我一直收到以下错误：
clang -ggdb3 -O0 -std=c99 -Wall -Werror vigenere.c -lcs50 -lm -o vigenere
vigenere.c:29:14: error: unused variable 'key' [-Werror,-Wunused-variable]
string key = GetString();
^
1 error generated.
我的代码如下。我很困惑为什么我会收到错误。如果我采用变量＆＃34; key＆＃34;在do while循环之外它运行正常。只在输入do while循环时才会出错。
#include <stdio.h>
#include <cs50.h>
#include <math.h>
#include <string.h>
//Note 97 thru 122 are lowercase letters and 65 thru 90 are uppercase letters
//They are separated by exactly 32. A is 65 and a is 97
int checkIfAlphaAndCase(char argument); //This is a prototype
int changeLetterToNumber(char argument, int upperOrLower); //This is a prototype
int main(int argc, string argv[]){
printf("\n");
if(argc < 2){ //If the user fails to enter something
//printf("%d\n", argc);
printf("You failed!!!! You must enter an argument to be encrypted after the program name \n");
return 1;
}else{
do{
printf("Please enter a key at least 7 letters long: "); //Let's start by getting a key from the user
string key = GetString();
} while(strlen(key) < 7);
//printf("this is the first char: %c", key[0]);
int keysLength = strlen(key);
int keyChangedToNumbersArray[keysLength];
int alphaAndCaseInt;
int letterToNumber;
for(int i = 0; i < keysLength; i++){ //By using <= I'll add a null character at the end of the array to know when it ends.
//This null character will turn into zero after going through the funtion
//changeLetterToNumber and storing the return value in letterToNumber
alphaAndCaseInt = checkIfAlphaAndCase(key[i]);
//printf("%i", alphaAndCaseInt); //return types are 1 is lower, 2 is upper, and 0 is not a letter
letterToNumber = changeLetterToNumber(key[i], alphaAndCaseInt);
//printf("This is the char turned into a number: %i", letterToNumber);
keyChangedToNumbersArray[i] = letterToNumber;
//printf("This is the letter to Number: %i \n", letterToNumber);
//printf("\n\n");
//printf("%i\n", keyChangedToNumbersArray[i]);
}//This loop changes each letter of the key into a number
printf("\n\n");
//printf("Your encrypted data is: ");
//printf("%i\n", argc);
//printf("%c\n", argv[1][0]);
for(int i = 1; i < argc; i++){ //If a user enters [program] then a name or a string we want to skip over the program name
//and go straight to the string(s) to encrypt them. argc counts the program name in
//its count so we start at 1 to ensure we don't encrypt the program name also. This loop will
//run depending on how many words or characters with spaces there are as each one adds 1 to
//the argc count
//i will start out as 1
printf("%i\n", strlen(argv[i]));
//printf("%i\n", i);
for(int n = 0; n < strlen(argv[i]); n++){
//printf("%c", argv[i][n]);
int argLetterInt = checkIfAlphaAndCase(argv[i][n]);//return types are 1 is lower, 2 is upper, and 0 is not a letter
//printf("%i", argLetterInt);
if(argLetterInt == 1){ //return types are 1 is lower, 2 is upper, and 0 is not a letter
//This if statement is checking to see if the first letter of the argument is a lowercase letter and a letter.
if(keyChangedToNumbersArray[n] > 0 && argv[i][n] + keyChangedToNumbersArray[n] > 122){
printf("%c\n", argv[i][n]);
}else if(keyChangedToNumbersArray[n] > 0 && argv[i][n] + keyChangedToNumbersArray[n] < 122){
printf("%c\n", keyChangedToNumbersArray[n] + argv[i][n]);
}
}
if(argLetterInt == 2){ //return types are 1 is lower, 2 is upper, and 0 is not a letter
//This if statement is checking to see if the first letter of the argument is a lowercase letter and a letter.
if(keyChangedToNumbersArray[n] > 0 && argv[i][n] + keyChangedToNumbersArray[n] > 90){
printf("%c\n", argv[i][n]);
}else if(keyChangedToNumbersArray[n] > 0 && argv[i][n] + keyChangedToNumbersArray[n] < 90){
printf("%c\n", keyChangedToNumbersArray[n] + argv[i][n]);
}
}
}//end for loop
//printf(" ");
//printf("%s ", argv[i]);
printf("\n");
return 0;
}//End Main Function
}
}
int checkIfAlphaAndCase(char argument){
if(argument >= 97 && argument <= 122){
return 1; //must be lowercase
}else if(argument >= 65 && argument <= 97){
return 2; //must be uppcase
}else{
return 0; //must not be a letter
}
}
int changeLetterToNumber(char argument, int upperOrLower){ //Change the char to a number a and A both = 0
int returnValue = 0;
if(upperOrLower == 1){
int lowerCaseLetters[26] = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
for(int i = 0; i < 26; i++){
if(argument == lowerCaseLetters[i]){
returnValue = i;
break;
}
}
}else if(upperOrLower == 2){
int upperCaseLetters[26] = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
for(int i = 0; i < 26; i++){
if(argument == upperCaseLetters[i]){
returnValue = i;
break;
}
}
}
return returnValue;
}
答案 0 :(得分：2)
那些Whacky编译器作者和他们疯狂无意义的错误......
喔。坚持下去，也许它们很有用：
do {
printf("Please enter a key at least 7 letters long: "); //Let's start by getting a key from the user
string key = GetString();
} while(strlen(key) < 7);
key的范围仅限于它所声明的{ }对内（即do-while循环），并且从未在其他任何地方使用过。你知道什么 - 就像编译器说error: unused variable 'key'
试试这个：
string key;
do {
printf("Please enter a key at least 7 letters long: "); //Let's start by getting a key from the user
key = GetString();
} while(strlen(key) < 7);
现在string不仅仅是do while的本地，可以在其他地方使用。 （注意：仍然没有100％清楚字符串是什么......）
PS - 是C或C ++ - C没有string类型。如果它是C ++那么你为什么要使用strlen()？