added some hashes programs

hash_creation_1_a.rb

@@ -0,0 +1,7 @@
+#!/usr/bin/ruby
+# hash_creation_1_a.rb
+marks = { :English => 50, :Math => 70, :Science => 75 }
+puts "Key => Value"
+marks.each { |a,b|
+	puts "#{a} => #{b}"
+}

hash_creation_2.rb

@@ -1,7 +1,7 @@
 #!/usr/bin/ruby
 # hash_creation_2.rb
-# this does not work, hence must omitted from book
-marks = { 'English': 50, 'Math': 70, 'Science': 75 }
+
+marks = { English: 50, Math: 70, Science: 75 }
 puts "Key => Value"
 marks.each { |a,b|
 	puts "#{a} => #{b}"

x/2n100.rb

@@ -0,0 +1,9 @@
+n = 1
+
+while (2**n) <= (100*n*n)
+	# n += 0.01
+	n = n + 0.1
+	puts n
+end
+
+puts n

x/additive_combinations.rb

@@ -0,0 +1,37 @@
+class Array
+	def sum
+		total = 0
+		for element in self
+			total += element
+		end
+		total
+	end
+
+	def increment base = 1
+		array = self.collect {|x| x }
+		array_length = array.length
+		i = 0
+		loop do
+			unless array[i]
+				array << 0
+				return array
+			end
+
+			if array[i] % base == 0 and array[i] !=0
+				array[i] = 0
+				i = i+1
+			else
+				array[i] = array[i]+1
+				return array
+			end
+		end
+	end
+end
+
+number = 5 # just change this to get various combinations
+a = [0]
+loop do
+	puts a.join ' + ' if a.sum == number
+	break if a.length > number
+	a = a.increment number
+end

x/diamond.rb

@@ -0,0 +1,18 @@
+# printa a diamond of desired height
+
+height = 7 # height should be minimu 3 and must be a odd number
+h = height - 2
+width = 2*h-3
+j=1
+
+(h-1).downto(0) { |i|
+	puts " "*(i) + "#"*j
+	j=j+2
+}
+
+(1).upto(h-1) { |i|
+	puts " "*i + "#" * width
+	width=width-2
+
+}
+

x/factorials.rb

@@ -0,0 +1 @@
+re

x/fixnum_prime.rb

@@ -0,0 +1,12 @@
+class Fixnum
+	def prime?
+		b = 0
+		a = self
+		return true if a <= 2
+		2.upto(a){ |n|
+			b = n
+			break if a%n == 0
+		}
+		b == a
+	end
+end

x/goldbatch.rb

@@ -0,0 +1,17 @@
+require './fixnum_prime.rb'
+
+# display every odd number from 4 to 100 as sum of two different prime
+# numbers 
+
+prime_array = [] #empty array
+1.upto(100){ |x| prime_array << x if x.prime? } # gets all pime from 1 to 100 into prime_array
+
+4.step(100,2){ |num|
+	for prime in prime_array
+		diff = num - prime
+		if prime_array.index diff
+			puts "#{num} = #{prime} + #{diff}" 
+			break # comment break to have all possible combinations
+		end
+	end
+}

x/prime_from_1_to_100.rb

@@ -0,0 +1,4 @@
+require './fixnum_prime.rb'
+
+1.upto(100){ |x| puts x if x.prime? }
+

x/pyramid 2.rb

@@ -0,0 +1,3 @@
+# program prints a pyramid
+height = 15
+height.times{ |j| 	puts " "*(height-(1+j)) + "#"*(2*j+1) }

x/pyramid.rb

@@ -0,0 +1,9 @@
+# program prints a pyramid
+height = 15
+space = height -1
+i = 0
+height.times{
+	puts " "*space + "#"*(2*i+1)
+	space = space -1
+	i = i+1
+}