Groovy Series: Groovy Control Structures - Groovy Truth

//boolean expressions are used all over, so we first examine The Groovy Truth
//any type can be evaluated as a boolean expression, a few specialties:
 
//Boolean
assert true
 
//Matcher
assert ('Hello World' =~ /World/) //true because matcher has at least one match
 
//Collection
def numbers = [1,2,3]
assert numbers //true, as numbers in not empty
numbers = []
assert !numbers //numbers is now false, at it is an empty collection
 
//The same with maps, empty maps are false
assert ['one':1]
assert ![:]
 
//String 
assert 'This is true'
assert !''
 
//GStrings
def s = ''
assert !("$s") 
s = 'x'
assert ("$s") 
 
 
//Number
assert !0 //yeah, 0s are false, like in Perl
assert 1 //this is also true for all other number types
 
//Any object reference that is non-null is true!
assert new Object()
assert !null