C
const char *s1 = "hello";
const char *s2 = " world";
char *s3 = (char *)malloc(strlen(s1)+strlen(s2)+1);
strcpy(s3, s1);
strcat(s3, s2);
C++
string s1 = "hello";
s1 += " world";
string s1 = "hello";
string s2 = s1 + " world";
CoffeeScript
'hello' + ' world'
JavaScript
'hello' + ' world'
Kotlin
"hello" + " world"
Objective-C
NSMutableString *s1 = [@"hello" mutableCopy];
[s1 appendString:@" world"];
NSString *s1 = @"hello";
NSString *s2 = [s1 stringByAppendingString:@" world"];
Python
'hello' + ' world'