Did you know you can do this with Ruby out of the box?
# A real lambda
λ { puts ‘Hello’ }.call => ‘Hello’
# Sigma - sum of all elements
∑(1,2,3) => 6
# Square root
√ 49 => 7.0
How difficult was this to implement? Keep reading!
# Be sure to run with the "-Ku" flag!
module Kernel
alias λ proc
def ∑(*args)
sum = 0
args.each{ |e| sum += e }
sum
end
def √(root)
Math.sqrt(root)
end
end
Pretty tricky, eh?
Just remember the “-Ku”. :)
Cool! Works equally well inside Array, to do things such as [ 1, 2, 3 ].∑
Cool stuff :)
You could even make this shorter by changing the Sum method to args.inject(0){|sum,i| sum += i }
Flurin Egger: Why +=? There's no point in assigning to sum since it's the block's return value that is kept.
Yay; pretty-lambdas (http://www.emacswiki.org/cgi-bin/wiki/PrettyLambda) is no longer necessary for ruby-mode. Now how do you type that again?
@Flurin - I could have used inject, except I hate that method.
@Phil - I used MS Windows character map and did a copy/paste.
You should love Array#inject. And also, you should have ∑ 1,2,3, not ∑ [1,2,3] because of your asterisk.
why should he love it
i myself hate several things and feel better not
using them, in the end whats important is loving to
use RUBY, not some method or specific way :)
@Daniel - whoops, yeah, fixed. Well, I could also flatten all arguments, but ok.
That's great! I was honestly just thinking about this for replacing #lambda 10 minutes ago, but I wouldn't have known about the -Ku flag.
Very cool trick.
When you want to use this feature, but are not able to guarantee the command line switch, you may as well execute
$KCODE = "u"
before using Unicode characters in method names.
@schmidt - I tried setting that at the top of the code, but it doesn't work. I get parse errors. I'll have to ask on the list as to why.
Hah! Excellent.
Just the hacky kind of thing this blog needs.
I like it :D.
@Daniel Berger
You probably tried something like this:
[code]
$KCODE = "u"
def ∑
#...
end
[/code]
It doesn't work of course. But try this:
[code]
#file: run.rb
$KCODE = "u"
require 'fun_with_utf'
[/code]
[code]
#file: fun_with_utf.rb
def ∑
#...
end
puts ∑(...)
[/code]
and run with command: ruby run.rb (without -Ku). It should work.
Explanation is very simple. In first example ruby try to parse source code, but see strange characters and raise errors. In second example ruby parses file "run.rb" and everything is ok. Next it executes file, variable's value $KCODE is changed to "u" so now it can handle utf. Next it load external file "fun_with_utf.rb", so ruby parses it. But now it can do it, because it can recognize characters like "∑".
See difference?
Now we need an engineering keyboard with a row of common greek letters used in math.
@radarak - Thanks, figured it was something like that.
@mccoyn - I've actually thought about that. Is there any sort of standard layout that's been discussed? I wonder if the Unicode Consortium has any thoughts.
mccoyn: Yes! Then we'll be able to go back to APL!
This is brilliant!
> This is brilliant!
i think similar) very cool)
and open for other opportunities a plenty full bunch of ideas. Thanks for the UTF (32bit and higher :-)
so amazing! it gives me a new view of unicode.
Great post,
would never have thought it would be that easy