What are the restrictions for method names in Ruby?

Question

For example, I found the method name bundler? in the following snippet, and don\'t know whether the ? character is a specialized keyword or just pa

Answer 1

What others say is true for the built-in syntax, however there seems to be no back-end restrictions on what can be used if you use methods like define_method + send:

define_method(:'$% ^&') { 0 }
define_method(:'你好') { 1 }

send(:'$% ^&') == 0 or raise
send(:'你好') == 1 or raise

This fact can be useful: for example Rails' ActiveSupport::Testing::Declarative.test method uses it so as not to do complex conversions on:

test 'Some Controller#Method' do

to a saner name, which might conflict with another test named:

test 'Some Controller_Method' do

This is mentioned on the Testing Guide.

Curiosity: a similar thing happens in Java, where the bytecode method name gives way more choice than the Java language: Why does the JVM allow us to name a function starting with a digit in bytecode?