isdigit到底该怎么用？？

[wwfalcon2008]

如题
请各位帮个忙
谢了

[lj860603]

isdigit判断一个数是否整数。

if (isdigit(a)) //如果a是整型数的话...
{
// ...
}

[wwfalcon2008]

可是………………
#include <iostream>

using namespace std;

#include <cctype>

void jurdge( char x );
void jurdge( int x );

int main()
{
char a = 'a';
int b = 3;

jurdge( a );

cout << endl;
jurdge( b );

cin >> a;
return 0;
}

void jurdge( char x )
{
if ( isdigit( x ) )
{
cout << isdigit( x );
}
else
{
cout << endl << "this is not a digit" << " " << isdigit( x );
}
}

void jurdge( int x )
{
if ( isdigit( x ) )
{
cout << isdigit( x );
}
else
{
cout << endl << "this is not a digit" << " " << isdigit( x );
}
}
的结果是

this is not a digit 0

this is not a digit 0

[lj860603]

isdigit(a) //如果a >= '0' && a <= '9' 条件才成立，这时候isdigit(a)返回一个正数。

[Dugowe]

简单的说
#include <ctype.h>
int isdigit( int ch );


如果参数是0到9之间的数字字符，函数返回非零值，否则返回零值.

char c;
scanf( "%c", &c );
if( isdigit(c) )
printf( "You entered the digit %c\n", c );