114 lines
2.4 KiB
C
114 lines
2.4 KiB
C
#include <ctype.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
|
|
typedef enum { TOKEN_INT, TOKEN_PLUS, TOKEN_MUL, TOKEN_DIV, TOKEN_LPAREN, TOKEN_RPAREN, TOKEN_EOF } TokenType;
|
|
|
|
typedef struct {
|
|
TokenType type;
|
|
int value;
|
|
} Token;
|
|
|
|
const char *input;
|
|
size_t pos;
|
|
Token current_token;
|
|
|
|
void skip_whitespace() {
|
|
while (isspace(input[pos])) pos++;
|
|
}
|
|
|
|
Token get_next_token() {
|
|
skip_whitespace();
|
|
|
|
char ch = input[pos];
|
|
|
|
if (ch == '\0')
|
|
return (Token){TOKEN_EOF, 0};
|
|
|
|
if (isdigit(ch)) {
|
|
int val = 0;
|
|
while (isdigit(input[pos])) {
|
|
val = val * 10 + (input[pos++] - '0');
|
|
}
|
|
return (Token){TOKEN_INT, val};
|
|
}
|
|
|
|
pos++;
|
|
switch (ch) {
|
|
case '+': return (Token){TOKEN_PLUS, 0};
|
|
case '*': return (Token){TOKEN_MUL, 0};
|
|
case '/': return (Token){TOKEN_DIV, 0};
|
|
case '(': return (Token){TOKEN_LPAREN, 0};
|
|
case ')': return (Token){TOKEN_RPAREN, 0};
|
|
default: fprintf(stderr, "Unexpected character: %c\n", ch); exit(1);
|
|
}
|
|
}
|
|
|
|
void eat(TokenType type) {
|
|
if (current_token.type == type) {
|
|
current_token = get_next_token();
|
|
} else {
|
|
fprintf(stderr, "Unexpected token\n");
|
|
exit(1);
|
|
}
|
|
}
|
|
|
|
int expr();
|
|
|
|
int factor() {
|
|
Token tok = current_token;
|
|
|
|
if (tok.type == TOKEN_INT) {
|
|
eat(TOKEN_INT);
|
|
return tok.value;
|
|
} else if (tok.type == TOKEN_LPAREN) {
|
|
eat(TOKEN_LPAREN);
|
|
int result = expr();
|
|
eat(TOKEN_RPAREN);
|
|
return result;
|
|
} else {
|
|
fprintf(stderr, "Expected integer or '('\n");
|
|
exit(1);
|
|
}
|
|
}
|
|
|
|
int term() {
|
|
int result = factor();
|
|
while (current_token.type == TOKEN_MUL) {
|
|
eat(TOKEN_MUL);
|
|
result *= factor();
|
|
}
|
|
while (current_token.type == TOKEN_DIV) {
|
|
eat(TOKEN_DIV);
|
|
result /= factor();
|
|
}
|
|
return result;
|
|
}
|
|
|
|
int expr() {
|
|
int result = term();
|
|
while (current_token.type == TOKEN_PLUS) {
|
|
eat(TOKEN_PLUS);
|
|
result += term();
|
|
}
|
|
return result;
|
|
}
|
|
|
|
int main() {
|
|
char buffer[256];
|
|
printf("Enter expression: ");
|
|
fgets(buffer, sizeof(buffer), stdin);
|
|
|
|
input = buffer;
|
|
pos = 0;
|
|
current_token = get_next_token();
|
|
|
|
int result = expr();
|
|
if (current_token.type != TOKEN_EOF) {
|
|
fprintf(stderr, "Unexpected extra input\n");
|
|
return 1;
|
|
}
|
|
|
|
printf("Result = %d\n", result);
|
|
return 0;
|
|
}
|