Let's TDD clojure.core/reduce
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Summary: clojure.core/reduce is a powerful function, yet the code for
it is so simple. It's four lines! We TDD our own implementation.
A couple of weeks ago I introduced a TDD-in-the-browser
system and applied it to build map. reduce
is another cornerstone of functional programming. I explained how
reduce works recently, so that should
help understand it from the outside.
But how does it work from the inside? Let's write a version of reduce.
Specification
Define a function my-reduce. It should take three arguments. The first
argument, f, is a function. The second argument is the initial value.
And the third argument is a collection of values. f is a function of
two arguments. my-reduce should take one value from the collection and
apply f to the initial argument and the first value. The return value
of f will become the new initial value, and then
COMMING SOON
Conclusion
clojure.core/reduce is a very useful function. It's one of those
functions I wish I had started using earlier. And building a version of
reduce yourself can help you understand how the recursion works.
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