This is a Ruby tree! It shows every object from the Ruby Programming Language in a tree format.

[]= 

        # String.[]=

(from ruby core)
---
    str[integer] = new_str
    str[integer, integer] = new_str
    str[range] = aString
    str[regexp] = new_str
    str[regexp, integer] = new_str
    str[regexp, name] = new_str
    str[other_str] = new_str

---

Element Assignment---Replaces some or all of the content of *str*. The
portion of the string affected is determined using the same criteria as
String#[]. If the replacement string is not the same length as the text
it is replacing, the string will be adjusted accordingly. If the regular
expression or string is used as the index doesn't match a position in
the string, IndexError is raised. If the regular expression form is
used, the optional second Integer allows you to specify which portion of
the match to replace (effectively using the MatchData indexing rules.
The forms that take an Integer will raise an IndexError if the value is
out of range; the Range form will raise a RangeError, and the Regexp and
String will raise an IndexError on negative match.

This is MURDOC! A Ruby documentation browser inspired by Smalltalk-80. It allows you to learn about Ruby by browsing through its class hierarchies, and see any of its methods.