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History variables: Difference between revisions
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→{{header|Elena}}
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imported>Arakov |
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Sum of the historic values: 6
</pre>
=={{header|Arturo}}==
<syntaxhighlight lang="arturo">define :history [][
init: [
this\record: @[0]
]
]
assign: function [historyVar,newValue][
historyVar\record: historyVar\record ++ newValue
]
alias.infix {'-->} 'assign
records: function [historyVar][
historyVar\record
]
retrieve: function [historyVar][
result: last historyVar\record
historyVar\record: chop historyVar\record
return result
]
current: function [historyVar][
return last historyVar\record
]
do [
h: to :history []
print "Assigning three values: 1, 2, 3..."
h --> 1
h --> 2
h --> 3
print "\nHistory (oldest values first):"
print [">" records h]
print ["\nCurrent value is:" current h]
print "\nRecalling the three values..."
loop 1..3 'x ->
print ["- Recalled:" retrieve h]
print "\nHistory:"
print [">" records h]
]</syntaxhighlight>
{{out}}
<pre>Assigning three values: 1, 2, 3...
History (oldest values first):
> [0 1 2 3]
Current value is: 3
Recalling the three values...
- Recalled: 3
- Recalled: 2
- Recalled: 1
History:
> [0] </pre>
=={{header|AspectJ}}==
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{{out}}
<pre>foobar <- foo <- 5
</pre>
=={{header|C++}}==
C++ does not have history variables, but they can easily by implemented with a generic class.
<syntaxhighlight lang="c++">
#include <deque>
#include <iostream>
#include <string>
template <typename T>
class with_history {
public:
with_history(const T& element) {
history.push_front(element);
}
T get() {
return history.front();
}
void set(const T& element) {
history.push_front(element);
}
std::deque<T> get_history() {
return std::deque<T>(history);
}
T rollback() {
if ( history.size() > 1 ) {
history.pop_front();
}
return history.front();
}
private:
std::deque<T> history;
};
int main() {
with_history<double> number(1.2345);
std::cout << "Current value of number: " << number.get() << std::endl;
number.set(3.4567);
number.set(5.6789);
std::cout << "Historical values of number: ";
for ( const double& value : number.get_history() ) {
std::cout << value << " ";
}
std::cout << std::endl << std::endl;
with_history<std::string> word("Goodbye");
word.set("Farewell");
word.set("Hello");
std::cout << word.get() << std::endl;
word.rollback();
std::cout << word.get() << std::endl;
word.rollback();
std::cout << word.get() << std::endl;
word.rollback();
std::cout << word.get() << std::endl;
word.rollback();
}
</syntaxhighlight>
{{ out }}
<pre>
Current value of number: 1.2345
Historical values of number: 5.6789 3.4567 1.2345
Hello
Farewell
Goodbye
Goodbye
</pre>
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=={{header|Elena}}==
ELENA
<syntaxhighlight lang="elena">import extensions;
import system'collections;
Line 805 ⟶ 944:
console.printLine(o);
o.forEach
o.undo().undo().undo();
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hist: seq[T]
## Initialize a history variable with given value.
result.hist.add value
Line 2,875 ⟶ 3,014:
{{trans|Kotlin}}
Not built in but we can soon make a suitable class.
<syntaxhighlight lang="
construct new(initValue) {
_history = [initValue]
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