|Perl: the Markov chain saw|
Are global variables "bad"?by jpearl (Scribe)
|on Apr 21, 2009 at 16:13 UTC||Need Help??|
jpearl has asked for the
wisdom of the Perl Monks concerning the following question:
I'm writing a ptk application to visualize some genomic data we are working with. I read in a file and store a variety of information in a HoA about strains of bacteria etc. However, the file is rather large and it takes a minute or so to parse, so I would like to only do that once.
Currently the HoA and a couple other data (i.e. # of strains, array of strain names) are stored as (references to) global variables. I have a getter and setter function which currently is the only one that directly interacts with the variables. I always have a queasy sort of feeling when using globals, a lurking suspicion in my mind that eventually this will come back and bite me in some mysterious and underhanded way.
Several functions in the program use this data, and so I do want "global" access. None of the functions change the actual original HoA et. al. once the intial file read is done. So, my question boils down to: is it a bad idea to have global variables? If it is how can I encapsulate them in perl so I can pass handles around to the functions that need the data? Or is having getter and setter functions "safe" enough?
Update:Just wanted to say "thank you" for all the great comments and links for further study. PMs is definitely in a league of its own for considerate first-rate responses.