# `BadBooleanError`
[🔗](https://github.com/elixir-lang/elixir/blob/v1.20.0-rc.3/lib/elixir/lib/exception.ex#L1483)

An exception raised when a boolean is expected, but something else was given.

This exception is raised by `and` and `or` when the first argument is not a boolean:

    iex> 123 and true
    ** (BadBooleanError) expected a boolean on left-side of "and", got:
    ...

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*Consult [api-reference.md](api-reference.md) for complete listing*