Szathmáry László honlapja @ DEIK

Exercise: Write down the numbers from 1 to 15. The result must be a string.

(1) stringbuffer
def main(): # naive way s = "" for i in range(1, 15 + 1): s = s + str(i) # s += str(i) # print(s) # 123456789101112131415 # better way, with stringbuffer sb = [] for i in range(1, 15 + 1): sb.append(str(i)) # result = "".join(sb) print(result) # 123456789101112131415	import std.stdio; import std.conv; void main() { // naive way string s = ""; foreach (i; 1 .. 15 + 1) { s = s ~ i.to!string; // s ~= i.to!string; } writeln(s); // 123456789101112131415 // better way, with stringbuffer char[] sb; foreach (i; 1 .. 15 + 1) { sb ~= i.to!string.dup; } string result = sb.idup; writeln(result); // 123456789101112131415 }

Notes:

Strings are immutable. When you concatenate two strings, the result is a new string object (naive way).
In D, if you need a mutable "string", you can use a char[] for that purpose. It's a list of characters, and a list can grow in size. You can append elements to it.
dup() returns a mutable copy, in this case a char[] .
idup() returns an immuable copy, in this case a string .
If you have a string, you can convert it to char[] with dup().
If you have a char[], you can convert it to a string with idup().

Stringbuffer