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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, 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[][] {{0 /* start */, 1 /* end */, 1 /* value */}, {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" 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!

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  • Last modified: 2019/05/09 19:02
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