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- Notes
### Notes

## -INF, INF, NAN, Try evaluation error!

This may seem surprising but, for example, {= log(0)} and x = log(0); are two very different things in the Formulas question.

{= log(0)} is computed by PHP without implying any variable and, according to PHP rules, the result is -INF. With x = log(0);, this value is assigned to x and must therefore be one of the variable types of the Formulas question: number, string, list of numbers, list of strings or algebraic variable. -INF does not belong to any of these types, so x = log(0); is not accepted and the message "Try evaluation error!" will appear in the Formulas question's edit page.

If you try x = INF;, the question Formulas will indicate that INF has not been defined, as if INF was the name of another variable. x = is_infinite(log(0)); is correct and will define x as 1 (true).

### References