Class: FundingPrimer::MultiplicationTable

Inherits:
Object
  • Object
show all
Defined in:
lib/funding_primer/multiplication_table.rb

Overview

FundingPrimer::MultiplicationTable is a 2-dimensional multiplication table of an enumerator of numbers.

It can be thought of as the Cartesian product of a vector with itself, plus some optional headings

Instance Method Summary collapse

Constructor Details

#initialize(numbers) ⇒ MultiplicationTable

Returns a new instance of MultiplicationTable.



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# File 'lib/funding_primer/multiplication_table.rb', line 7

def initialize(numbers)
  @numbers = numbers.to_a
end

Instance Method Details

#raw_array ⇒ Object

produces and caches a raw 2D array of pair-wise products from @numbers

Example:

FundingPrimer::MultiplicationTable.new(1..3).raw_array
# => [[1,2,3],
#     [2,4,6],
#     [3,6,9]]



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# File 'lib/funding_primer/multiplication_table.rb', line 19

def raw_array
  @raw_array ||= @numbers.product(@numbers).map {|pair| pair.inject :*}.each_slice(@numbers.length).to_a
end

#with_headings ⇒ Object

produces an array with row and column headings

Example:

FundingPrimer::MultiplicationTable.new(1..3).with_headings
# => [[nil,1,2,3],
#     [1,  1,2,3],
#     [2,  2,4,6],
      [3,  3,6,9]]



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# File 'lib/funding_primer/multiplication_table.rb', line 32

def with_headings
 column_headings = [nil].concat @numbers 
 array_with_row_headings = @numbers.zip(raw_array).map &:flatten
 array_with_row_headings.unshift column_headings
end