Think in Math, Write in Code

Post by jcora » Sat, Jul 20, 2019, 2:45 PM UTC

dr0wsy wrote: post #248

naturlich wrote: post #215

Earlier quoted context omitted.

That was the second part of my answer: a graph on paper. Draw nodes of execution and represent the branch as two arrows coming from the node and heading to new nodes. Label the arrows with the predicates of the branch. This is both definitely useful and definitely math.

> That was the second part of my answer: a graph on paper. Draw nodes of execution and represent the branch as two arrows coming from the node and heading to new nodes. Label the arrows with the predicates of the branch. Thanks! You don't happen to have some learning resources for modelling programs as state machines? I can't find anything when I search.

Post by justinmeiners » Sat, Jul 20, 2019, 11:00 PM UTC

dr0wsy wrote: post #249

justinmeiners wrote: post #230

Earlier quoted context omitted.

This is a great question. What I really tried to emphasize in the article is that math is not a formal language. Since its just you and coworkers, write out the parts you need as you need them, and ignore details. After all, its an exercise to help you think. If I needed uppercase I would just say: `up(s)` is a function that maps a string s to its uppercase string Writing that down, you and I already have a pretty go…

Thanks for the explanation! An example to check if I understood you correctly. `func1(r, s)` is a function that sends a request `r` to a given server `s`. It returns a status code from the server. How does that sound? It feels more like a spec than "doing math". > I highly recommend that book I linked in the article: "Introduction to Graph Theory" By: Trudeau I'll check it out! Does the book cover all the relevant pa…

Post by kragen » Wed, Jul 24, 2019, 4:58 PM UTC

kragen wrote: post #247

grovehaw wrote: post #47

Earlier quoted context omitted.

Some people feel at home with APL (A Programming Language) or its descendants. It was first developed by Ken Iverson as a notation to be used on paper for communicating procedures and algorithms. It was the subject of a book published in 1962, then became a programming language running on IBM mainframes in 1966. The following line of code produces all the prime numbers below the value R. (~T∊T∘.×T)/T←1↓⍳R More histor…

A fairly precise raw Python translation for the interested: T = range(1, R)[1:] # T←1↓ιR u = [[t*u for u in T] for t in T] # T∘.×T v = [t for ei, t in zip([any(t in ui for ui in u) for t in T], T) if not ei] # (~T∈u)/T As the standard poem on the subject by Dave Touretzky and Don Libes says: I wrote some hacks in APL, each on a single line. They're mutually recursive, and run in n-squared time! In this case, of cours…