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Ch8函数探幽/默认参数/left.cpp

+//left.cpp -- string function with a default argument
+#include <iostream>
+const int Arsize = 80;
+char* left(const char* str, int n = 1);
+
+int main(void)
+{
+	using namespace std;
+	char sample[Arsize];
+
+	cout << "Enter a string:\n";
+	cin.get(sample, Arsize);
+	char* ps = left(sample, 4);
+
+	cout << ps << endl;
+	delete[]ps;				//free old string
+	ps = left(sample);
+	cout << ps << endl;
+	delete[]ps;				//free new string
+
+
+
+	return 0;
+}
+
+char* left(const char* str, int n)
+{
+	if (n < 0)
+	{
+		n = 0;
+	}
+	char* p = new char[n + 1];
+	int i;
+	for ( i = 0; i < n && str[i]; i++)
+	{
+		p[i] = str[i];			//copy characters
+	}
+
+	while (i <= n)
+	{
+		p[i++] = '\0';			//set rest of string to'\0'
+	}
+	return p;
+}