Concept and Grammar

Basic Concepts

Condition Primitive

• A condition primitive is a basic and built-in function which check some specified condition matched or not.

// return true if the request Host is "www.bfe-networks.com" or "bfe-networks.com"
req_host_in("www.bfe-networks.com|bfe-networks.com")

• BFE provides a set of built-in condition primitives

Condition Expression

• A condition expression is a series of condition primitives combined with operators (e.g. AND, OR, NOT, etc).

// return true if the request host is "bfe-networks.com" and the request method is "GET"
req_host_in("bfe-networks.com") && req_method_in("GET")

• The supported operators are described in another section below.

Grammar

Condition Primitive Grammar

A condition primitive is shown as follows:

func_name(params)

• func_name is the name of condition primitive
• params are the parameters condition primitive
• The type of return value is bool

Condition Expression Grammar

Condition Expression(CE) grammar is defined as follows:

CE = CE && CE
   | CE || CE
   | ( CE )
   | ! CE
   | ConditionPrimitive

Operator Precedence

The precedence and associativity of operators are similar to the C language. The following table lists the precedence and associativity of all operators. Operators are listed top to bottom, in descending precedence.

Precedence	Operator	Description	Associativity
1	()	parentheses (grouping)	Left-to-right
2	!	logical NOT	Right-to-left
3	&&	logical AND	Left-to-right
4	||	logical OR	Left-to-right