[Newbies] [Q] How should one concatenate Strings?

Damien Cassou damien.cassou at laposte.net
Tue May 9 18:59:50 UTC 2006

> If you are building very long strings by using , in an inner loop, it
> can be slow because you will have an N squared algorithm.  You can
> convert that into a linear time algorithm by writing to an WriteStream
> using nextPut: and nextPutAll: and then asking the WriteStream for its
> contents.  It leads to a little more complicated code, but on some
> programs in can create a dramatic performance improvement.  In
> general, though, use "comma", since it is simpler.

You should avoid optimizing your code before making sure it needs an 
improvement. Nevertheless, here is a simple benchmark for the two 

[| temp |
   temp := String new.
   (1 to: 100000)
        do: [:i | temp := temp, i asString]] timeToRun

Answers  75.202 milliseconds

[| temp |
   temp := WriteStream on: String new.
   (1 to: 100000)
        do: [:i | temp nextPutAll: i asString]] timeToRun

Answers 3.169 milliseconds

To get the string back from the Stream, use #contents:

myWriteStream contents


Damien Cassou

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