```Issue #13209 has been reported by Jabari Zakiya.

----------------------------------------
Misc #13209: fact.rb in ruby/sample variations
https://bugs.ruby-lang.org/issues/13209

* Author: Jabari Zakiya
* Status: Open
* Priority: Normal
* Assignee:
----------------------------------------
I was looking at some of the Sample files that come with Ruby and
saw the example for doing factorials. It's an old example that I
thought I could make simpler/faster. Below are the results.

Maybe upgrading to show the difference between coding idioms can
be instructive to newer Ruby programmers.

```
def fact(n)
return 1 if n == 0
f = 1
n.downto(1) do |i|
f *= i
end
return f
end

def fact1(n)
return 1 if n | 1 == 1  # if n 0 or 1
f = 2
n.downto(3) do |i|
f *= i
end
return f
end

def fact2(n)
return 1 if n | 1 == 1  # if n 0 or 1
(2..n).reduce(:*)
end

require 'benchmark/ips'

Benchmark.ips do |x|
x.report("original factorial") { fact  100 }
x.report("modified factorial") { fact1 100 }
x.report("enhanced factorial") { fact2 100 }
x.compare!
end

```

Timings using ruby-2.4.0 on Linux 64-bit, on I7 cpu system.

```
Warming up --------------------------------------
original factorial     4.501k i/100ms
modified factorial     4.594k i/100ms
enhanced factorial     5.271k i/100ms
Calculating -------------------------------------
original factorial     44.962k (¡Þ 4.2%) i/s -    225.050k in   5.015176s
modified factorial     46.288k (¡Þ 3.2%) i/s -    234.294k in   5.066948s
enhanced factorial     53.425k (¡Þ 3.1%) i/s -    268.821k in   5.036635s

Comparison:
enhanced factorial:    53424.9 i/s
modified factorial:    46288.0 i/s - 1.15x  slower
original factorial:    44961.5 i/s - 1.19x  slower

=> true
2.4.0 :002 >

```

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