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Quickstart

To use TimEL you need to import the following dependecy:

Maven

<dependency>
    <groupId>net.vleo.timel</groupId>
    <artifactId>timel-core</artifactId>
    <version>0.9.1</version>
</dependency>

Gradle

implementation 'net.vleo.timel:timel-core:0.9.1'


When the dependency is in place, use the TimEL facade class to compile and evaluate expressions:

// Assemble the evaluation interval as [now, now + 1 second)
Instant now = Instant.now();
Interval interval = Interval.of(now, now.plus(1, ChronoUnit.SECONDS));
 
// Compile the expression 1 + 1.
// As we expect an Integer here, we explicitly request an IntegerType
// for the sake of type safety, but we can compile generic code as well.
Expression<Integer> expression = TimEL
        .parse("1 + 1")
        .compile(new IntegerType());
 
// Iterate through the results
TimeIterator<Integer> itor = TimEL
        .evaluate(expression, interval);
 
// Since 1+1 is constant we'll have a single sample for the whole interval
int v = itor.next().getValue();

That's it!


Now let's try something a bit more complex, where we provide an input time-serie variable. As TimEL is a streaming api, it will pull values out of the variable when it needs them. In this case we are going to use a TreeMapVariable, which is a Variable backed by a regular in memory TreeMap:

// Create a new variable backed by a TreeMap
TreeMapVariable<Integer> variable = new TreeMapVariable<>();
TreeMap<Interval, Integer> values = variable.getTreeMap();
 
// Add some values to the variable
Instant now = Instant.now();
for(int[] i : new int[][] {
        // start, end, value
        {0, 1, 1},
        {1, 2, 2},
        // gap between 2nd and 3rd minute
        {3, 4, 4}
 }) {
    values.put(Interval.of(
            now.plus(i[0], ChronoUnit.MINUTES),
            now.plus(i[1], ChronoUnit.MINUTES)
    ), i[2]);
}
 
// Compile "a * a" without type requirement
Expression<?> expression = TimEL
        .parse("a * a")
        .withVariable("a", new IntegerType(), variable) // Declare 'a' as a int
        .compile();
 
// Evaluate the expression in the interval [now, now + 5 minutes)
TimeIterator<?> itor = TimEL
        .evaluate(expression, Interval.of(now, now.plus(5, ChronoUnit.MINUTES)));
 
// Pull the results, effectively evaluating the expression.
// This will print 3 lines, one for each interval, with the value 1, 4 and 16.
while(itor.hasNext())
    System.out.println("\t" + itor.next());

That's it!

  • quickstart.1558123996.txt.gz
  • Last modified: 2019/05/17 20:13
  • by a.leofreddi