Why can't I use "or" here?
in [Ruby]
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From: Phillip Gawlowski on 31 Dec 2009 01:43 On 31.12.2009 06:32, Albert Schlef wrote: > It works. But, I must say, it isn't as beautiful as my original plan. It > doesn't read as English. PS C:\Scripts> ruby .\unless.rb /unless.rb:1: Argument error (RuntimeError) PS C:\Scripts> ruby .\unless.rb "arg" PS C:\Scripts> cat .\unless.rb raise "Argument error" unless ARGV[0] PS C:\Scripts> I prefer it that way. :) Works in 1.8.6 and 1.9.1, too, to my great relief. -- Phillip Gawlowski
From: Jeff Peng on 31 Dec 2009 02:13 botp : > On Thu, Dec 31, 2009 at 10:24 AM, Albert Schlef <albertschlef(a)gmail.com> wrote: >> Why? I thought the only diference between "or" and "||" is the >> precedence. > > yes, so you can do eg > >>> system "pwd" or raise "no command here" > /home/botp > => true > >>> system "asdf" or raise "no command here" > RuntimeError: no command here > > if you know perl, this is no surprise.. > I know Perl, but I'm still surprised. # perl -le 'print undef or 4' # perl -le 'print(undef or 4)' 4 # irb irb(main):001:0> puts nil or 4 => 4 irb(main):002:0> puts(nil or 4) SyntaxError: (irb):2: syntax error, unexpected keyword_or, expecting ')' puts(nil or 4) ^ from /usr/bin/irb:12:in `<main>' And if I "puts (nil or 4)" (there is a blank between them) will print 4. (Just my thought,I was thinking this is a bug.) Regards, Jeff.
From: Seebs on 31 Dec 2009 03:22 On 2009-12-31, Albert Schlef <albertschlef(a)gmail.com> wrote: > Interesting. > > Why is the following a syntax error? > > puts (123 if true) > > and the following isn't? > > puts (123 or 456) The if modifier has to go on the tail end of the containing complete expression. You could say "statement", but I don't think that really adds anything. But that's not the same issue as why "or" doesn't work in a method argument without extra (). -s -- Copyright 2009, all wrongs reversed. Peter Seebach / usenet-nospam(a)seebs.net http://www.seebs.net/log/ <-- lawsuits, religion, and funny pictures http://en.wikipedia.org/wiki/Fair_Game_(Scientology) <-- get educated!
From: Albert Schlef on 31 Dec 2009 04:31 Seebs wrote: > On 2009-12-31, Albert Schlef <albertschlef(a)gmail.com> wrote: >> Interesting. >> >> Why is the following a syntax error? >> >> puts (123 if true) >> >> and the following isn't? >> >> puts (123 or 456) > > The if modifier has to go on the tail end of the containing complete > expression. Then why does the following work? a = (123 if true) -- Posted via http://www.ruby-forum.com/.
From: Phillip Gawlowski on 31 Dec 2009 04:35
On 31.12.2009 10:31, Albert Schlef wrote: > Then why does the following work? > > a = (123 if true) Because here you do an assignment. Ruby Appliance's Beginner VM will need a list of Ruby gotchas. :S -- Phillip Gawlowski |