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That programming book you never finished

Arik on June 22, 2018

Tell me if this sounds familiar: You walk into a bookstore, browse through some shelves and run into a programming book about a subject you alwa...

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BillCarver • Jun 23 '18

Based on the opening, I was looking for strategies on finishing books.

Saviobosco • Jun 23 '18

Me too

itsjoel29 • Jun 23 '18

I was expecting the same U_u

Paula Hasstenteufel • Jun 28 '18

Yes.

Stelios Sfakianakis • Jun 23 '18

Personally I would think the following is the exact translation in Python of the math formula shown in the article:

  sum(2*i for i in range(1, 101))

(well... if you ignore the fact that the upper limit of range in not inclusive so I need to put 101 instead of 100)

So now that you know about Sigmas etc. you can read The Art of Computer Programming ;-)

Brandon Arnold • Jun 24 '18 • Edited

Try reducing computation by finding a closed form instead of writing a loop. Here, the closed form is f(n) = n*(n+1) (e.g. f(100) = 100*101 = 10100):

f(n) = S[1..n] 2*i     definition
     = 2 * S[1..n] i   pull out the coefficient
     = 2 * n*(n+1)/2   by triangular number formula
     = n*(n+1)         cancel the twos

Joaquim • Jun 23 '18

Not the topic I expected, bit was a nice read anyway.

Beni Cherniavsky-Paskin • Jun 26 '18

github.com/Jam3/math-as-code is a "cheatsheet" explaining tons of math notation by showing equivalent JavaScript code, similar to how this article explained Σ.