Count value in template expression

I want to count a value inside a template expression, in Xtend, without printing it out.

This is my code:

def generateTower(Tower in) {
    var counter = 0.0;
'''
One         Two             Three           Four
«FOR line : in.myTable»
«counter»   «line.val1»     «line.val2»     «line.val3»
«counter = counter + 1»
«ENDFOR»
'''
    }

So this will generate a table with four columns, whereas the first column is incremented starting at 0.0. The problem is, that «counter = counter + 1» is printed as well. But I want the expression above to just count up, without printing it out.

What could be the best solution to solve this problem?

You could use this simple and readable solution:

«FOR line : in.myTable»
«counter++»   «line.val1»     «line.val2»     «line.val3»
«ENDFOR»

If you insist on the separate increment expression, use a block with null value. This works because the null value is converted to empty string in template expressions (of course you could use "" as well):

«FOR line : in.myTable»
«counter»   «line.val1»     «line.val2»     «line.val3»
«{counter = counter + 1; null}»
«ENDFOR»

Although the first solution is the better. If you require complex logic in a template expression I recommend implementing it by methods not by inline code...

And finally, here is a more OO solution for the problem:

class TowerGenerator {
    static val TAB = "\t"

    def generateTower(Tower in) {
        var counter = 0

        '''
            One«TAB»Two«TAB»Three«TAB»Four
            «FOR line : in.myTable»
                «generateLine(line, counter++)»
            «ENDFOR»
        '''
    }

    def private generateLine(Line line, int lineNumber) '''
        «lineNumber»«TAB»«line.val1»«TAB»«line.val2»«TAB»«line.val3»
    '''
}