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History variables: Difference between revisions
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123
a b c d
</pre>
=={{header|zkl}}==
No native support, here is a something that can be done with a class:
<lang zkl>class HistoryVar{
var [private] _v, _history=List(), maxSz;
fcn init(v,maxEntries=3){ maxSz=maxEntries; set(v) }
fcn set(v){
_v=v; _history.append(T(Time.Clock.time,v));
if(_history.len()>maxSz) _history.del(0);
self
}
fcn get(n=0){ // look back into history
z:=_history.len();
n=(if(n>=z) 0 else z-n-1);
_history[n][1]
}
var [proxy] v=fcn{ _v };
var [proxy] history=
fcn{ _history.pump(List,fcn([(t,v)]){ T(Time.Date.ctime(t),v) }) };
fcn __opAdd(x){ set(_v + x); self }
}</lang>
<lang zkl>hv:=HistoryVar(123);
hv+4;
hv.set("Shuttle prepared for liftoff");
hv+": orbit achived";
hv.history.concat("\n").println();
hv.get(3).println("<-- value two changes ago");</lang>
{{out}}
<pre>
L("Thu Oct 13 13:48:37 2016",127)
L("Thu Oct 13 13:48:37 2016","Shuttle prepared for liftoff")
L("Thu Oct 13 13:48:37 2016","Shuttle prepared for liftoff: orbit achived")
127<-- value two changes ago
</pre>
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