Class: Hone::Patterns::SortFirst

Inherits:
Base
  • Object
show all
Defined in:
lib/hone/patterns/sort_first.rb

Overview

Pattern: array.sort.first -> array.min, array.sort.last -> array.max

sort.first/last sorts the entire array O(n log n) then takes one element. min/max finds the element in a single O(n) pass without sorting.

Instance Attribute Summary

Attributes inherited from Base

#findings

Instance Method Summary collapse

Methods inherited from Base

#add_finding, inherited, #initialize, scan_file

Constructor Details

This class inherits a constructor from Hone::Patterns::Base

Instance Method Details

#visit_call_node(node) ⇒ Object 



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# File 'lib/hone/patterns/sort_first.rb', line 13

def visit_call_node(node)
  super

  return unless %i[first last].include?(node.name) && node.arguments.nil?

  receiver = node.receiver
  return unless receiver.is_a?(Prism::CallNode)

  case [receiver.name, node.name]
  when [:sort, :first]
    add_finding(
      node,
      message: "Use `.min` instead of `.sort.first` to find minimum in O(n) without sorting",
      speedup: "O(n log n) sort to O(n) single pass, no intermediate array"
    )
  when [:sort, :last]
    add_finding(
      node,
      message: "Use `.max` instead of `.sort.last` to find maximum in O(n) without sorting",
      speedup: "O(n log n) sort to O(n) single pass, no intermediate array"
    )
  when [:sort_by, :first]
    return unless block_attached?(receiver)
    add_finding(
      node,
      message: "Use `.min_by { }` instead of `.sort_by { }.first` to find minimum in O(n)",
      speedup: "O(n log n) sort to O(n) single pass, no intermediate array"
    )
  when [:sort_by, :last]
    return unless block_attached?(receiver)
    add_finding(
      node,
      message: "Use `.max_by { }` instead of `.sort_by { }.last` to find maximum in O(n)",
      speedup: "O(n log n) sort to O(n) single pass, no intermediate array"
    )
  end
end