Disclaimer

The content of this blog is my personal opinion only. Although I am an employee - currently of Imagination Technologies's MIPS group, in the past of other companies such as Intellectual Ventures, Intel, AMD, Motorola, and Gould - I reveal this only so that the reader may account for any possible bias I may have towards my employer's products. The statements I make here in no way represent my employer's position, nor am I authorized to speak on behalf of my employer. In fact, this posting may not even represent my personal opinion, since occasionally I play devil's advocate.

See http://docs.google.com/View?id=dcxddbtr_23cg5thdfj for photo credits.

Tuesday, January 24, 2012

Code ordering, want none: perl example

I have several times posted how I find languages without code ordering pleasant, more readable.

E.g.
  let x = y + z
      where z = some log and complicated expressions
Here's an example from writing "shell scripts" - although here I am doing the shell script in Perl: Start off with:
   system("command with some long and complicated command line");
Realize that you want to repeat the command in a pre-announcement of what you are doing, and in an error message: Start off with:
   print "RUNNING: command with some long and complicated command line\n";
   my $exitcode = system("command with some long and complicated command line");
   print "error: exitcode=$exitcode: command with some long and complicated command line\n"
      if there_is_a_problem($exitcode);
Now avoid repetition: Standard way:
   my $cmd = command with some long and complicated command line";
   print "RUNNING: $cmd";
   my $exitcode = system("cmd");
   print "error: exitcode=$exitcode: $cmd\n"
      if there_is_a_problem($exitcode);
In my opinion the non-code ordered way is more readable:
{
   my $cmd;  # maybe some declaration to say it is not ordered?
   print "RUNNING: $cmd";
   my $exitcode = system($cmd = "command with some long and complicated command line");
   print "error: exitcode=$exitcode: $cmd\n"
      if there_is_a_problem($exitcode);
}
I think it is more readable because you see the value set at the point where it matters, where it is used most intensely (the other uses are mild, just prints). Note that I have used a scope.