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Subsections

- Bro Types
- Type Conversions

# Overview

We begin with an overview of the types of values supported by Bro, giving a brief description of each type and introducing the notions of type conversion and type inference. We discuss each type in detail in § 3.2-§ 3.17 below.

## Bro Types

There are 18 types of values in the Bro type system:

- `bool` for Booleans;

- `count`, `int`, and `double` types, collectively called numeric, for arithmetic and logical operations, and comparisons;

- `enum` for enumerated types similar to those in C;

- `string`, character strings that can be used for comparisons and to index tables and sets;

- `pattern`, regular expressions that can be used for pattern matching;

- `time` and `interval`, for absolute and relative times, collectively termed temporal;

- `port`, a TCP or UDP port number;

- `addr`, an IP address;

- `net`, a network prefix;

- `record`, a collection of values (of possibly different types), each of which has a name;

- `table`, an associative array, indexed by tuples of scalars and yielding values of a particular type;

- `set`, a collection of tuples-of-scalars, for which a particular tuple's membership can be tested;

- `file`, a disk file to write or append to;

- `function`, a function that when called with a list of values (arguments) returns a value;

- `event`, an event handler that is invoked with a list of values (arguments) any time an event occurs.

Every value in a Bro script has one of these types. For most types there are ways of specifying constants representing values of the type. For example, `2.71828` is a constant of type `double`, and `80/tcp` is a constant of type `port`. The discussion of types in § 3.2-§ 3.17 below includes a description of how to specify constants for the types.

Finally, even though Bro variables have static types, meaning that their type is fixed, often their type is inferred from the value to which they are initially assigned when the variable is declared. For example,

        local a = "hi there";

fixes `a`'s type as `string`, and

        local b = 6;

sets `b`'s type to `count`. See § for further discussion.

##
Type Conversions

Some types will be automatically converted to other types as needed. For example, a `count` value can always be used where a `double` value is expected. The following:

        local a = 5;
        local b = a * .2;

creates a local variable `a` of type `count` and assigns the `double` value `1.0` to `b`, which will also be of type `double`. Automatic conversions are limited to converting between numeric types. The rules for how types are converted are given below.

Next: Booleans Up: Values, Types, and Constants Previous: Values, Types, and Constants Contents Index