Ethiopian multiplication: Difference between revisions
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(→{{header|LOLCODE}}: Named functions is from the 1.3 proposal, not 1.2 spec) |
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Iterative and recursive implementations here. |
Iterative and recursive implementations here. |
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I've chosen to highlight the example 20*5 which I think is more illustrative. |
I've chosen to highlight the example 20*5 which I think is more illustrative. |
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<lang ruby>def |
<lang ruby>def halve(x) x/2 end |
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def |
def double(x) x*2 end |
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def double(x); x*2; end |
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# iterative |
# iterative |
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def |
def ethiopian_multiply(a, b) |
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product = 0 |
product = 0 |
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while a >= 1 |
while a >= 1 |
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p [a, b, |
p [a, b, a.even? ? "STRIKE" : "KEEP"] if $DEBUG |
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product += b |
product += b unless a.even? |
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a = halve(a) |
a = halve(a) |
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b = double(b) |
b = double(b) |
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# recursive |
# recursive |
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def |
def rec_ethiopian_multiply(a, b) |
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return 0 if a < 1 |
return 0 if a < 1 |
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p [a, b, |
p [a, b, a.even? ? "STRIKE" : "KEEP"] if $DEBUG |
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(a.even? ? 0 : b) + rec_ethiopian_multiply(halve(a), double(b)) |
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end |
end |
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$DEBUG = true # $DEBUG also set to true if "-d" option given |
$DEBUG = true # $DEBUG also set to true if "-d" option given |
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a, b = 20, 5 |
a, b = 20, 5 |
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puts "#{a} * #{b} = #{ |
puts "#{a} * #{b} = #{ethiopian_multiply(a,b)}"; puts</lang> |
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{{out}} |
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Output: |
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<pre> |
<pre> |
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[20, 5, "STRIKE"] |
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[10, 10, "STRIKE"] |
[10, 10, "STRIKE"] |
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[5, 20, "KEEP"] |
[5, 20, "KEEP"] |
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def test_rec6; assert_equal(0, rec_ethopian_multiply(0,5)); end |
def test_rec6; assert_equal(0, rec_ethopian_multiply(0,5)); end |
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end</lang> |
end</lang> |
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<pre> |
<pre>Run options: |
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Started |
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# Running tests: |
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............ |
............ |
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Finished in 0. |
Finished tests in 0.014001s, 857.0816 tests/s, 857.0816 assertions/s. |
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| ⚫ | |||
ruby -v: ruby 2.0.0p247 (2013-06-27) [i386-mingw32] |
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| ⚫ | |||
</pre> |
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=={{header|Scala}}== |
=={{header|Scala}}== |
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