diff --git a/README.md b/README.md
index f493b02..19458c3 100644
--- a/README.md
+++ b/README.md
@@ -345,6 +345,12 @@ This crate offers a set of builtin functions.
 | `round`              | 1               | Numeric                | Returns the nearest integer to a number. Rounds half-way cases away from 0.0 |
 | `ceil`               | 1               | Numeric                | Returns the smallest integer greater than or equal to a number |
 | `if`                 | 3               | Boolean, Any, Any      | If the first argument is true, returns the second argument, otherwise, returns the third  |
+| `if`                 | 3               | Boolean, Any, Any      | If the first argument is true, returns the second argument, otherwise, returns the third  |
+| `is_nan`             | 1               | Numeric                | Returns true if the argument is the floating-point value NaN, false otherwise  |
+| `is_finite`          | 1               | Numeric                | Returns true if the argument is a finite floating-point number, false otherwise  |
+| `is_infinite`        | 1               | Numeric                | Returns true if the argument is an infinite floating-point number, false otherwise  |
+| `is_normal`          | 1               | Numeric                | Returns true if the argument is a floating-point number that is neither zero, infinite, subnormal, or NaN, false otherwise  |
+| `is_subnormal`       | 1               | Numeric                | Returns true if the argument is a [subnormal](https://en.wikipedia.org/wiki/Subnormal_number) number, false otherwise  |
 | `math::ln`           | 1               | Numeric                | Returns the natural logarithm of the number |
 | `math::log`          | 2               | Numeric, Numeric       | Returns the logarithm of the number with respect to an arbitrary base |
 | `math::log2`         | 1               | Numeric                | Returns the base 2 logarithm of the number |