Seeing is Believing gem
15 Feb 2015Just thought I’d share a cool little gem I came across recently. As mentioned in the README, it was inspired by Bret Victor’s thought-provoking talk Inventing on Principle .
The Principle:
Creators need an immediate connection to what they create.
Seeing is believing acts like a multi-line, editor-based REPL (Read Evaluate Print Loop). For ruby, think IRB.
With seeing-is-believing, you can see what you’re doing right in the editor. As an example, we can trace through a binary search function:
def binary_search(array, target)
low = 0 # => 0
high = array.length - 1 # => 6
while low <= high # => true, true, true
mid = (low + high) / 2 # => 3, 1, 2
if array[mid] == target # => false, false, true
return mid # => 2
elsif array[mid] < target # => false, true
low = mid + 1 # => 2
elsif array[mid] > target # => true
high = mid - 1 # => 2
end
end
nil
end
array = [*'a'..'g'] # => ["a", "b", "c", "d", "e", "f", "g"]
binary_search(array, 'c') # => 2Rather than switching over to irb, we can checkout enumerators in the text editor as well:
# Playing around with enumerables and splat operator in this case
[*1..10] # => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
.select(&:even?) # => [2, 4, 6, 8, 10]
.map { |i| i * 2 } # => [4, 8, 12, 16, 20]
.take(2) # => [4, 8]And here’s another example checking out object classes:
# Checking out class
[*1..10].class # => Array
(1..10).class # => RangeCan I #map a range?
(1..10).class.included_modules # => [Enumerable, JSON::Ext::Generator::GeneratorMethods::Object, Kernel]
# Range class includes Enumerable so yes we can
(1..10) # => 1..10
.map { |i| i - 5 } # => [-4, -3, -2, -1, 0, 1, 2, 3, 4, 5]Again, the immediate feedback is nice!