Re : Re: Re : Re: match pattern anomaly?

[dan_u]

I agree the icon is incorrect. But I'd still say the behaviour is correct. The first instance of an empty string is at the very beginning of each string. b* matches an empty string so the first instance is at position 0. If you need at least one instance use b+ as reg. exp. instead.

[tbob]

In all other languages and operating systems, * matches any number of any characters.  Like in a cmd line, b* will match anything beginning with b (ba, bbbbb, bqwerty).  Why must Labview be different?  With an input string of abbc, and a pattern of b*, using the * convention of almost all other languages, the outputs would be: before=a, match=bbc, after=<blank>.  But nooooo, Labview has to define it differently so as to confuse everyone and make them learn two interpretations of *.  Same with question mark.  Pattern b? should return before=a, match=bb, after=c.  Without having to read the help files, this is what I would expect.  I wish this was the way it was.  But its too late now, everyone is used to the unique Labview definitions.

[shoneill]

"In all other languages and operating systems, * matches any number of any characters.  Like in a cmd line, b* will match anything beginning with b (ba, bbbbb, bqwerty).  Why must Labview be different?"

Is this so bad?  The function is returning what the help says it should.  And ALL other languages? You sure?  I know it's a typical wildcard, but is it true that ALL other languages use this as a "anything" wildcard?  This would seem to suggest otherwise for C at least......

Shane.

[tbob]

No it isn't so bad.  In fact, once you are used to the syntax, it isn't bad at all.  Maybe * isn't a wildcard for EVERY other language, but it is pretty common amongst windows users.  My question is why didn't the Labview developers stick with the commonality?  It would have made life just a little easier.

[Matt_W1]

They did stick with commonality, LV implements match pattern using regular expression syntax. Match pattern is a probably a DFA and match regular expression a NFA (if your curious on why there's two functions). Regular expressions are more common than * and ? in programming languages (perl, ruby,  tcl, labview, c++ with boost, .Net, PHP, Haskell etc). I've personally have only used * and ? on the command line and never in a programing language. Also the * and ? form is less expressive.

The icon not matching the function is messed up though.

[Matt_W1]

I just remembered the * and ? form is called a glob

[parthabe]

Just came here for reeading.

Nice knowledge base.

[parthabe]

Can somebody explain more of wildcard search ?

I cannot understand fully.

[dan_u]

@tbob: stick to windows conventions? It's much less powerful than the options offered by match pattern. Look at the alternates for example. There are limited special characters available (like *,?,+,...) and once you're familiar with the match pattern regular expression syntax it's really powerful. I wouldn't want to be limited to the windows wildcards * (any number of any character) or ? (any character).

btw, if you place the "Match Regular Expression" function on the block diagram it has nearly the same icon as match pattern, but with b+ instead of b*...