A handful of methods that could be added to the class
They are not perfect, but I use them quite a lot.
Some of them (or similar methods) will be present in Ruby 1.9. For example there will be a method
As you see, they are better than my
Ruby 1.9 is also going to have
Move to Enumerable
One more enhancement that can be done in the above code is to move all the methods in the module
Add to load path
If you create some files that you'd like to be easily accessible in your Ruby programs, you can add the path to your files to Ruby load path, so that you will be able to
RUBYLIB = P:/ath/To/Your/Dir
The path will be automatically added to Ruby load path each time Ruby starts, which can be verified by typing
If you want some of your files to be loaded even without the need to
-rubygems -rstart
Each word starting with -r makes ruby load a file named by the rest of the word. Ruby will find your file because you already added file path to Ruby load path. If you want to load more files at startup, it is best to
As you might have guessed, there is file named ubygems that the original content of the variable caused to load. The strange name is in fact chosen only to make the whole command sound reasonable. All it does is load rubygems.rb, which initialises the Gems engine, enabling programs to use additional libraries.
Array:class Array
def sum
s=0
each{|e| s+=e}
s
end
def mul
m=1
each{|e| m*=e}
m
end
def mean
sum.to_f/length
end
def map_with_index
i=-1
map{|e| yield(e,i+=1)}
end
def map_with_index!
i=-1
map!{|e| yield(e,i+=1)}
end
def any_with_index?
each_with_index{|e,i| return true if yield(e,i)}
false
end
def all_with_index?
each_with_index{|e,i| return false unless yield(e,i)}
true
end
def find_index
each_with_index{|v,i| return i if yield(v)}
end
def find_indices
ret=[]
each_with_index{|v,i| ret<<i if yield(v)}
ret
end
def select_by_index(*indices)
ret=[]
indices.each{|ind| ret<<self[ind]}
ret
end
alias find_indexes find_indices
def to_hash
raise "Cannot convert to Hash!" unless all?\
{ |e|
e.respond_to? :length and e.length==2 and e.respond_to? :[]
}
h={}
each{|e| h[e[0]]=e[1]}
h
end
def keys_to_hash
h={}
each{|e| h[e]=yield(e)}
h
end
def keys_with_index_to_hash
h={}
each_with_index{|e,i| h[e]=yield(e,i)}
h
end
def with(a2)
ensure_same_length(a2)
map_with_index{|e,i| [e,a2[i]]}
end
def with_to_hash(a2)
ensure_same_length(a2)
h={}
each_with_index{|e,i| h[e]=a2[i]}
h
end
def count_all
h={}
each\
{ |e|
h[e]||=0
h[e]+=1
}
h
end
def group_by
h={}
each\
{ |e|
g=yield(e)
h[g]||=[]
h[g]<< e
}
h.map{|g,ee| ee}
end
alias contain? include?
alias has? include?
def rand
a=to_a
a[Kernel.rand(a.length)] unless a.empty?
end
private
def ensure_same_length(arg)
raise ArgumentError,"Argument must be of the same length!"\
unless arg.respond_to? :length and length==arg.length\
and arg.respond_to? :[]
end
end
Some of them (or similar methods) will be present in Ruby 1.9. For example there will be a method
inject (or reduce) working like this:[1,4,5].reduce(:*) #=> 20 # 1*4*5
["a","b","dd"].reduce(:+) #=> "abdd"
sum, because they work for any type for which the operation is defined. This reduce is not hard to implement, too, but it will probably work a bit faster when included in Ruby core.Ruby 1.9 is also going to have
group_by, working exactly like mine, as far as I know.Move to Enumerable
One more enhancement that can be done in the above code is to move all the methods in the module
Enumerable (just write module Enumerableinstead of
class Arrayat the top). It allows you to use these methods also with other enumerable types, like
Hash. You'll have to test the methods, though, as not all of them make sense when used with structures where the elements are not ordered.Add to load path
If you create some files that you'd like to be easily accessible in your Ruby programs, you can add the path to your files to Ruby load path, so that you will be able to
require your files without giving the full path. Under Windows, just go to environment variables, and addRUBYLIB = P:/ath/To/Your/Dir
The path will be automatically added to Ruby load path each time Ruby starts, which can be verified by typing
$: (or $LOAD_PATH) in irb and looking for your path.If you want some of your files to be loaded even without the need to
require them, then you can add them to the environment variable RUBYOPT. This variable can already contain -rubygems. If you want the file P:/ath/To/Your/Dir/start.rb to be loaded at startup, change the variable to-rubygems -rstart
Each word starting with -r makes ruby load a file named by the rest of the word. Ruby will find your file because you already added file path to Ruby load path. If you want to load more files at startup, it is best to
require them from within your first file.As you might have guessed, there is file named ubygems that the original content of the variable caused to load. The strange name is in fact chosen only to make the whole command sound reasonable. All it does is load rubygems.rb, which initialises the Gems engine, enabling programs to use additional libraries.
