Short Haskell applications: text, numbers, treesort and DFAs

3rd CCSC Northwest Conference • Fall 2001

Short Haskell applications: text, numbers, treesort and DFAs

Simple text processing

higher-order list functions and a few simple utilities can be combined to do simple text processing

3rd CCSC Northwest Conference • Fall 2001

Short Haskell applications: text, numbers, treesort and DFAs

Simple text processing

ROT-13 transcoder

similar techniques allow us to define a basic "ROT-13" text encryption utility in about 5 lines

3rd CCSC Northwest Conference • Fall 2001

Short Haskell applications: text, numbers, treesort and DFAs

Simple text processing

ROT-13 transcoder

Command-line interaction

Haskell's pre-defined interaction process is based on whole inputs, but a few intervening functions allow us to easily define a line-by-line user interaction program

3rd CCSC Northwest Conference • Fall 2001

Short Haskell applications: text, numbers, treesort and DFAs

Simple text processing

ROT-13 transcoder

Command-line interaction

Palindrome checking

we can check whether a string is a palindrome by normalizing it and comparing it to its own reversal: the palindrome checker

3rd CCSC Northwest Conference • Fall 2001

Short Haskell applications: text, numbers, treesort and DFAs

Simple text processing

ROT-13 transcoder

Command-line interaction

Palindrome checking

Numeral conversion in different bases

by spotting certain symmetries in base-radix notation, we can easily write "generator functions" for arbitrary number bases which convert between strings and integers

3rd CCSC Northwest Conference • Fall 2001

Short Haskell applications: text, numbers, treesort and DFAs

Simple text processing

ROT-13 transcoder

Command-line interaction

Palindrome checking

Numeral conversion in different bases

Binary trees and treesort

a data type for binary search trees, plus an appropriate fold function over those trees, makes the definition of tree sort clear and compelling

3rd CCSC Northwest Conference • Fall 2001

Short Haskell applications: text, numbers, treesort and DFAs

Simple text processing

ROT-13 transcoder

Command-line interaction

Palindrome checking

Numeral conversion in different bases

Binary trees and treesort

DFA simulation

we can transcribe a definition of deterministic finite automata almost verbatim from a theory text, and then experiment with automata and strings

	Simple text processing
	ROT-13 transcoder similar techniques allow us to define a basic "ROT-13" text encryption utility in about 5 lines

	Simple text processing
	ROT-13 transcoder
	Command-line interaction Haskell's pre-defined interaction process is based on whole inputs, but a few intervening functions allow us to easily define a line-by-line user interaction program

	Simple text processing
	ROT-13 transcoder
	Command-line interaction
	Palindrome checking we can check whether a string is a palindrome by normalizing it and comparing it to its own reversal: the palindrome checker