Dear Shlomi, Are you able to write a version that uses a function called "doors"?
Kind regards, Samuel On 4/05/2010, at 3:01 AM, Shlomi Fish wrote: > Hi John, > > On Monday 03 May 2010 17:42:16 John W. Krahn wrote: >> Samuel Williams wrote: >>> Dear Friends, >> >> Hello, >> >>> It would also be great if someone could rewrite the Perl source code >>> >>> example so that it is as close as possible to the C implementation: >>> http://programming.dojo.net.nz/languages/c/index >>> >>> /* Include the standard input / output functions */ >>> #include <stdio.h> >>> >>> int main() >>> { >>> >>> /* Initialize the array of doors to 0 (closed) */ >>> char is_open[100] = {0}; >> >> Why are you creating an array of 101 elements when you only use 100? >> Your comment says you initialize the array but you only initialize the >> first element. > > Actually, in C: > > 1. A << type_t myarray[100]; >> will initialise an array that can be indexed > from 0 to 99 - 100 elements in total. Likewish myarray[10] will be indexed > from 0 to 9, etc. > > 2. The {0} is a shortened initialisation to allocate all the elements as 0. > >> >>> int pass, door; >>> >>> /* Process the doors */ >>> for (pass = 0; pass < 100; ++pass) >>> >>> for (door = pass; door < 100; door += pass+1) >>> >>> is_open[door] = !is_open[door]; >>> >>> /* Print out the results */ >>> for (door = 0; door < 100; ++door) >>> >>> printf("Door #%d is %s.\n", door+1, (is_open[door] ? "open." : >>> "closed.")); >>> >>> return 0; >>> >>> } >> >> sub main() >> { > > 1. Why did you put everything in a main fuction? Perl is not C. > > 2. Why the "()" after the main? You shouldn't specify prototypes. > >> # Initialize the array of doors to 0 (closed) >> $is_open[100] = 0; > > 1. Why didn't you declare @is_open? You should have used strict and warnings. > > 2. This will initialise the element of index 100 (actually the 101st element) > to 0 and all the elements before it (assuming they did not exist beforehand) > to undef. You probably want << @is_open = ((0) x 100) >> instead. > >> >> # Process the doors >> for ($pass = 0; $pass < 100; ++$pass){ > > 1. PBP recommends against doing C-style for loops. > > 2. you should declare pass again. > > 3. You should have some space before the "{" (I start it on a newline and > have > my reasons for that but I accept the other style). > >> for ($door = $pass; $door < 100; $door += $pass+1){ >> $is_open[$door] = !$is_open[$door];}} > > Ahmmm.. why didn't you put the two "}" in separate lines? Perl is not Lisp. > >> >> # Print out the results >> for ($door = 0; $door < 100; ++$door){ >> printf("Door #%d is %s.\n", $door+1, ($is_open[$door] ? "open." >> >> : "closed."));} > > Just a note - the C program has a bug where the strings had a trailing "." > which was also included in the printf's formatting string. It should not be > reproduced in the Perl program. > > Regards, > > Shlomi Fish > >> >> return 0; >> } >> >> >> >> >> John > > -- > ----------------------------------------------------------------- > Shlomi Fish http://www.shlomifish.org/ > Rethinking CPAN - http://shlom.in/rethinking-cpan > > God considered inflicting XSLT as the tenth plague of Egypt, but then > decided against it because he thought it would be too evil. > > Please reply to list if it's a mailing list post - http://shlom.in/reply . > > -- > To unsubscribe, e-mail: beginners-unsubscr...@perl.org > For additional commands, e-mail: beginners-h...@perl.org > http://learn.perl.org/ > > -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
