C语言 *初学者* C：不兼容的整数到指针转换将“char”传递给“const char *”类型的参数
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*Beginner* C: incompatible integer to pointer conversion passing 'char' to parameter of type 'const char *'
提问by Ting
I'm trying to convert each letter in a string to it's ASCII number. Using
我正在尝试将字符串中的每个字母转换为它的 ASCII 数字。使用
int letter = (atoi(ptext[i]));
gives me this error:
给我这个错误：
error: incompatible integer to pointer conversion
passing 'char' to parameter of type 'const char *'; take the
address with & [-Werror]
int letter = (atoi(ptext[i]));
^~~~~~~~
&
/usr/include/stdlib.h:148:32: note: passing argument to parameter
'__nptr' here
extern int atoi (__const char *__nptr)
Here is some of the rest of my code that may be relevant:
以下是我的其他一些可能相关的代码：
#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
int main(int argc, string argv[])
{
printf("Give a string to cipher:\n");
string ptext = GetString();
int i = 0;
if (isupper(ptext[i]))
{
int letter = (atoi(ptext[i]));
}
}
What am I doing wrong, and how do I fix this so I can convert a string into ASCII values?
我做错了什么，我该如何解决这个问题，以便将字符串转换为 ASCII 值？
Note: cs50.hlets me use "string" instead of "char*" in main.
注意：cs50.h让我在 main 中使用“ string”而不是“ char*”。
采纳答案by Artur
You do not need to convert characters to a number. It is a matter of interpretation of your data.
您不需要将字符转换为数字。这是对您的数据的解释问题。
Charater 'A' can be thought of 0x41 or 65 so this is perfectly fine:
字符 'A' 可以被认为是 0x41 或 65，所以这完全没问题：
int number = 'A';
and value on variable number is 0x41/65 or 1000001b depending how you want to present it/treat it.
变量编号的值是 0x41/65 或 1000001b，具体取决于您希望如何呈现/处理它。
As for interpretation : 0xFF may be treated as 255 if you present it as unsigned value or even as -1 when treated as signed and kept in 8 bits.
至于解释：如果将 0xFF 表示为无符号值，则可能将其视为 255，或者将其视为有符号并保留为 8 位时甚至视为 -1。
So your question:
所以你的问题：
can convert a string into ASCII values?
可以将字符串转换为 ASCII 值吗？
is kind of wrong - all characters of the string are already ascii values - it is just a matter of how you treat/print/interpret/present them.
有点错误 - 字符串的所有字符都已经是 ascii 值 - 这只是你如何对待/打印/解释/呈现它们的问题。
回答by
atoi()expects a string. You only want the char code of the character... which is the character itself,since in C, the charis a normal integer type just like every other integer, and a string is an array of chars which hold the character codes themselves.
atoi()期待一个字符串。您只需要字符的 char 代码......这是字符本身，因为在 C 中， thechar是一个普通的整数类型，就像其他所有整数一样，而字符串是一个chars数组，其中包含字符代码本身。
Consequently,
最后，
int letter = ptext[i];
would do the job.
会做的工作。
回答by Gangadhar
int letter = (atoi(ptext[i]));
atoi()convert string to integer not character.
atoi()将字符串转换为整数而不是字符。
To store ascii value of character into integer variable Do direct assignment of character to integer variable.
将字符的ascii 值存入整型变量 将字符直接赋值给整型变量。
int letter = ptext[i];
