View source for Foreach statement (TADS 3)

The foreach statement in TADS 3 allows you to easily loop over a collection, much like a <b>for</b> loop but it saves the author from defining index variables just to refer to each element in the collection. 

==[[Syntax (style guide)|Syntax]]==
In TADS 3 only:
 <b>foreach (</b><i>var</i> <b>in</b> <i>expression</i><b>) {</b> <i>body</i> <b>}</b>

==Example==

Suppose we want to print a list of numbers, one per line.

<pre>local lst = [2, 3, 5, 7, 11];

foreach ( local x in lst ) {
    "<<x>>\n";
}</pre>

==Another example==

This time, we want to add the names of every object in a room <i>StartRoom</i> to a list <i>lst</i>. Here's a way to do it using <b>foreach</b>.

<pre>local lst = [];

foreach ( local obj in StartRoom.contents ) {
    lst += obj.name;
}</pre>

==Coding note==

Note that because of the way the iteration is done, if you change the collection you are iterating over whilst the iteration is underway, the elements you iterate over are <b>not</b> affected. For example,

<pre>local lst = [1];

foreach ( local x in lst) {
    lst.append(x);
}</pre>

does <b>not</b> send the program into an infinite loop (which you would expect if <b>foreach</b> updated <i>lst</i> after each iteration). At the end of this code, <i>lst</i> is [1, 1]. See the TADS 3 documentation for more information.

[[Category:Statements_(TADS)]]