### 25.2.4 Checking required conditions

The assert command breaks out of a function with an error.

- assert takes bool, a boolean.
- assert(bool) does nothing if bool is true, it returns from the function with an error if bool is false.

#### Example

Define the function:

sqofpos(x):={ assert(x>0); return x^2; }

then:

sqofpos(4)

16 |  |  |  |  |  |  |  |  |  |

sqofpos(-4)

“assert failure: x>0 Error: Bad Argument Value” |  |  |  |  |  |  |  |  |  |

since −4>0 is false.