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linq-queryexecution.dart
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linq-queryexecution.dart
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part of linq_samples;
doQueryExecution() =>
runSamples("LINQ - Query Execution",
{'linq99': 'Deferred Execution',
'linq100': 'Immediate Execution',
'linq101': 'Query Reuse'});
linq99(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var i = 0;
var q = numbers.map((n) => ++i);
q.forEach((v) =>
print("v = $v, i = $i"));
}
/*
v = 1, i = 1
v = 2, i = 2
v = 3, i = 3
v = 4, i = 4
v = 5, i = 5
v = 6, i = 6
v = 7, i = 7
v = 8, i = 8
v = 9, i = 9
v = 10, i = 10
*/
linq100(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var i = 0;
var q = numbers.map((n) => ++i).toList();
q.forEach((v) =>
print("v = $v, i = $i"));
}
/*
v = 1, i = 10
v = 2, i = 10
v = 3, i = 10
v = 4, i = 10
v = 5, i = 10
v = 6, i = 10
v = 7, i = 10
v = 8, i = 10
v = 9, i = 10
v = 10, i = 10
*/
linq101(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var lowNumbers = numbers
.where((n) => n <= 3);
print("First run numbers <= 3:");
lowNumbers.forEach(print);
for (int i = 0; i < 10; i++){
numbers[i] = -numbers[i];
}
print("Second run numbers <= 3:");
lowNumbers.forEach(print);
}
/*
First run numbers <= 3:
1
3
2
0
Second run numbers <= 3:
-5
-4
-1
-3
-9
-8
-6
-7
-2
0
*/