Lecture Notes for Advanced Programming II

8 February 2001 - Libraries and Interface Design

1. libraries and interfaces

   1. repetition is the mother of libraries

   2. desirable library features

      1. it works - a broken library is useless

      2. easy to learn - write my own

      3. easy to use - ditto

      4. costs less than benefits - conceptual, programming, and execution costs

      5. stability - no changes

   3. issues

      1. function - what does the library do

      2. detail - how much do i have to know

      3. resource management - who's responsible for what

      4. error handling -

2. discovering libraries

   1. if you do something more than one time, write a library for it - command-line argument parsing; printing error messages; establishing and using network connections; variable-length lists of memory blocks

   2. data formats - comma separated lists

3. prototypes and experimentation

   1. good libraries don't appear, they evolve

   2. prototyping is one approach - particularly at the start

   3. use and change - early on; stability

   4. anticipate or avoid changes - simplify function; extend generality; improve performance; fix errors

   5. increasing use freezes libraries

4. durable libraries

   1. function (interface) - simple, complete functions

   2. information hiding - the more the better; change resistance; protection

   3. resource management - memory, files

   4. error handling - a big problem; knowledge vs recovery

   5. documentation - all this has to be documented

5. c++ library design

   1. the wrapper pattern - a way to unify libraries

   2. multiple inheritance, abstract virtual classes, and interfaces

6. principles

   1. information hiding - the more the better; safety, change; no globals

   2. small, well defined purpose - easy to understand; most combinations make some sense; narrow interfaces

   3. no surprises - performance; resources; errors; data

   4. follow conventions consistently - copying and assignment; indexing from 0

7. resource management

   1. resource management is important, but who should do it

   2. resources - memory; open files; shared state

   3. initialize, manipulate, share and copy, decommission

   4. information hiding helps answer a lot of these questions

   5. whatever makes it unmakes it

8. errors

   1. low-level detection, high-level recovery

   2. exceptions are exceptionally bad

   3. explicit routines for dealing with errors - tends to get complicated quickly

9. user-interface design

   1. you don't know jack - there are some rules about what not to do

   2. prototype, prototype, prototype

   3. review, test, and review...

This page last modified on 8 February 2001.