How to sum array of numbers in Ruby

Question

I have an array of integers   For example   array    123 321 12389    Is there any nice way to get the sum of them   I know  that   sum   0 array each    a  sum  a     would work

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Ruby 2 4    Rails - array sum i e   1  2  3  sum     gt  6  Ruby pre 2 4 - array inject     or array reduce       Note  The  sum method is a new addition to 2 4 for enumerable so you will now be able to use array sum in pure ruby  not just Rails

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Alternatively  just for comparison   if you have Rails installed  actually just ActiveSupport    require  activesupport  array sum

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Method 1        1  pry main  gt   1 2 3 4  sum       gt  10      2  pry main  gt     sum       gt  0      3  pry main  gt   1 2 3 5 nil  sum     TypeError  nil can t be coerced into Integer   Method 2        24  pry main  gt     inject          gt  nil     25  pry main  gt     inject 0           gt  0     4  pry main  gt   1 2 3 4 5  inject 0           gt  15     5  pry main  gt   1 2 3 4 nil  inject 0         TypeError  nil can t be coerced into Integer    from  pry  5 in       Method 3       6  pry main  gt   1 2 3  reduce          gt  6     9  pry main  gt     reduce          gt  nil     7  pry main  gt   1 2 nil  reduce        TypeError  nil can t be coerced into Integer    from  pry  7 in       Method 4         When Array contains an nil and empty values  by default if you use any above functions reduce  sum  inject everything will through the       TypeError  nil can t be coerced into Integer   You can overcome this by       16  pry main  gt  sum   0       gt  0     17  pry main  gt   1 2 3 4 nil      each  a  sum   a to i        gt   1  2  3  4  nil          18  pry main  gt  sum      gt  10   Method 6        eval  Evaluates the Ruby expression s  in string      26  pry main  gt  a    1 3 4 5      gt   1  3  4  5     27  pry main  gt  eval a join         gt  13    30  pry main  gt  a    1 3 4 5  nil      gt   1  3  4  5  nil     31  pry main  gt  eval a join       SyntaxError   eval  1  syntax error  unexpected end-of-input   1 3 4 5

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array reduce 0        While equivalent to array inject 0       the term reduce is entering a more common vernacular with the rise of MapReduce programming models   inject  reduce  fold  accumulate  and compress are all synonymous as a class of folding functions  I find consistency across your code base most important  but since various communities tend to prefer one word over another  it   s nonetheless useful to know the alternatives   To emphasize the map-reduce verbiage  here   s a version that is a little bit more forgiving on what ends up in that array   array map  amp  to i  reduce 0        Some additional relevant reading    http   ruby-doc org core-1 9 3 Enumerable html method-i-inject http   en wikipedia org wiki MapReduce http   en wikipedia org wiki Fold  higher-order function

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You can use  map and  sum like   array map    e  e   sum

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Also allows for  1 2  sum  x  x   2      6     http   madeofcode com posts 74-ruby-core-extension-array-sum class Array   def sum method   nil   amp block      if block given        raise ArgumentError   You cannot pass a block and a method   if method       inject 0     sum  i  sum   yield i        elsif method       inject 0     sum  i  sum   i send method        else       inject 0     sum  i  sum   i       end   end end

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Or try the Ruby 1 9 way   array inject 0        Note  the 0 base case is needed otherwise nil will be returned on empty arrays    gt     inject     nil  gt     inject 0      0

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For Ruby   2 4 0 you can use sum from Enumerables    1  2  3  4  sum   It is dangerous to mokeypatch base classes   If you like danger and using an older version of Ruby  you could add  sum to the Array class   class Array   def sum     inject 0     sum  x  sum   x     end end

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If you feel golfy  you can do  eval  123 321 12389        This will create a string  123 321 12389  and then use function eval to do the sum  This is only for golfing purpose  you should not use it in proper code

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You can also do it in easy way  def sum numbers    return 0 if numbers length  lt  1   result   0   numbers each    num  result    num     result end

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Just for the sake of diversity  you can also do this if your array is not an array of numbers  but rather an array of objects that have properties that are numbers  e g  amount    array inject 0   sum x  sum   x amount

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Try this   array inject 0   sum x  sum   x     See Ruby s Enumerable Documentation   note  the 0 base case is needed so that 0 will be returned on an empty array instead of nil

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Ruby 2 4 0 is released  and it has an Enumerable sum method  So you can do  array sum   Examples from the docs     1   gt  10  2   gt  20   sum   k  v  k   v       gt  50  1  10  sum                                  gt  55  1  10  sum   v  v   2                       gt  110

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New for Ruby 2 4 0  You can use the aptly named method Enumerable sum  It has a lot of advantages over inject     but there are some important notes to read at the end as well    Examples  Ranges   1  100  sum    gt  5050   Arrays   1  2  4  9  2  3  sum    gt  21   1 9  6 3  20 3  49 2  sum    gt  77 7   Important note  This method is not equivalent to  inject      For example    w a b c  inject        gt   abc   w a b c  sum    gt  TypeError  String can t be coerced into Integer   Also    1  1000000000  sum    gt  500000000500000000  execution time  less than 1s   1  1000000000  inject        gt  500000000500000000  execution time  upwards of a minute    See this answer for more information on why sum is like this

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ruby 1 8 7 way is the following   array inject 0   amp

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for array with nil values we can do compact and then inject the sum ex-  a    1 2 3 4 5 12 23 45 nil 23 nil  puts a compact inject

[ruby] How to sum array of numbers in Ruby?

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