I am looking for a regular expression parser. I found the Nick Gammon 0.1.0 version, but that is too limited for the problem I am working on (no '|' metasymbol, no *,?,+ quantifiers on parenthesized groups). Can anyone advise?

Thanks. Yes, I agree I can easily do without the ‘syntactic sugar’, and your approach will certainly work for me as well. But I was only wondering if a regex library existed with which I could implement my approach with a few lines of code.

Thank you, I will look into this!

A Regex library is pretty extreme overkill to parse such trivial syntax. It can be done with a FAR smaller footprint, in terms of lines of code, memory, and CPU cycles, without Regex.

I guess you're right. I just recently made my first steps into the Arduino world, coming from PCs with abundant memory and cycles.

[image] johnpool: wondering if a regex library existed with which I could implement my approach with a few lines of code. i'm curious how you can simplify this to just a few lines using regex? what would they be?

In C#, I would use one or more of the methods below. using System.Text.RegularExpressions; public static Regex regex = new Regex( "^(? [a-zA-Z]\\w*)\$\\s*(? [a-zA-Z]\\w*|\\d+(\\."+ "\\d+)?|false|true|(\"[^\"]*\")*)(\\s*\\,\\s* (? ([a-zA-"+ "Z]\\w*|\\d+(\\.\\d+)?|false|true|(\"[^\"]*\"))*))*\\s*\$$" ); // Split the InputText wherever the regex matches string[] results = regex.Split(InputText); // Capture the first Match, if any, in the InputText Match m = regex.Match(InputText); // Capture all Matches in the InputText MatchCollection ms = regex.Matches(InputText); // Test to see if there is a match in the InputText bool IsMatch = regex.IsMatch(InputText); // Get the names of all the named and numbered capture groups string[] GroupNames = regex.GetGroupNames(); // Get the numbers of all the named and numbered capture groups int[] GroupNumbers = regex.GetGroupNumbers();

[image] johnpool: I guess you're right. I just recently made my first steps into the Arduino world, coming from PCs with abundant memory and cycles. Maybe have a look at the examples in Robin's updated serial input basics tutorial; it has some examples for parsing (of simple strings).

[image] johnpool: I would use one or more of the methods below. No, how are you going to put the value 22 from the string "motor1 22" into the variable motor1

[image] johnpool: \s*\,\s* (? After the/each comma, at least one space is required? In that case \s+ would be -- well "better" may be too strong.... (I used regex101.com BTW) This seems like a basic lexer, as you would use to parse a programming language. Each token is one of word that starts with a letter includes true and false number with optional decimal place string with double-quotes -- no embedded double-quote allowed symbols you care about: ( , ) Should be able to find examples out there to adapt, or recall from memory.

Hello kenb4, The spaces in the regex are insignificant. A 'real' space would be indicated by '\ '. There is a regex option IgnorePatternWhitespace to set this. An embedded " is denoted by "" (e,g, "abc""def"). This is handled correctly by the part of the pattern: (\"[^\"]*\")+, which actually defines a concatenation of strings without embedded quotes. (notice that I changed the erroneous final * in the original pattern into a +). I also agree that the "true" and "false" are unnecessary since the first alternative will also recognize them. Regards, John

Regular expressions

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sterretje October 8, 2024, 7:42am 17

Maybe have a look at the examples in Robin's updated serial input basics tutorial; it has some examples for parsing (of simple strings).

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Regular expressions

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