				Pico + Pool: A Layered Programming Approach
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Pico, Pool, and Isar
	Pico: Lisp interpreter based on simple data structures
	Pool: Pico object oriented lisp
		Object oriented extensions to Pico
	Isar: Interactive Station for Assembly and Retouch
		A layout-design system implemented in Pool
Short History
	Pico: Tool to enhance my own productivity
	Enter G&R
	Extend Pico during development of Isar
	Pool: Add object oriented extensions
	Isar -> object oriented
Advantages of an Interpreted Environment
	Immediate access to all parts of the system
	Browsing, Prototyping, Debugging
	Modify program while running
Advantages of using Lisp
	Flexible data structures
	Automatic memory management
		Everything is dynamic, no declarations
		Variable length data structures
		Incremental garbage collection
		Dynamic memory objects
	Identical representation for code and data
		Easy to write software tools
		Expressive programming style using functional application
Advantages of using Pico Lisp
	Access to all Programming layers
		Toolbox,C,Pico,Pool,PicApp
	Easy to customize for special-purpose applications
	Speed is ok if low level parts are in C
	Acceptable size with zap,comsex and remob
	No access to source in end user version
	No licence problems with interpreter kernel
	Portable to other machine or OS if
		Memory organized in bytes
		Pointers and long words 32 bit

Developing with less stress
	Clear project design with object orientation
	Simplicity on each layer
	No need for a priori decisions (declarations)
	No fear of repeated code

Drawbacks
	Difficult to learn
		Kernel: 605 C-functions,  89 Lisp-functions
		Isar:   639 C-functions, 482 Lisp-functions, 216 Methods
	Low execution speed of parts that are not written in C
	Needs more memory than an application written completely in C
