Skip to main content

W0025 - Boolean Precedence

Warning​

foo(X) ->
  predicate(X) or X > 10.
%%             ^^ 💡 warning: Consider using the short-circuit expression 'orelse' instead of 'or'.
%%              | Or add parentheses to avoid potential ambiguity.

Explanation​

The and/or operands have higher precedence than comparison ops (unlike andalso/orelse) so this could be a source of bugs.

17> F = fun(X) -> is_integer(X) and X > 0 end.
#Fun<erl_eval.42.105768164>
18> F(-1).
** exception error: bad argument
     in operator  and/2
        called as true and -1

Note that changing this may affect the semantics, as and/or always evaluate both arguments, so guarantee any side-effects in those computations take place. In contrast, andalso/orelse do short circuit evaluation so may not execute the RHS of the expression.

If it is necessary to use and/or, you can preceed the expression with a special comment to silence the linter:

% elp:ignore W0025 - An optional explanation here