS, int LEV, int &TX);
//---------------------------------------------------------------------------
int SymIn(SYMBOL SYM, SYMSET S1) {
return S1[SYM];
}
//---------------------------------------------------------------------------
SYMSET SymSetUnion(SYMSET S1, SYMSET S2) {
SYMSET S=(SYMSET)malloc(sizeof(int)*41);
for (int i=0; i<41; i++)
if (S1[i] || S2[i]) S[i]=1;
else S[i]=0;
return S;
}
//---------------------------------------------------------------------------
SYMSET SymSetAdd(SYMBOL SY, SYMSET S) {
SYMSET S1;
S1=(SYMSET)malloc(sizeof(int)*41);
for (int i=0; i<41; i++) S1[i]=S[i];
S1[SY]=1;
return S1;
}
//---------------------------------------------------------------------------
SYMSET SymSetNew(SYMBOL a) {
SYMSET S; int i,k;
S=(SYMSET)malloc(sizeof(int)*41);
for (i=0; i<41; i++) S[i]=0;
S[a]=1;
return S;
}
//---------------------------------------------------------------------------
SYMSET SymSetNew(SYMBOL a, SYMBOL b) {
SYMSET S; int i,k;
S=(SYMSET)malloc(sizeof(int)*41);
for (i=0; i<41; i++) S[i]=0;
S[a]=1; S[b]=1;
return S;
}
//---------------------------------------------------------------------------
SYMSET SymSetNew(SYMBOL a, SYMBOL b, SYMBOL c) {
SYMSET S; int i,k;
S=(SYMSET)malloc(sizeof(int)*41);
for (i=0; i<41; i++) S[i]=0;
S[a]=1; S[b]=1; S[c]=1;
return S;
}
//---------------------------------------------------------------------------
SYMSET SymSetNew(SYMBOL a, SYMBOL b, SYMBOL c, SYMBOL d) {
SYMSET S; int i,k;
S=(SYMSET)malloc(sizeof(int)*41);
for (i=0; i<41; i++) S[i]=0;
S[a]=1; S[b]=1; S[c]=1; S[d]=1;
return S;
}
//---------------------------------------------------------------------------
SYMSET SymSetNew(SYMBOL a, SYMBOL b, SYMBOL c, SYMBOL d,SYMBOL e) {
SYMSET S; int i,k;
S=(SYMSET)malloc(sizeof(int)*41);
for (i=0; i<41; i++) S[i]=0;
S[a]=1; S[b]=1; S[c]=1; S[d]=1; S[e]=1;
return S;
}
//---------------------------------------------------------------------------
SYMSET SymSetNew(SYMBOL a, SYMBOL b, SYMBOL c, SYMBOL d,SYMBOL e, SYMBOL f) {
SYMSET S; int i,k;
S=(SYMSET)malloc(sizeof(int)*41);
for (i=0; i<41; i++) S[i]=0;
S[a]=1; S[b]=1; S[c]=1; S[d]=1; S[e]=1; S[f]=1;
return S;
}
//---------------------------------------------------------------------------
SYMSET SymSetNULL() {
SYMSET S; int i,n,k;
S=(SYMSET)malloc(sizeof(int)*41);
for (i=0; i<41; i++) S[i]=0;
return S;
}
//---------------------------------------------------------------------------
void Error(int n) {
String s = "***"+AnsiString::StringOfChar(' ', CC-1)+"^";
Form1->printls(s.c_str(),n); fprintf(FOUT,"%s%d\n", s.c_str(), n);
ERR++;
} /*Error*/
