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### 9.1 Predicates on Numbers

These functions return `t` if the specified condition is true of the numerical argument, or `nil` otherwise.

— Function: plusp number

> This predicate tests whether number is positive. It is an error if the argument is not a number.

— Function: minusp number

> This predicate tests whether number is negative. It is an error if the argument is not a number.

— Function: oddp integer

> This predicate tests whether integer is odd. It is an error if the argument is not an integer.

— Function: evenp integer

> This predicate tests whether integer is even. It is an error if the argument is not an integer.

— Function: floatp-safe object

> This predicate tests whether object is a floating-point number. On systems that support floating-point, this is equivalent to `floatp`. On other systems, this always returns `nil`.