Re: How to isolate bits

Aussie Susan — Mon, 30 Jan 2012 22:50:44 GMT

Can you please let us know the regex variant you are using - they are not all the same and provide different capabilities and syntax extensions?

Also, am I right in assuming that by "bit" you are referring to the "0"s and "1" in the first part of your input line before the first "=" character (the part that looks like a binary sum)? If so, am I right in assuming that the bits are counted from the left (and not the right within each value as would normally be the case; from least significant to the most significant)? Perhaps an example of the values you would expect to have captured in the "var1" , var2" etc would help.

Having said all that, I'm not sure that you can do what you are asking (or what I think you are asking) for directly within the regex. The reason is that you cannot skip characters within a capture group and I think you are wanting the spaces and "+" characters to not be included.

Remember that a regex pattern works on characters and has absolutely no understanding of numbers or separators and similar classifications that we (people) may apply automatically.

You could use something like:

^(\d{4})\s+(\d)(\d)(\d{2})\D+(\d{4})\s+(\d{4})\D+(\d{3})(\d)\s+(\d{4})

and then use match group #1 to construct "var1", match group #2 to make "var2", and match group #3 for "var3". "var4" will need to be made from the concatenation of match groups #4, #5, #6, and #7, and "var5" will be the concatenation of match groups #8 and #9.

As I said, the pattern has to account for every character in the match, including the spaces and other non-digit characters. However, the above regex plus some string concatenation will give you the strings that you are after.

An alternative is to do a bit of string manipulation first to get rid of all non-digit characters (or even non-"0" and "1" characters) and the use a regex to process the resulting string of binary digits.

Of course, this all assumes that the actual layout of the string is always exactly as you have given in your single example.

If that is the case, then you may be better of using standard string operations: 1) replace all non-digits with a null and then 2) use the sub-string functions directly on the resulting string. This will probably be faster and have a smaller memory footprint (unless the regex library is being used elsewhere in the program).

Susan

How to isolate bits

zallz — Mon, 30 Jan 2012 16:37:55 GMT

I want to extract bits out of my regex string.

Here's what I want to do :

input string : 0001 0001 + 0010 0010 + 0011 0011 = 0x11 + 0x22 + 0x33 = "173451"

var1 is the first 4 bits;

var2 is the 5th bit;

var3 is the 6th bit;

var4 is the following 13 bits;

var5 is the last 5 bits.

Thank you

Construction Advice

Re: How to isolate bits

How to isolate bits