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法律研究檢測 C 程式中令牌的 C 程式
此處，我們將建立一個 c 程式來檢測 C 程式中的令牌。這稱為編譯器的詞法分析階段。詞法分析器是檢測程式令牌並將其傳送至語法分析器的編譯器部分。
令牌是程式碼的最小實體，它要麼是關鍵字、識別符號、常數、字串文字或符號。
C 中不同型別令牌的示例。
示例
Keywords: for, if, include, etc Identifier: variables, functions, etc separators: ‘,’, ‘;’, etc operators: ‘-’, ‘=’, ‘++’, etc
檢測 C 程式中令牌的程式−
示例
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
bool isValidDelimiter(char ch) {
if (ch == ' ' || ch == '+' || ch == '-' || ch == '*' ||
ch == '/' || ch == ',' || ch == ';' || ch == '>' ||
ch == '<' || ch == '=' || ch == '(' || ch == ')' ||
ch == '[' || ch == ']' || ch == '{' || ch == '}')
return (true);
return (false);
}
bool isValidOperator(char ch){
if (ch == '+' || ch == '-' || ch == '*' ||
ch == '/' || ch == '>' || ch == '<' ||
ch == '=')
return (true);
return (false);
}
// Returns 'true' if the string is a VALID IDENTIFIER.
bool isvalidIdentifier(char* str){
if (str[0] == '0' || str[0] == '1' || str[0] == '2' ||
str[0] == '3' || str[0] == '4' || str[0] == '5' ||
str[0] == '6' || str[0] == '7' || str[0] == '8' ||
str[0] == '9' || isValidDelimiter(str[0]) == true)
return (false);
return (true);
}
bool isValidKeyword(char* str) {
if (!strcmp(str, "if") || !strcmp(str, "else") || !strcmp(str, "while") || !strcmp(str, "do") || !strcmp(str, "break") || !strcmp(str, "continue") || !strcmp(str, "int")
|| !strcmp(str, "double") || !strcmp(str, "float") || !strcmp(str, "return") || !strcmp(str, "char") || !strcmp(str, "case") || !strcmp(str, "char")
|| !strcmp(str, "sizeof") || !strcmp(str, "long") || !strcmp(str, "short") || !strcmp(str, "typedef") || !strcmp(str, "switch") || !strcmp(str, "unsigned")
|| !strcmp(str, "void") || !strcmp(str, "static") || !strcmp(str, "struct") || !strcmp(str, "goto"))
return (true);
return (false);
}
bool isValidInteger(char* str) {
int i, len = strlen(str);
if (len == 0)
return (false);
for (i = 0; i < len; i++) {
if (str[i] != '0' && str[i] != '1' && str[i] != '2'&& str[i] != '3' && str[i] != '4' && str[i] != '5'
&& str[i] != '6' && str[i] != '7' && str[i] != '8' && str[i] != '9' || (str[i] == '-' && i > 0))
return (false);
}
return (true);
}
bool isRealNumber(char* str) {
int i, len = strlen(str);
bool hasDecimal = false;
if (len == 0)
return (false);
for (i = 0; i < len; i++) {
if (str[i] != '0' && str[i] != '1' && str[i] != '2' && str[i] != '3' && str[i] != '4' && str[i] != '5' && str[i] != '6' && str[i] != '7' && str[i] != '8'
&& str[i] != '9' && str[i] != '.' || (str[i] == '-' && i > 0))
return (false);
if (str[i] == '.')
hasDecimal = true;
}
return (hasDecimal);
}
char* subString(char* str, int left, int right) {
int i;
char* subStr = (char*)malloc( sizeof(char) * (right - left + 2));
for (i = left; i <= right; i++)
subStr[i - left] = str[i];
subStr[right - left + 1] = '\0';
return (subStr);
}
void detectTokens(char* str) {
int left = 0, right = 0;
int length = strlen(str);
while (right <= length && left <= right) {
if (isValidDelimiter(str[right]) == false)
right++;
if (isValidDelimiter(str[right]) == true && left == right) {
if (isValidOperator(str[right]) == true)
printf("Valid operator : '%c'
", str[right]);
right++;
left = right;
} else if (isValidDelimiter(str[right]) == true && left != right || (right == length && left != right)) {
char* subStr = subString(str, left, right - 1);
if (isValidKeyword(subStr) == true)
printf("Valid keyword : '%s'
", subStr);
else if (isValidInteger(subStr) == true)
printf("Valid Integer : '%s'
", subStr);
else if (isRealNumber(subStr) == true)
printf("Real Number : '%s'
", subStr);
else if (isvalidIdentifier(subStr) == true
&& isValidDelimiter(str[right - 1]) == false)
printf("Valid Identifier : '%s'
", subStr);
else if (isvalidIdentifier(subStr) == false
&& isValidDelimiter(str[right - 1]) == false)
printf("Invalid Identifier : '%s'
", subStr);
left = right;
}
}
return;
}
int main(){
char str[100] = "float x = a + 1b; ";
printf("The Program is : '%s'
", str);
printf("All Tokens are :
");
detectTokens(str);
return (0);
}輸出
The Program is : 'float x = a + 1b; ' All Tokens are : Valid keyword : 'float' Valid Identifier : 'x' Valid operator : '=' Valid Identifier : 'a' Valid operator : '+' Invalid Identifier : '1b'
更新於：07-Oct-2023
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