# Idiom # 86: Check if integer multiplication will overflow

## Code

For all integers with wrap-around semantics (i.e. all the standard types i32,
u64, etc.), there are two ways to check for overflow on multiplication. First,
the predicate `overflow_on_mul`

checks if a multiplication of two
values would overflow. Next, there is a multiplication operator ```
infix
*?
```

that performs overflow checking and returns a `num_option`

that can be checked afterwards.

Note that `infix *`

would result in a runtime error in case of an
overflow if debug checks are enabled. If overflow semantics are desired,
operator `infix *°`

has to be used.