On this page

End of Life Ruby 3.2 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →

class · Ruby 3.2

PrettyPrint

< Object 9 instance methods 3 class methods

This class implements a pretty printing algorithm. It finds line breaks and nice indentations for grouped structure.

By default, the class assumes that primitive elements are strings and each byte in the strings have single column in width. But it can be used for other situations by giving suitable arguments for some methods:

newline object and space generation block for PrettyPrint.new
optional width argument for PrettyPrint#text
PrettyPrint#breakable

There are several candidate uses:

text formatting using proportional fonts
multibyte characters which has columns different to number of bytes
non-string formatting

Bugs

Box based formatting?
Other (better) model/algorithm?

Report any bugs at bugs.ruby-lang.org

References

Christian Lindig, Strictly Pretty, March 2000, www.st.cs.uni-sb.de/~lindig/papers/#pretty

Philip Wadler, A prettier printer, March 1998, homepages.inf.ed.ac.uk/wadler/topics/language-design.html#prettier

Author

Tanaka Akira <[email protected]>

Class methods 3

.format .new .singleline_format

Instance methods 9

#breakable #break_outmost_groups #current_group #fill_breakable #flush #group #group_sub #nest #text

Attributes

genspace

Read

A lambda or Proc, that takes one argument, of an Integer, and returns the corresponding number of spaces.

By default this is:

Example

lambda {|n| ' ' * n}

group_queue

Read

The PrettyPrint::GroupQueue of groups in stack to be pretty printed

indent

Read

The number of spaces to be indented

maxwidth

Read

The maximum width of a line, before it is separated in to a newline

This defaults to 79, and should be an Integer

newline

Read

The value that is appended to output to add a new line.

This defaults to “\n”, and should be String

output

Read

The output object.

This defaults to ”, and should accept the << method