[ruby-talk:444085] Re: A simple question about arguments

def tt (x=123) puts x end => :tt

tt 123 => nil

tt(456) 456 => nil

The code above is the default argument I know. But this one,

def tt2 (x:123) puts x 1> end => :tt2

tt2 123 => nil

tt2(456) Traceback (most recent call last): 5: from /usr/bin/irb:23:in `<main>' 4: from /usr/bin/irb:23:in `load' 3: from /Library/Ruby/Gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top (required)>' 2: from (irb):10 1: from (irb):6:in `tt2' ArgumentError (wrong number of arguments (given 1, expected 0))

As you see it fails. But the following calling could work.

tt2(x:456) 456 => nil

tt2(:x=>456) 456 => nil

what's the trick behind it? Thanks & regards, Henry