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Quickstart

Use the TimEL facade to compile and run a program:

// 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, so 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 simple case we are going to use a TreeMapVariable, which is a Variable backed by a regular in memory TreeMap: <code java> 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[][] {{0, 1, 1}, {1, 2, 2} /* Gap */, {2, 3, 4}}) values.put(Interval.of( now.plus(i[0], ChronoUnit.MINUTES), now.plus(i[1], ChronoUnit.MINUTES) ), i[2]); Compile “a * a” 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<Double> 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()); </code> That's it!

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  • Last modified: 2019/05/09 18:56
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