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Class: RuboCop::Cop::Lint::FloatComparison

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::RuboCop::Cop::Base, ::RuboCop::ExcludeLimit, NodePattern::Macros, RuboCop::AST::Sexp
Instance Chain:
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/lint/float_comparison.rb

Overview

Checks for the presence of precise comparison of floating point numbers.

Floating point values are inherently inaccurate, and comparing them for exact equality is almost never the desired semantics. Comparison via the ==/!= operators checks floating-point value representation to be exactly the same, which is very unlikely if you perform any arithmetic operations involving precision loss.

# good - comparing against zero
 x == 0.0
 x != 0.0
# good
(x - 0.1).abs < Float::EPSILON
# good
tolerance = 0.0001
(x - 0.1).abs < tolerance
# Or some other epsilon based type of comparison:
# https://www.embeddeduse.com/2019/08/26/qt-compare-two-floats/

Examples:

# bad
x == 0.1
x != 0.1

# good - using BigDecimal
x.to_d == 0.1.to_d

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

Class Attribute Summary

::RuboCop::Cop::Base - Inherited

.gem_requirements, .lint?,
.support_autocorrect?

Returns if class supports autocorrect.

.support_multiple_source?

Override if your cop should be called repeatedly for multiple investigations Between calls to on_new_investigation and on_investigation_end, the result of processed_source will remain constant.

Class Method Summary

::RuboCop::Cop::Base - Inherited

.autocorrect_incompatible_with

List of cops that should not try to autocorrect at the same time as this cop.

.badge

Naming.

.callbacks_needed, .cop_name, .department,
.documentation_url

Returns an url to view this cops documentation online.

.exclude_from_registry

Call for abstract Cop classes.

.inherited,
.joining_forces

Override and return the Force class(es) you need to join.

.match?

Returns true if the cop name or the cop namespace matches any of the given names.

.new,
.requires_gem

Register a version requirement for the given gem name.

.restrict_on_send

::RuboCop::ExcludeLimit - Extended

exclude_limit

Sets up a configuration option to have an exclude limit tracked.

transform

Instance Attribute Summary

Instance Method Summary

::RuboCop::Cop::Base - Inherited

#add_global_offense

Adds an offense that has no particular location.

#add_offense

Adds an offense on the specified range (or node with an expression) Unless that offense is disabled for this range, a corrector will be yielded to provide the cop the opportunity to autocorrect the offense.

#begin_investigation

Called before any investigation.

#callbacks_needed,
#cop_config

Configuration Helpers.

#cop_name, #excluded_file?,
#external_dependency_checksum

This method should be overridden when a cop’s behavior depends on state that lives outside of these locations:

#inspect
#message

Gets called if no message is specified when calling add_offense or add_global_offense Cops are discouraged to override this; instead pass your message directly.

#name

Alias for Base#cop_name.

#offenses,
#on_investigation_end

Called after all on_…​

#on_new_investigation

Called before all on_…​

#on_other_file

Called instead of all on_…​

#parse

There should be very limited reasons for a Cop to do it’s own parsing.

#parser_engine,
#ready

Called between investigations.

#relevant_file?, #target_rails_version, #target_ruby_version, #annotate, #apply_correction, #attempt_correction,
#callback_argument

Reserved for Cop::Cop.

#complete_investigation

Called to complete an investigation.

#correct, #current_corrector,
#current_offense_locations

Reserved for Commissioner:

#current_offenses, #currently_disabled_lines, #custom_severity, #default_severity, #disable_uncorrectable, #enabled_line?, #file_name_matches_any?, #find_message, #find_severity, #range_for_original, #range_from_node_or_range,
#reset_investigation

Actually private methods.

#use_corrector

::RuboCop::Cop::AutocorrectLogic - Included

::RuboCop::Cop::IgnoredNode - Included

Constructor Details

This class inherits a constructor from RuboCop::Cop::Base

Instance Method Details

#check_numeric_returning_method(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/lint/float_comparison.rb', line 91

def check_numeric_returning_method(node)
  return false unless node.receiver

  case node.method_name
  when :angle, :arg, :phase
    Float(node.receiver.source).negative?
  when :ceil, :floor, :round, :truncate
    precision = node.first_argument
    precision&.int_type? && Integer(precision.source).positive?
  end
end

#check_send(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/lint/float_comparison.rb', line 75

def check_send(node)
  if node.arithmetic_operation?
    lhs, _operation, rhs = *node
    float?(lhs) || float?(rhs)
  elsif FLOAT_RETURNING_METHODS.include?(node.method_name)
    true
  elsif node.receiver&.float_type?
    if FLOAT_INSTANCE_METHODS.include?(node.method_name)
      true
    else
      check_numeric_returning_method(node)
    end
  end
end

#float?(node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/lint/float_comparison.rb', line 53

def float?(node)
  return false unless node

  case node.type
  when :float
    true
  when :send
    check_send(node)
  when :begin
    float?(node.children.first)
  else
    false
  end
end

#literal_zero?(node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/lint/float_comparison.rb', line 68

def literal_zero?(node)
  # TODO: https://github.com/rubocop/rubocop-ast/pull/304 is released,
  # replace this condition with `node&.numeric_type? && node.value.zero?`.
  node&.numeric_type? && node.node_parts[0].zero?
end

#on_send(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/lint/float_comparison.rb', line 44

def on_send(node)
  lhs, _method, rhs = *node
  return if literal_zero?(lhs) || literal_zero?(rhs)

  add_offense(node) if float?(lhs) || float?(rhs)
end