Screening Rule Operators

Operators

Operators are of two types:

• Binary operators join two functions.
  
• Unary operators operate on a single function.
  


&& is the binary operator "and". For example,


Find(“interest rate”) && Find(“APR”,false)

matches a message only if it includes both "interest rate" and "APR."



|| is the binary operator "or." For example,


Find(“station wagon”) || Find(“convertible”)

matches any message that includes either "station wagon" or "convertible" (or "Station Wagon" or "station Wagon" or "Convertible").



! is the unary operator "not." For example,


!Find(“windows”)

matches any message that does not include the word "windows."


You can combine ! with a binary operator. For example,


Find(“bird”) && !Find(“goose”)

matches any message that includes "bird" but does not include "goose."


Operator Precedence

p && q || r is parsed as (p && q) || r. For example, consider:


Find(“debt”) && Find(“income”) || Find(“profit”)

To paraphrase, this screening rule is basically “find X or find Y,” where X is "debt" and "income," and Y is "profit."
It matches both "debt exceeds income" and "profits are fantastic".


You can modify the default precedence by the explicit use of parentheses; for example:


Find(“debt”) && (Find(“income”) || Find(“profit”))

This screening rule is basically “find X and find Y,” where X is "debt" and Y is either "income" or "profit."
It matches both "debt exceeds income" and "debts impact profit."