EC
Math::DomainError
RubyERRORNotableMath

Math function input outside its domain

Quick Answer

Clamp or validate numeric inputs before calling Math module functions.

What this means

Raised by functions in the Math module when a numeric argument falls outside the mathematical domain of the function. It is a subclass of ArgumentError and distinct from FloatDomainError.

Why it happens
  1. 1Math.asin or Math.acos called with a value outside [-1, 1]
  2. 2Math.log called with a non-positive value
  3. 3Math.sqrt called with a negative Float

Fix

Clamp input for asin/acos

Clamp input for asin/acos
def safe_acos(x)
  Math.acos(x.clamp(-1.0, 1.0))
end

Why this works

Clamping ensures floating-point rounding errors near -1 or 1 do not push the value out of domain.

Code examples
acos out of domainruby
Math.acos(1.0001)
# Math::DomainError: Numerical argument is out of domain - "acos"
Rescue Math::DomainErrorruby
begin
  angle = Math.acos(value)
rescue Math::DomainError
  angle = 0.0
end
Checking ancestryruby
Math::DomainError < ArgumentError  # => true
Math::DomainError < StandardError  # => true
Sources
Official documentation ↗

Ruby Core Documentation

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