> true || false;; val it : bool = true > true && false;; val it : bool = falseBut, these are syntax sugar. && and || are not only operators but also functions!
> (||) true false;; val it : bool = true > (&&) true false;; val it : bool = falseI have never known the fact until reading "Programming F# 3.0, 2nd Edition".
> let Mary'sCookie = "Yummy";; val Mary'sCookie : string = "Yummy"
gem 'rails', '3.2.9'
gem 'rake', '~> 0.9'
For help type #help;; > open Microsoft.FSharp.Data.UnitSystems.SI.UnitSymbols;; > let a = 195<m>;; val a : int<m> = 195 > [<Measure>] type km;; [<Measure>] type km > let b = 42<km>;; val b : int<km> = 42 > a + b;; a + b;; ----^ stdin(5,5): error FS0001: The unit of measure 'km' does not match the unit of measure 'm'In this case, we must create some functions to convert these.
For help type #help;; > open Microsoft.FSharp.Data.UnitSystems.SI.UnitSymbols;; > let a = 10<m>;; val a : int<m> = 10 > [<Measure>] type mile;; [<Measure>] type mile > let b = 9<mile>;; val b : int<mile> = 9 > a + b;; a + b;; ----^ stdin(5,5): error FS0001: The unit of measure 'mile' does not match the unit of measure 'm'In this case too, we must create some functions to convert these.
For help type #help;;
> open Microsoft.FSharp.Data.UnitSystems.SI.UnitSymbols;;
> seq {1<g>..10<g>};;
seq {1<g>..10<g>};;
-----^^^^^
stdin(7,6): error FS0001: The type 'int<g>' does not match the type 'int'In this case, we must do the redundant operation like below:> seq { for i in [1..10] -> i * 1<g> };;
val it : seq<int<g>> = seq [1; 2; 3; 4; ...]
require 'singleton'
# Fibonacci as Singleton class
class Fibonacci < Enumerator
include Singleton
def initialize
super { |y|
a = 0
b = 1
loop do
y << a
a, b = b, a + b
end
}
end
end
# define a refinement
module Nth
refine Enumerator do
def nth(n)
self.take(n+1).find.with_index { |elem, i| i == n }
end
end
end
begin
# there are no additional methods
puts Fibonacci.instance.lazy.nth(100)
rescue => e
puts e
end
#using refinments
using Nth
begin
# there is an additional method
puts Fibonacci.instance.lazy.nth(100)
rescue => e
puts e
end
$ cd /c/ruby-2.0.0 $ ./bin/ruby ~/fibonacci.rb undefined method `nth' for #<Enumerator::Lazy:0x26430d8> 354224848179261915075
Microsoft (R) F# Interactive version 11.0.50727.1 Copyright (c) Microsoft Corporation. All Rights Reserved. For help type #help;; > let fibonacci = Seq.cache <| Seq.unfold (fun (current, next) -> Some(current, (next, current + next))) (0I, 1I);; val fibonacci : seq> fibonacci |> Seq.nth 100;; val it : System.Numerics.BigInteger = 354224848179261915075 {IsEven = false; IsOne = false; IsPowerOfTwo = false; IsZero = false; Sign = 1;}
irb(main):001:0> RUBY_VERSION
=> "2.0.0"
irb(main):002:0> fibonacci = Enumerator.new { |y|
irb(main):003:1* a = 0
irb(main):004:1* b = 1
irb(main):005:1> loop do
irb(main):006:2* y << a
irb(main):007:2> a, b = b, a + b
irb(main):008:2> end
irb(main):009:1> }.lazy
=> #<Enumerator::Lazy: #<Enumerator: #<Enumerator::Generator:0x23cbbc0>:each>>
irb(main):010:0> def fibonacci.nth(n)
irb(main):011:1> self.take(n+1).find.with_index { |elem, i| i == n }
irb(main):012:1> end
=> nil
irb(main):013:0> fibonacci.nth(100)
=> 354224848179261915075
