Moved to https://parsing.stereobooster.com/
- blog post http://matt.might.net/articles/parsing-with-derivatives/
- video https://www.youtube.com/watch?v=ZzsK8Am6dKU
- paper http://matt.might.net/papers/might2011derivatives.pdf
- implementation http://www.ucombinator.org/projects/parsing/
- another implementation https://github.com/webyrd/relational-parsing-with-derivatives
| Name | Regular expression | Chomskian grammar | PCRE | Language |
|---|---|---|---|---|
| empty language | ∅ |
{} |
||
| trivial language | ϵ |
S → ε | ^$¹ or ^.{0}$¹ |
{ε} |
| singleton lang. | a |
S → a | ^a$ |
{a} |
| concatenation | ab or a∘b |
S → ab | ^ab$ |
{ab} or {a}∘{b} |
| union | a+b or a⋃b |
S → a | b | ^[ab]$ or ^(a|b)$ |
{a,b} or {a}⋃{b} |
| Kleene star² | a* or a★ |
S → ε | aS | ^a*$ or ^a{0,}$ |
{ε,a,aa, ...} |
| Kleene plus | aa* or a∘a★ |
S → a | aS | ^a+$ or ^a{1,}$ |
{a,aa, ...} |
a+ϵ or a⋃ϵ |
S → a | ε | ^a?$ or ^a{0,1}$ |
{a,ε} or {a}⋃{ε} |
|
| alphabet | S → a | b | ... | ^.$¹ |
{a,b,c,d, ...} or Σ |
|
| difference | S → b | c | ... | ^[^a]$¹ |
{b,c,d,e, ...} or Σ - {a} |
¹ - approximation ² - repetition
PCRE - Perl Compatible Regular Expressions
* 0 or more quantifier
+ 1 or more quantifier; also "possessive quantifier"
? 0 or 1 quantifier; also quantifier minimizer
^ assert start of string (or line, in multiline mode)
$ assert end of string (or line, in multiline mode)
. match any character except newline (by default)
[ start character class definition
| start of alternative branch
^ negate the class, but only if the first character
] terminates the character class
TODO:
- better tree representation
- implement all compaction rules
Idea: use new node of type "recursive" instead of letrec function