I made a benchmark program for purescript-parsing which benchmarks against this purescript-string-parsers package.

https://github.com/purescript-contrib/purescript-parsing/blob/main/bench/Main.purs

Here are the results of benchmarking many anyDigit

Text.Parsing.StringParser.CodePoints

StringParser.runParser parse23Points
mean   = 746.70 ms
stddev = 12.21 ms
min    = 738.42 ms
max    = 794.27 ms

Text.Parsing.StringParser.CodeUnits

StringParser.runParser parse23Units
mean   = 10.10 ms
stddev = 1.13 ms
min    = 9.46 ms
max    = 24.07 ms

Text.Parsing.Parser.String

runParser parse23
mean   = 44.20 ms
stddev = 6.38 ms
min    = 42.25 ms
max    = 113.16 ms

Data.String.Regex

Regex.match pattern23
mean   = 728.23 μs
stddev = 339.32 μs
min    = 613.72 μs
max    = 2.97 ms

There is something terribly wrong with Text.Parsing.StringParser.CodePoints.anyDigit and I think I know what. The problem is that codePointAt is linear, so many anyDigit then becomes quadratic.

(EDIT deleted notes about stuff not related to this issue)