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How to Read Numeric Symbols Only within Specific Sequence of a String using Lexical Class Type

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I had a look at some archive posts regarding reading specific characters in a string. 


One that I was really enticed by was Altenbach's example using Lexical Class Type: Re: Removing non-alpha-numeric characters from a string




I have attached the VI so you can have a look. 


The only drawback at the moment is that I only want to identify the first sequence of numbers and then stop. For example, I have a string which reads: An-54


Currently the VI indicator will be 54 because the for loop goes through the entire string. I actually only want 5 to be read because a special character follows. I am not interested in any numeric (code 3) afterwards. 


Here are a few more examples to clarify what I want to achieve: 


Input: AC1505  

Desired Output: 150 


Input: AI>00005

Desired Output: 0000 


The desired outcome is for the match to occur with only the first sequence of number/s (from left to right) and stop matching once a different code (other than 3) is read. 


Would anyone have any ideas on how to achieve that? 


Many Thanks

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Message 1 of 5
Accepted by topic author neunited

Is there any particular reason for using the Lexical Class node here? It's a pretty straightforward regex. If you really want to do it with lexical class, you can make your loop conditional and use a boolean shift register to keep track of whether matching has started.

Message 2 of 5

Lexical Class is a better option performance wise in comparison to the "search and replace all" which is a multipurpose VI. For parsing and matching the lexical class seemed to be a more viable option to use. 

However the issue now is that I actually want to include all minus signs and decimal places, for example:


Input: BK-0.03:

Desired Output : -0.03


One possibility could be by adding further conditions in the case structure or with the use of enums. 


Let me know if you have any better suggestions. 


Many Thanks

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Message 3 of 5

I managed to solve my own query. 


VI attached for your reference. If you have any other alternatives feel free to share them Smiley Happy

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Message 4 of 5

I have my doubts that your lexical processing is more efficient than the regex and the regex is certainly more compact.

In almost all cases, I would expect the performance difference to be negligible. If it is important to you, I'd be curious to see how the benchmarks show out.


I think your approach could be further simplified to use a conditional tunnel on the output. You've also created an artificial stop condition in this case where you had to know that your last digit/term character was 3.

Lexical Digit Grab.png

Your approach is the top one. My regex is the bottom.

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