Groovy has a broader sence of what is true or false than the boolean expressions. For example an empty list or string is false in Groovy. This makes that we can write less code in conditional expressions to evaluate true or false:
// Booleans: def b1 = false def b2 = true assert !b1 assert b2 // Strings: def s1 = '' def s2 = 'abc' assert !s1 assert s2 // Numbers: def n1 = 0 def n2 = 42 assert !n1 assert n2 // Lists, iterators: def l1 = [] def l2 = [1, 3, 6] assert !l1 assert l2 def i1 = l1.iterator() def i2 = l2.iterator() assert !i1 assert i2 // Maps: def m1 = [:] def m2 = ['key': 'value'] assert !m1 assert m2 // Objects: def o1 def o2 = new Expando(name: 'groovy') assert !o1 assert o2 // Matchers: def ma1 = "groovy" =~ /java/ def ma2 = "groovy" =~ /groovy/ assert !ma1 assert ma2