//---------------------------------------------------------------------------
void GetCh() {
if (CC==LL) {
if (feof(FIN)) {
Form1->printfs("PROGRAM INCOMPLETE");
fprintf(FOUT,"PROGRAM INCOMPLETE\n");
fclose(FOUT);
exit(0);
}
LL=0; CC=0;
CH=' ';
while (!feof(FIN) && CH!=10)
{ CH=fgetc(FIN); LINE[LL++]=CH; }
LINE[LL-1]=' '; LINE[LL]=0;
String s=IntToStr(CX);
while(s.Length()<3) s=" "+s;
s=s+" "+LINE;
Form1->printfs(s.c_str());
fprintf(FOUT,"%s\n",s);
}
CH=LINE[CC++];
} /*GetCh()*/
//---------------------------------------------------------------------------
void GetSym() {
int i,J,K; ALFA A;
while (CH<=' ') GetCh();
if (CH>='A' && CH<='Z') { /*ID OR RESERVED WORD*/
K=0;
do {
if (K<AL) A[K++]=CH;
GetCh();
}while((CH>='A' && CH<='Z')||(CH>='0' && CH<='9'));
A[K]='\0';
strcpy(ID,A); i=1; J=NORW;
do {
K=(i+J) / 2;
if (strcmp(ID,KWORD[K])<=0) J=K-1;
if (strcmp(ID,KWORD[K])>=0) i=K+1;
}while(i<=J);
if (i-1 > J) SYM=WSYM[K];
else SYM=IDENT;
}
else
if (CH>='0' && CH<='9') { /*NUMBER*/
K=0; NUM=0; SYM=NUMBER;
do {
NUM=10*NUM+(CH-'0');
K++; GetCh();
}while(CH>='0' && CH<='9');
if (K>NMAX) Error(30);
}
else
if (CH==':') {
GetCh();
if (CH=='=') { SYM=BECOMES; GetCh(); }
else SYM=NUL;
}
else /* THE FOLLOWING TWO CHECK WERE ADDED
BECAUSE ASCII DOES NOT HAVE A SINGLE CHARACTER FOR <= OR >= */
if (CH=='<') {
GetCh();
if (CH=='=') { SYM=LEQ; GetCh(); }
else if (CH=='>') { SYM=NEQ; GetCh(); }
else SYM=LSS;
}
else
if (CH=='>') {
GetCh();
if (CH=='=') { SYM=GEQ; GetCh(); }
else SYM=GTR;
}
else
if (CH=='+') {
GetCh();
if (CH=='=') { SYM=PEQ; GetCh(); }
else if (CH=='+') {SYM=INC;GetCh();}
else
SYM=PLUS;
}
else
if (CH=='-') {
GetCh();
if (CH=='=') { SYM=MEQ; GetCh(); }
else if (CH=='-') {SYM=DEC;GetCh();}
else
SYM=MINUS;
}
else
if (CH=='<')
{
GetCh();
if (CH=='=') { SYM=LEQ; GetCh(); }
else
if(CH=='>') { SYM=NEQ; GetCh();}
else SYM=LSS;
}
else { SYM=SSYM[CH]; GetCh(); }
} /*GetSym()*/
//---------------------------------------------------------------------------
void GEN(FCT X, int Y, int Z) {
if (CX>CXMAX) {
Form1->printfs("PROGRAM TOO LONG");
fprintf(FOUT,"PROGRAM TOO LONG\n");
fclose(FOUT);
exit(0);
}
CODE[CX].F=X; CODE[CX].L=Y; CODE[CX].A=Z;
CX++;
} /*GEN*/
//---------------------------------------------------------------------------
void TEST(SYMSET S1, SYMSET S2, int N) {
if (!SymIn(SYM,S1)) {
Error(N);
while (!SymIn(SYM,SymSetUnion(S1,S2))) GetSym();
}
} /*TEST*/
//---------------------------------------------------------------------------
void ENTER(OBJECTS K, int LEV, int &TX, int &DX) { /*ENTER OBJECT INTO TABLE*/
TX++;
strcpy(TABLE[TX].NAME,ID); TABLE[TX].KIND=K;
switch (K) {
case CONSTANT:
if (NUM>AMAX) { Error(31); NUM=0; }
