Common Library (PQL)
Function Categories
These functions are used to perform calculations on dates and times. 

These functions represent some predefined formulas for formatting numbers and dates. 

These functions are used to perform derive details of the logged in user's identity and rights 

These functions are used for performing logical and conditional operations. 

These functions are used for performing mathematical functions and operations 

These functions are used for performing statistical and aggregate functions and operations 

These functions are used for manipulating text strings. 
Overview
Common functions are a set of methods that are found in most programmatic and mathematical function libraries. These functions are used to perform logic on basic data without concern for data structures, context, or even source. As such they can run almost anywhere and are common to all parts of the calculation engine.
The Common library includes numerous methods for handling math, dates, strings and logical flows. It also includes a collection of functions that will help developers identify Pyramid users (and their details) plus methods for strengthening the calculation power of the other parts of the calculation engine.
Common calculations are usually done with standard libraries found in Java, C#, VB, VBA and C++.