RERE.Examples

Various examples of using rere, as used in the blog post.

Documentation

>>> import Test.QuickCheck.Random (mkQCGen)
>>> import Test.QuickCheck.Gen (unGen)
>>> import Control.Monad.ST (runST)
>>> import RERE
>>> let runGen seed = maybe "<<null>>" (\g' -> unGen g' (mkQCGen seed) 10)
>>> let showRef re = matchDebugR re ""

Syntax

syntaxExamples :: IO ()

Demonstrates how various constructors are pretty printed.

Example 1

ex1 :: RE Void

>>> match ex1 "abab"
True

>>> match ex1 "ababa"
False

>>> ex1
Star (App (Ch "a") (Ch "b"))

>>> charClasses ex1
fromList "\NULabc"

>>> showRef ex1
size: 4
show: Star (App (Ch "a") (Ch "b"))
null: True

>>> matchR ex1 "abab"
True

>>> matchR ex1 "ababa"
False

>>> runGen 43 (generate 10 20 ex1)
"abababababababababab"

>>> runGen 44 (generate 10 20 ex1)
"ababab"

ex1run1 :: IO ()

Example 2

ex2 :: RE Void

>>> match ex2 "aaa"
True

Note: how "sharing" is preserved.

>>> showRef ex2
size: 5
show: App (Star (Ch "a")) (Star (Ch "a"))
null: True

> matchR ex2 "aaa"

True

>>> runGen 42 (generate 10 20 ex2)
"aaaaaa"

>>> runGen 44 (generate 10 20 ex2)
"aaaaaaaaaa"

ex2run1 :: IO ()

Example 3

ex3 :: RE Void

>>> match ex3 "abab"
True

>>> match ex3 "ababa"
False

>>> showRef ex3
size: 8
show: Ref 0 (Alt Eps (App (Ch "a") (App (Ch "b") (Ref 0 <<loop>>))))
null: True

>>> matchR ex3 "abab"
True

>>> matchR ex3 "ababa"
False

>>> runGen 43 (generate 10 20 ex3)
"abababab"

>>> runGen 44 (generate 10 20 ex3)
"abab"

ex3run1 :: IO ()

Example 4

ex4 :: RE Void

>>> match ex4 "aaaabbbb"
True

>>> showRef ex4
size: 8
show: Ref 0 (Alt Eps (App (Ch "a") (App (Ref 0 <<loop>>) (Ch "b"))))
null: True

>>> matchR ex4 "aaaabbbb"
True

>>> runGen 43 (generate 10 20 ex4)
"ab"

>>> runGen 47 (generate 10 20 ex4)
"aaaabbbb"

ex4run1 :: IO ()

Example 5

ex5 :: RE Void

>>> match ex5 "abab"
True

>>> match ex5 "ababa"
False

>>> showRef ex5
size: 8
show: Ref 0 (Alt Eps (App (Ref 0 <<loop>>) (App (Ch "a") (Ch "b"))))
null: True

>>> matchR ex5 "abab"
True

>>> matchR ex5 "ababa"
False

>>> runGen 43 (generate 10 20 ex5)
"ab"

>>> runGen 51 (generate 10 20 ex5)
"abab"

ex5run1 :: IO ()

Example 6

ex6 :: RE Void

Using fix-point operator:

fix expr = "(" expr ")" | "1" | "2" | ... | "9" | expr "+" expr | expr "*" expr

which in BNF is almost he same

expr ::= "(" expr ")" | "1" | "2" | ... | "9" | expr "+" expr | expr "*" expr

>>> matchR ex6 "(1+2)*3"
True

>>> runGen 43 (generate 5 5 ex6)
"74501+(534*19450)*(99050)"

ex6run1 :: IO ()

Example 7

exCfg :: Ord a => CFG Nat5 a

exCfgN :: Vec Nat5 Name

ex7 :: Ord a => RE a

>>> matchR ex7 "12"
True

>>> matchR ex7 "(1+2)*3"
True

>>> charClasses ex7
fromList "\NUL()*+,0:"

>>> runGen 43 (generate 5 5 ex7)
"(3431*((0337+5+070346+4))+76848+((4126+350875)*98769+308194+270+03118)+888*(95+90904)+(301069+7+715835)+2809)"

ex7run1 :: IO ()

ex7run :: String -> IO ()

ex7parsec :: Parser ()

ex7parsecRun :: IO ()

Example 8

Example 9