Feature #17210: More readable and useful `Set#inspect`

• Status: Closed
• Assignee: knu (Akinori MUSHA)
• Target version: -

[marcandre (Marc-Andre Lafortune)]

I would like to change Set#inspect/to_s:

# before
puts Set[1,2,3] # => "#<Set: {1, 2, 3}>"

# after
puts Set[1,2,3] # => "Set[1, 2, 3]"

This output is shorter, readable, and has the property that it corresponds to Ruby code

[zverok (Victor Shepelev)]

BTW, as a side note, it would be good to have some "style guide" for inspect behavior in Ruby. Ad-hoc rule seem to be #<ClassName some representation of content> most of the time, except for objects that have corresponding literals -- they are just represented by literals. But:

• how the "content" should be represented, is not always consistent from class to class: #<struct A a=1, b=2>, #<Date: 2020-10-02 ((2459125j,0s,0n),+0s,2299161j)>, #<Set: {1, 2, 3}>, #<OpenStruct a=1, b=2>, #<Enumerator: [1, 2, 3]:map>, <File:README.md>, #<CSV::Row "Name":"Bob" "Department":"Engineering" "Salary":"1000">
• of core objects, say, the Time is breaking all conventions being represented as 2020-10-02 12:10:51 +0300 -- which even doesn't look as one atomic entity
• of all stdlib I've checked, only matrix does similar to proposed: Matrix[[25, 93], [-1, 66]], Vector[1, 2], so it is a bit unusual for #inspect, though it is not necessary a bad thng

[universato (Yoshimine Sato)]

+1
I second the proposal.

p [1, 2, 3] #=> [1, 2, 3]
p "hello"   #=> "hello"
p 1.0       #=> 1.0
p({"x"=>1}) #=> {"x"=>1}
p 1..2      #=> 1..2
p nil       #=> nil
p true      #=> true
p :name     #=> :name
p Array     #=> Array

require "matrix"
p Matrix[[1, 2], [3, 4]] #=> Matrix[[1, 2], [3, 4]]
p Vector[1, 2]           #=> Vector[1, 2]

The output of the major classes equal to Ruby code(literal or syntax sugar).
It is very useful and readable.

[hsbt (Hiroshi SHIBATA)]

• Status changed from Open to Assigned

[hsbt (Hiroshi SHIBATA)]

• Status changed from Assigned to Closed

❯ ruby -ve "puts Set[1,2,3]"
ruby 4.1.0dev (2026-01-06T23:05:30Z master b2ed4cdced) +YJIT +MN +PRISM [arm64-darwin25]
Set[1, 2, 3]

Ruby 4.0 introduced this feature request.