History variables: Difference between revisions

=={{header|SenseTalk}}==

SenseTalk does not have native support for history variables, but here is a simple object that can be instantiated to provide a history:

<lang sensetalk>// HistoryVariable.script

properties

history: [], -- a list of all historical values

asTextFormat:"[[the last item of my history]]" -- always display the last value

end properties

to set newValue

push newValue nested into my history

end set

to handle value

return the last item of my history

end value

to rollback

pop my history

return it

end rollback

</lang>

Here is an example how this could be used (note that variables in SenseTalk may hold any type of value):

<lang sensetalk>set x to be a new HistoryVariable

tell x to set "Hello"

put "x is now" && x -- display the current value

tell x to set 88

put "x is now" && x

tell x to set "World"

put "x is now" && x

put "History of x:" && x's history -- non-destructively display the history

tell x to set [9,6,3] -- set it to a list

put "x is now" && x

put "History of x:" && the history of x

put "Rolling back:" && x.rollback -- remove the last value

put "After rollback, x is now" && x

</lang>

{{out}}

<pre>

x is now Hello

x is now 88

x is now World

History of x: ["Hello",88,"World"]

x is now [9,6,3]

History of x: ["Hello",88,"World",[9,6,3]]

Rolling back: [9,6,3]

After rollback, x is now World

</pre>