Queue/Definition: Difference between revisions
→{{header|Picat}}
Line 4,787:
echo $foo->pop(); //Throws an exception
</lang>
=={{header|Picat}}==
First variant.
<lang Picat>go =>
println("Test 1"),
queue_test1,
nl.
empty(Q) => Q = [].
push(Queue, Value) = Q2 =>
Q2 = [Value] ++ Queue.
pop(Q,_) = _, Q==[] ; var(Q) =>
throw $error(empty_queue,pop,'Q'=Q).
pop(Queue,Q2) = Queue.last() =>
Q2 = [Queue[I] : I in 1..Queue.len-1].
queue_test1 =>
% create an empty queue
println("Start test 2"),
empty(Q0),
printf("Create queue %w%n%n", Q0),
% add numbers 1 and 2
println("Add numbers 1 and 2 : "),
Q1 = Q0.push(1),
Q2 = Q1.push(2),
% display queue
printf("Q2: %w\n\n", Q2),
% pop element
V = Q2.pop(Q3),
% display results
printf("Pop : Value: %w Queue: %w\n\n", V, Q3),
% test the queue
print("Test of the queue: "),
( Q3.empty() -> println("Queue empty"); println("Queue not empty") ),
nl,
% pop the elements
print("Pop the queue : "),
V1 = Q3.pop(Q4),
printf("Value %w Queue : %w%n%n", V1, Q4),
println("Pop empty queue:"),
catch(_V = Q4.pop(_Q5),Exception,println(Exception)),
nl,
println("\nEnd of tests.").</lang>
{{out}}
<pre>Test 1
Create queue []
Add numbers 1 and 2 :
Q2: [2,1]
Pop : Value: 1 Queue: [2]
Test of the queue: Queue not empty
Pop the queue : Value 2 Queue : []
Pop empty queue:
error(empty_queue,pop,Q = [])
End of tests.</pre>
Another approach is to always returns the queue which makes command chaining possible, e,g,
<pre>
Q := Q.push2(1).push2(2),
Q := Q.pop2(V1).pop2(V2)
</pre>
<lang Picat>go2 =>
println("Test 2"),
queue_test2,
nl.
empty2() = [].
push2(Queue, Value) = Q2 =>
Q2 = [Value] ++ Queue.
pop2(Q,_) = _, Q==[] ; var(Q) =>
throw $error(empty_queue,pop,'Q'=Q).
pop2(Queue,V) = [Queue[I] : I in 1..Queue.len-1] =>
V = Queue.last().
queue_test2 =>
% create an empty queue
Q = empty2(),
printf("Create queue %w%n%n", Q),
% add numbers 1 and 2
println("Add numbers 1 and 2 : "),
Q := Q.push2(1).push2(2),
% display queue
printf("Q: %w\n\n", Q),
% pop element
Q := Q.pop2(V),
% display results
printf("Pop : Value: %w Queue: %w\n\n", V, Q),
% test the queue
print("Test of the queue: "),
( Q.empty() -> println("Queue empty"); println("Queue not empty") ),
nl,
% pop the elements
print("Pop the queue : "),
Q := Q.pop2(V2),
printf("Value %w Queue : %w%n%n", V2, Q),
println("Pop empty queue:"),
catch(_ = Q.pop2(_V),Exception,println(Exception)),
% command chaining
println("\nCommand chaining: "),
Q := Q.push2(3).push2(4),
Q := Q.pop2(V3).pop2(V4),
printf("V3: %w V4: %w\n", V3, V4),
nl,
println(q=Q).</lang>
{{out}}
<pre>Test 2
Create queue []
Add numbers 1 and 2 :
Q: [2,1]
Pop : Value: 1 Queue: [2]
Test of the queue: Queue not empty
Pop the queue : Value 2 Queue : []
Pop empty queue:
error(empty_queue,pop,Q = [])
Command chaining:
V3: 3 V4: 4
q = []</pre>
=={{header|PicoLisp}}==
| |||