GNU Smalltalk: Difference between revisions

{{implementation|Smalltalk}}'''GNU Smalltalk''' is an implementation of the [[:Category:Smalltalk|Smalltalk]] programming language by the GNU Project. For download, see [http://smalltalk.gnu.org/ http://smalltalk.gnu.org/].

These examples only work on GNU Smalltalk 3.0 and later versions. Classic [[Hello world]] example:

<pre>"Everything, including a literal, is an object, so this works:"

-199 abs "199"

'gst is cool' size "11"

'Slick' indexOf: $c "4"

'Nice Day Isn''t It?' asLowercase asSet asSortedCollection asString "' '?acdeinsty'"</pre>

A method such as ''inject:into:'' can accept both a parameter and a block. It iterates over each member of a list, performing some function on while retaining an aggregate. This is analogous to the [[foldl]] function in [[Haskell]]. For example:

The following code defines a class named Person. By deriving from Magnitude, it automatically defines all comparison methods except one (<codett>&lt;</codett>). With the addition of that one, <codett>asSortedCollection</codett> can sort by age. Note that we can override the way the object is printed/displayed (the default is to share the programmer-print and user-display representation) by overriding <codett>printOn:</codett>.

An exception is raised with a <codett>halt</codett> call:

An optional message can be added to the exception; there's also <codett>error:</codett> which raises a different kind of exception:

These are actually wrappers for the actual exception raising method, <codett>signal</tt>: