#include namespace S { /* // non-recursive versions // strlen size_t strlen(char const* a){ size_t sz = 0; while(sz++, *a++); return sz-1; } // strcmp int strcmp(char const* a, char const* b) { while(*a && *b) if(*a < *b) return -1; else if(*a > *b) return 1; else { a++, b++; continue; } return 0; } // strcpy char* strcpy(char* a, char const* b){ char*s=a; while(*b, *a++ = *b++); return *a=0, s; } // strcat char* strcat(char* a, char const*b){ char*o=a; return a+=strlen(a),strcpy(a,b),o; } */ // recursive versions // strlen size_t strlen(char const* a){ return !*a?0:1+strlen(a+1);} // strcmp int strcmp(char const* a,char const* b){ return *a&&*b?*a<*b?-1:*a>*b?1:strcmp(a+1,b+1):0; } // strcpy char* strcpy(char*a, char const*b){ return *b?strcpy((*a=*b,a+1),b+1),a:(*a=0,a);} // strcat char* strcat(char*a,char const*b){ return *a?(strcat(a+1,b),a):strcpy(a,b);} }; int main() { using namespace S; char const* str1 = "abCd"; char const* str2 = "abcd"; char const a[] = "skyhigh"; std::cout<< "String length test: \n\n"; std::cout << "str1 = " << str1 << ", len = " << strlen (str1) << "\n"; std::cout << "a[] = " << a << ", len = " << strlen (a) << "\n"; std::cout << "str = sololearn" << ", len = " << strlen ("sololearn") << "\n"; std::cout << "str = " << ", len = " << strlen ("") << "\n\n"; std::cout << "String compare test: \n\n"; std::cout << "strcmp(\"abCd\",\"abcd\") = " << strcmp(str1, str2) << "\n"; std::cout << "strcmp(\"abcd\",\"abCd\") = " << strcmp(str2, str1) << "\n"; std::cout << "strcmp(\"sololrn\",\"sololrn\") = " << strcmp("sololrn","sololrn") << "\n\n"; std::cout << "String copy test: \n\n"; char ns[50]; std::cout << "strcpy(ns,\"\")\n"; char* returned = strcpy(ns, ""); std::cout << "ns = " << ns << ", len = " << strlen(ns) << "\n"; std::cout << "returned = " << returned << ", len = " << strlen(returned) << "\n\n"; std::cout << "strcpy(ns,\"skyhigh\")\n"; returned = strcpy(ns, a); std::cout << "ns = " << ns << ", len = " << strlen(ns) << "\n"; std::cout << "returned = " << returned << ", len = " << strlen(returned) << "\n\n"; std::cout << "String concatenation test:\n\n"; strcpy(ns, "solo"); std::cout << "ns = " << ns << ", len = " << strlen(ns) << "\n"; returned = strcat(ns, "learn"); std::cout << "strcat(ns, \"learn\") = " << ns << ", len = " << strlen(ns) << "\n"; std::cout << "returned = " << returned << ", len = " << strlen(returned) << "\n\n"; return 0; }

strlen_strcmp_strcpy_strcat.cpp