When M syntax specifies a tvexpr, M evaluates the data as a numeric. However, it stops the evaluation and returns a true value (1) as soon as it encounters a non-zero digit, otherwise it returns a false value (0). In other words, M treats expressions that have a non-zero numeric value as true, and expressions that have a zero numeric value as false. The sign and/or decimal have no affect on the evaluation of a truth-valued expression.