TABLE[TX].VAL=NUM;
break;
case VARIABLE:
TABLE[TX].vp.LEVEL=LEV; TABLE[TX].vp.ADR=DX; DX++;
break;
case PROCEDUR:
TABLE[TX].vp.LEVEL=LEV;
break;
}
} /*ENTER*/
//---------------------------------------------------------------------------
int POSITION(ALFA ID, int TX) { /*FIND IDENTIFIER IN TABLE*/
int i=TX;
strcpy(TABLE[0].NAME,ID);
while (strcmp(TABLE[i].NAME,ID)!=0) i--;
return i;
} /*POSITION*/
//---------------------------------------------------------------------------
void ConstDeclaration(int LEV,int &TX,int &DX) {
if (SYM==IDENT) {
GetSym();
if (SYM==EQL||SYM==BECOMES) {
if (SYM==BECOMES) Error(1);
GetSym();
if (SYM==NUMBER) { ENTER(CONSTANT,LEV,TX,DX); GetSym(); }
else Error(2);
}
else Error(3);
}
else Error(4);
} /*ConstDeclaration()*/
//---------------------------------------------------------------------------
void VarDeclaration(int LEV,int &TX,int &DX) {
if (SYM==IDENT) { ENTER(VARIABLE,LEV,TX,DX); GetSym(); }
else Error(4);
} /*VarDeclaration()*/
//---------------------------------------------------------------------------
void ListCode(int CX0) { /*LIST CODE GENERATED FOR THIS Block*/
if (Form1->ListSwitch->ItemIndex==0)
for (int i=CX0; i<CX; i++) {
String s=IntToStr(i);
while(s.Length()<3)s=" "+s;
s=s+" "+MNEMONIC[CODE[i].F]+" "+IntToStr(CODE[i].L)+" "+IntToStr(CODE[i].A);
Form1->printfs(s.c_str());
fprintf(FOUT,"%3d%5s%4d%4d\n",i,MNEMONIC[CODE[i].F],CODE[i].L,CODE[i].A);
}
} /*ListCode()*/;
//---------------------------------------------------------------------------
void FACTOR(SYMSET FSYS, int LEV, int &TX) {
int i;
TEST(FACBEGSYS,FSYS,24);
while (SymIn(SYM,FACBEGSYS)) {
if (SYM==IDENT) {
i=POSITION(ID,TX);
if (i==0) Error(11);
else
switch (TABLE[i].KIND) {
case CONSTANT: GEN(LIT,0,TABLE[i].VAL); break;
case VARIABLE: GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR); break;
case PROCEDUR: Error(21); break;
}
GetSym();
}
else
if (SYM==NUMBER) {
if (NUM>AMAX) { Error(31); NUM=0; }
GEN(LIT,0,NUM); GetSym();
}
else
if (SYM==LPAREN) {
GetSym(); EXPRESSION(SymSetAdd(RPAREN,FSYS),LEV,TX);
if (SYM==RPAREN) GetSym();
else Error(22);
}
TEST(FSYS,FACBEGSYS,23);
}
}/*FACTOR*/
//---------------------------------------------------------------------------
void TERM(SYMSET FSYS, int LEV, int &TX) { /*TERM*/
SYMBOL MULOP;
FACTOR(SymSetUnion(FSYS,SymSetNew(TIMES,SLASH)), LEV,TX);
while (SYM==TIMES || SYM==SLASH) {
MULOP=SYM; GetSym();
FACTOR(SymSetUnion(FSYS,SymSetNew(TIMES,SLASH)),LEV,TX);
if (MULOP==TIMES) GEN(OPR,0,4);
else GEN(OPR,0,5);
}
} /*TERM*/;
//---------------------------------------------------------------------------
void EXPRESSION(SYMSET FSYS, int LEV, int &TX) {
SYMBOL ADDOP;
if (SYM==PLUS || SYM==MINUS) {
ADDOP=SYM; GetSym();
TERM(SymSetUnion(FSYS,SymSetNew(PLUS,MINUS)),LEV,TX);
if (ADDOP==MINUS) GEN(OPR,0,1);
}
/* else if (SYM==NUMBER) {//ADDOP=SYM; GetSym();
//TERM(FSYS,LEV,TX);
GEN(OPR,0,2);} */
else TERM(SymSetUnion(FSYS,SymSetNew(PLUS,MINUS)),LEV,TX);
while (SYM==PLUS || SYM==MINUS) {
ADDOP=SYM; GetSym();
TERM(SymSetUnion(FSYS,SymSetNew(PLUS,MINUS)),LEV,TX);
if (ADDOP==PLUS) GEN(OPR,0,2);
else GEN(OPR,0,3);
}
} /*EXPRESSION*/
//---------------------------------------------------------------------------
void CONDITION(SYMSET FSYS,int LEV,int &TX) {
SYMBOL RELOP;
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,j,CX1,CX2;
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==PEQ) {GetSym();
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
EXPRESSION(FSYS,LEV,TX);
GEN(OPR,0,2); }
else if (SYM==MEQ){ GetSym();
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
EXPRESSION(FSYS,LEV,TX);
GEN(OPR,0,3); }
else if(SYM==INC){ GetSym();
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
GEN(LIT,0,1);
GEN(OPR,0,2);
}
else if(SYM==DEC){ GetSym();
GEN(LOD,LEV-TABLE[i].vp.LEVEL,TABLE[i].vp.ADR);
GEN(LIT,0,1);
GEN(OPR,0,3);
}
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,ELSESYM),FSYS),LEV,TX);
if (SYM==THENSYM) GetSym();
else Error(16);
CX1=CX;
GEN(JPC,0,0);
// break;
STATEMENT(SymSetUnion(SymSetNew(ELSESYM),FSYS),LEV,TX);
GetSym();
if(SYM==ELSESYM){CX2=CX; GEN(JMP,0,0);
GetSym();CODE[CX1].A=CX;
STATEMENT(FSYS,LEV,TX);
CODE[CX2].A=CX;}
else CODE[CX1].A=CX;
break;
case FORSYM:
GetSym();
j=POSITION(ID,TX);
STATEMENT(SymSetUnion(SymSetNew(TOSYM,DOWNTOSYM),FSYS),LEV,TX);
if(SYM==TOSYM){//步长为 1 的情况；
CX1=CX;
GetSym();
EXPRESSION(SymSetAdd(DOSYM,FSYS),LEV,TX);
GEN(LOD,LEV-TABLE[j].vp.LEVEL,TABLE[j].vp.ADR);
GEN(OPR,0,11);
CX2=CX;
GEN(JPC,0,0);
if(SYM==DOSYM){
GetSym();
STATEMENT(FSYS,LEV,TX);
}
GEN(LIT,0,1);
GEN(LOD,LEV-TABLE[j].vp.LEVEL,TABLE[j].vp.ADR);
GEN(OPR,0,2);
GEN(STO,LEV-TABLE[j].vp.LEVEL,TABLE[j].vp.ADR);
GEN(JMP,0,CX1);
CODE[CX2].A=CX;
}
else if(SYM==DOWNTOSYM){//步长为 -1 的情况；
CX1=CX;
GetSym();
EXPRESSION(SymSetAdd(DOSYM,FSYS),LEV,TX);
GEN(LOD,LEV-TABLE[j].vp.LEVEL,TABLE[j].vp.ADR);
GEN(OPR,0,13);
CX2=CX;
GEN(JPC,0,0);
if(SYM==DOSYM){
GetSym();
STATEMENT(FSYS,LEV,TX);
}
GEN(LOD,LEV-TABLE[j].vp.LEVEL,TABLE[j].vp.ADR);
GEN(LIT,0,1);
GEN(OPR,0,3);
GEN(STO,LEV-TABLE[j].vp.LEVEL,TABLE[j].vp.ADR);
GEN(JMP,0,CX1);
CODE[CX2].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;
}
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;
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