text: +++
  title = "`bool has_error() const noexcept`"
  description = "Returns true if an error is present. Constexpr, never throws."
  categories = ["observers"]
  weight = 592
  +++
  
  Returns true if an error is present. Constexpr where possible.
  
  *Requires*: Always available.
  
  *Complexity*: Constant time.
  
  *Guarantees*: Never throws an exception.
  