将简单循环转换为do-while

我如何将以下while循环转换为正确的循环do-while而不第一次重复计算？

void ctype()
{
    char c;
    while ((c = getchar()) != '.')
        printf("'%c' is %s a letter.n", c, isalpha(c)? "indeed" : "not");
    printf("'%c' is %s a letter.n", c, isalpha(c)? "indeed" : "not");
}

到目前为止我所拥有的是：

void ctype()
// Print the letters up through the period, but quit on the period
{
    char c = getchar();
    do {
        printf("'%c' is %s a letter.n", c, isalpha(c)? "indeed" : "not");
    } while ((c = getchar()) != '.') 
}

但是这个 double-getchar在第一项上。这样做的正确方法是什么？这几乎就像我想要getchar()在 while 循环中的后增量等效。

while循环的示例输入/输出，目前是正确的：

$ run
.
'.' is not a letter.
$ run
Hello.
'H' is indeed a letter.
'e' is indeed a letter.
'l' is indeed a letter.
'l' is indeed a letter.
'o' is indeed a letter.
'.' is not a letter.

回答

char c;
do {
    c = getchar();
    printf("'%c' is %s a letter.n", c, isalpha(c)? "indeed" : "not");
} while(c != '.');

while(<expr>) {
    // Body
}

do {
    if(<expr>) break;

    // Body
} while(1);

int c;
do {
    c = getchar();
    if(c == EOF) break;
    printf("'%c' is %s a letter.n", c, isalpha(c)? "indeed" : "not");
} while(c != '.');

回答

    int c;
    while ((c = getchar()) != EOF)
    {
        printf("'%c' is %s a letter.n", c, isalpha(c)? "indeed" : "not");
        if(c == '.') break;
    }