Message from JavaScript discussions

August 2017

— Https://


Hmmm! Might be making a RegExp diff algorithm that diffs them based on what they can understand rather than direct string comparison... this is a little quick deterministic finite automata implementation I wrote for fun, but will likely have some use in the diff algorithm

— The bottom is a DFA that can understand HELLO

— RegExp: /hello/

is equivalent to DFA:


— So it then becomes a graph diff problem! :D

— Not sure what you mean?

— You can convert a regular expression to a deterministic finite automata

— Then traverse that automata tree and derive strings... you can traverse infinite amounts at the same time and find out if they all derive the same strings

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— Nice.

— They are 1:1 mapping as a DFA and regex can describe each other 100%

— So if you have <w{5}> how can you tell it derives the same string as /hello/ without passing in any data or otherwise running the regular expression builtins? You do simple comparison operators on the transition ranges between the nodes, very simple!

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— All ranges for the first one would be {0, 65535} whereas for the second one it would vary... {72, 72} and then {69, 69} etc... since the ranges of the second expression fit into the ranges of the first you can say "Yes, these two expressions can derive the same string". If you want a strict result that says "these two expressions derive the same EXACT strings, no more and no less", then you can do a direct strict equality comparison instead

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