View source for Iterating over an array - three different for-loops

=== for ===
The traditional C-like for-loop is defined as follows:
<pre>
for (initialization; condition; increment/decrement) {
  statement;
}
</pre>
This is very general, just because nearly everything is possible! The three required expressions may contain any code and may not contain numbers: \\
<pre>
words = ["hello", "hi", "welcome", "me", "you", "they", "meet", "talk", "email"];
for (sentence = ""; urand() < .9; sentence += words[int(urand*length(words))] + " ") {
  print(sentence);
}
</pre>
As you can see, the traditional for-loop is extremely flexible. But for the sake of speed! That is because the three expression are evaluated during each iteration!

=== _for ===
As soon as you like to loop over integer numbers (for instance over the indices of an array) you don't need the above flexibility. Thus, you should use another for-loop, which is defined <u>for this purpose only</u> (see also the [http://www.jedsoft.org/slang/doc/html/slang-8.html#ss8.3 S-Lang manual]):
<pre>
_for variable (start, end, increment/decrement) {
  statement;
}
</pre>
For instance:
<pre>
_for i (0, length(myarray)-1, 1) {
  print(myarray[i]);
}
</pre>

Since S-Lang pre2.3.0-75, it is possible to omit <code>1</code> as the third argument of the <code>_for</code> statement, reducing the above example to 
<pre>
_for i (0, length(myarray)-1) {
  print(myarray[i]);
}
</pre>

=== foreach ===
The last possibility to iterate through an array is to use the foreach-loop (in case you don't need the position of the element within the array). The following example is equivalent to the above one:
<pre>
foreach value (myarray) {
  print(value);
}
</pre>

[[Category:Isis / Slang]]