Tag: Map, filter & reduce
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Thinking with “map”
In the free Webinar I gave yesterday about functional programming, I mentioned that “map,” or its equivalent (e.g., Python’s list comprehensions), is a powerful tool that I use nearly every day. Once you get into the functional mode of thinking, you’re constantly finding ways to turn one collection into another collection. It’s a mindset that…
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Summary of my “reduce” series
I teach Ruby and Python to a lot of people — in formal courses, and in one-on-one pairing sessions, both online and in person. I’ve found that for many people, the whole notion of functional programming seems strange and difficult, as well as something of a waste of time. After all, if you have objects,…
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Implementing “filter” with “reduce”, in Ruby and Python
We’re nearly at the end of my tour of the “reduce” function in Ruby and Python. Just as I showed in the previous installment how we can implement the “map” function using “reduce”, I want to show how we can implement another functional-programming standard, “filter”, using “reduce” as well. As before, I’ll show examples in…
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Implementing “map” with “reduce”, in Ruby and Python
This is another installment in my “reduce” series of posts, aimed at helping programmers understand this function, with examples in both Ruby and Python. So far, we have seen how we can build a number of different types of data structures — integers, strings, arrays, and hashes — using “reduce”. But the really interesting use…
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Creating Ruby hashes with “reduce”
In yesterday’s post, I showed how we can use Python’s “reduce” function to create a dictionary. Ruby, of course, also has dictionaries, but calls them “hashes.” In this posting, I’m going to show how we can create a hash in Ruby when iterating over an enumerable. In so doing, we’ll see how we can use…
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Creating Python dictionaries with “reduce”
In the last few installments (first, second, third, and fourth) of this series, we saw how “reduce” can be used to build up a scalar value (such as a number or string), or even a simple collection, such as a list (in Python) or an array (in Ruby). The jewel in the data-structure crown for…
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Creating collections with “reduce”
In the first few parts of this series (first, second, and third), I introduced the “reduce” function, and showed how it can be used in a number of ways. However, in all of the examples we have seen so far, the output from our invocations of “reduce” were integers or strings. If we reduce with…
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Implementing “min” and “max” with “reduce”
This is the third installment of my “reduce” series of blog posts. For the first, see here, and for the second, see here. If you have been reading this series, then you know that “reduce” can be used to sum numbers, or to calculate scores. In that sense, “reduce” justifies its name; we’re invoking a…
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Calculating Scrabble scores with “reduce”
This is the second installment of my series of blog posts on the “reduce” function/method. For an introduction, see here. I love to play Scrabble — or more commonly nowadays, I play Words with Friends on my phone. (I often say that the game should instead be called, “Words with people who used to be your…
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Understanding “reduce” (first in a series)
One of the notable things about MIT’s computer science curriculum, at least back when I was studying there, was that you didn’t learn any “practical” programming languages. Our work was all done in either Scheme (a dialect of Lisp) or in CLU (an early object-oriented language). I can’t say that I have too many memories,…