Why does the [removed]true == true == true) produce a syntax error?

Question

Ruby:

true == true == true

syntax error, unexpected tEQ

Answer 1

Association direction, which controls the order of operators having their arguments evaluated, is not defined for the == method, same as for ===, !=, =~ and <=> methods as well (all of which have the same precedence and form a separate precedence group exclusively).

Documentation

Thus evaluation order in case of multiple operators from the list mentioned above being chained in a row should be set explicitly via either

• parenthesis ():

  (true == true) == true # => true
  true == (true == true) # => true
  

• or dot operator . (can be omitted for the last equality check in a row):

  true .== true == true # => true