Interpret string to form sequence of numbers

I want to see if something like this already has been discussed (so I am not reinventing the wheel). Basically, I will read in a string (from a GUI) that defines a sequence of numbers, where (as an example):

temp_str = '1,2,4-9,12-20(2)';

And then, after interpreting the contents of the string, the output to the code would yield a numeric array with values:

temp_seq = [1,2,4,5,6,7,8,9,12,14,16,18,20];

Has anyone come across a thread that discusses something similar to this? If so, let me know as I would like to clean up and make my version more efficient.

Answer 1

[David Young]

Could you ask the user to enter 4:9 instead of 4-9, and 12:2:20 instead of 12-20(2)? If so (and also if you can trust the user not to enter functions that might have side effects instead of numbers), there's a one-liner that will do it:

>> temp_str = '1,2,4:9,12:2:20';
>> temp_seq = str2num(temp_str);

temp_seq =

    Columns 1 through 8

       1     2     4     5     6     7     8     9

    Columns 9 through 13

      12    14    16    18    20

If you want to stick to your original hyphen-based input format, it's still pretty easy to use regexprep to switch it to the colon-operator format.

EDIT: regexprep code added

To do this translation, assuming all the input numbers are positive integers, you could use:

>> temp_str2 = regexprep(temp_str, {'-' ':(\d+)\((\d+)\)'}, {':', ':$2:$1'})

This all assumes that the user sticks to the rules when they type in the string. Robust GUI code should do error checking to enforce this, but you would then end up writing a mini-parser. Whether the short-cut using regexprep and str2num is satisfactory depends on how public and sensitive the application is.

[Dr. Seis]

I think that is a good idea. I would be more than happy to see how to switch the comma-dash-parenthetic-operator format to a colon-operator format.

Looks like this will turn about 40 lines of code into maybe 2 or 3.

[David Young]

OK, I'll put the regexp line in the question for better formatting.

[Dr. Seis]

This is most excellent. I am going to have to familiarize myself with this "regexp" stuff in order to increase efficiency with future code. Thanks, David!