# File lib/puppet/parser/ast/minus.rb, line 14
14:     def evaluate(scope)
15:       val = @value.safeevaluate(scope)
16:       val = Puppet::Parser::Scope.number?(val)
17:       if val == nil
18:         raise ArgumentError, "minus operand #{val} is not a number"
19:       end
20:       -val
21:     end