Anonymous user
History variables: Difference between revisions
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→{{header|Elena}}
(Added Algol W) |
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</lang>
=={{header|Elena}}==
ELENA
<lang elena>import extensions
import system'collections
import system'routines
import extensions'routines
class HistoryVariable
{
object value;
prop object
{
previous.push(this value)
else
{
value := nil
}
}
▲ undo
▲ [
▲ ifnot (_previous isEmpty)
▲ [
▲ _value := _previous pop
▲ ];
▲ [
▲ _value := nilValue
▲ ]
▲ ]
get string Printable() => this value;
▲ enumerator => _previous.
}
public program()
{
var o :=
o
o
o
console
o
o
console
{{out}}
<pre>
Line 653 ⟶ 658:
foo
5
nil
</pre>
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