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lex.cpp
212 lines (194 loc) · 5.18 KB
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lex.cpp
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#include <stdio.h>
#include <string.h>
#include <cstdlib>
char program[500];
int p = 0; // for moving program array
char token[16];
int category;
int line = 1; // line num
const char *msg;
const char *keywords[9] = {"begin", "end", "integer", "if", "then", "else", "function", "read", "write"};
bool isDigit(char ch) {
return ch >= '0' && ch <= '9';
}
bool isLetter(char ch) {
return (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z');
}
void lexAnalyze() {
char ch;
int n = 0;
for (n = 0; n < 16; n++) token[n] = '\0';
category = 0;
n = 0;
ch = program[p];
p++;// p is the next
while (ch == ' ') {
ch = program[p++];
}
if (isDigit(ch)) {
// is digit
while (isDigit(ch)) {
token[n++] = ch;
ch = program[p++];
}
category = 11;
p--;
} else if (isLetter(ch)) {
while (isDigit(ch) || isLetter(ch)) {
token[n++] = ch;
ch = program[p++];
}
category = 10; // identify
p--;
// is keywords
for (n = 0; n < 9; n++) {
if (strcmp(token, keywords[n]) == 0) {
category = n + 1;// keywords category id
break;
}
}
} else {
switch (ch) {
case '=':
token[0] = '=';
category = 12;
break;
case '<':
ch = program[p];
if (ch == '=') {
token[0] = '<';
token[1] = '=';
category = 14;
p++;
} else if (ch == '>') {
token[0] = '<';
token[1] = '>';
category = 13;
p++;
} else {
token[0] = '<';
category = 15;
}
break;
case '>':
ch = program[p];
if (ch == '=') {
token[0] = '>';
token[1] = '=';
category = 16;
p++;
} else {
token[0] = '>';
category = 17;
}
break;
case '-':
token[0] = '-';
category = 18;
break;
case '*':
token[0] = '*';
category = 19;
break;
case ':':
ch = program[p];
if (ch == '=') {
token[0] = ':';
token[1] = '=';
category = 20;
p++;
} else {
// handle error
category = -1;
msg = "After \":\" should be \"=\"";
}
break;
case '(':
token[0] = '(';
category = 21;
break;
case ')':
token[0] = ')';
category = 22;
break;
case ';':
token[0] = ';';
category = 23;
break;
case '\n':
line++;
token[0] = 'E';
token[1] = 'O';
token[2] = 'L';
token[3] = 'N';
category = 24;
break;
case '\0':
break;
default:
// handle error
category = -1;
msg = "Invalid character";
break;
}
}
}
int main() {
char temp;
int i = 0;
FILE *sourceFile;
FILE *lexFile;
FILE *errFile;
// read
if ((sourceFile = fopen("source.pas", "r")) == NULL) {
printf("can't open source file");
exit(0);
}
while ((temp = fgetc(sourceFile)) != EOF) {
program[i] = temp;
i++;
}
fclose(sourceFile);
// write
if ((lexFile = fopen("source.dyd", "w")) == NULL) {
printf("can't open lex file");
exit(0);
}
// error
if ((errFile = fopen("lex.err", "w")) == NULL) {
printf("can't open error file");
exit(0);
}
while (p < 500) {
lexAnalyze();
// if file end
if (p == 500) {
token[0] = 'E';
token[1] = 'O';
token[2] = 'F';
category = 25;
}
if (category == -1) {
fputs("***LINE:", errFile);
fprintf(errFile, "%d", line);
fputs(" ", errFile);
fputs(msg, errFile);
fputs("\n", errFile);
}else if (category != 0) {
// print
printf("%s,", token);
printf("%d\n", category);
// write
for (i = 0; i < 16 - strlen(token); i++)
fputc(' ', lexFile);// token align right
fputs(token, lexFile);
fputc(' ', lexFile);
if (category < 10)
fputc(' ', lexFile);// category align right
fprintf(lexFile, "%d", category);
fputc('\n', lexFile);
}
}
fclose(errFile);
fclose(lexFile);
}