Ruby class Constants parsing _ruby topics

A constant begins with a capital letter. It should be assigned up to one time. In the current version of Ruby, the re-assignment of constants produces only warnings rather than errors (the Non-ansi version of EVAL.RB does not report this warning)

Ruby>fluid=30
30
Ruby>fluid=31
31
Ruby>solid=32
32
Ruby>solid=33
(eval): 1:warning:already initialized constant Solid
33


Constants can be defined in classes, but unlike real variables, they can be accessed outside the class.

Ruby> class Constclass
| C1=101
| c2=102
| c3=103
| Def show
| Print C1, "", C2, "", C3, "\ n"
| End
| End
Nil
Ruby> C1
ERR: (eval): 1:uninitialized constant C1
Ruby> CONSTCLASS::C1
101
Ruby> ConstClass.new.show
101 102 103
Nil


Constants can also be defined in a module.

Ruby> Module Constmodule
| C1=101
| c2=102
| c3=103
| def showconstants
| Print C1, "", C2, "", C3, "\ n"
| End
| End
Nil
Ruby> C1
ERR: (eval): 1:uninitialized constant C1
Ruby> include Constmodule
Object
Ruby> C1
101
Ruby> showconstants
101 102 103
Nil
Ruby> c1=99 # Not really a good idea
99
Ruby> C1
99
Ruby> CONSTMODULE::C1 # The module ' s constant is undisturbed ...
101
Ruby> constmodule::c1=99
ERR: (eval): 1:compile error
(eval): 1:parse error
constmodule::c1=99
^
Ruby> constmodule::c1. Regardless of how we tamper with it.
101