Got a suggestion to create a cheat sheet showing how to conv kotlinlang #datascience

Got a suggestion to create a cheat sheet showing how to convert math symbols and expressions into Kotlin code. Here's the start, contributions welcome. https://github.com/thomasnield/kotlin_math_cheatsheet/blob/master/README.md

👍 10

❤️ 1

orangy

09/21/2018, 10:26 AM

https://github.com/Jam3/math-as-code

✔️ 1

elizarov

09/21/2018, 12:13 PM

Math.pow(x, 2.0)

x.pow(2)

👍 2

Nested sums look much closer to math using builder notation:

(1..4).flatMap { i -> (4..20).map { j -> 2 * i * j } }.sum()

sequence { for(i in 1..4) for (j in 4..20) yield(2 * i * j) }.sum()

Btw, somewhere around 1.4 (when we have new type inference) we can offer an even better (and much faster) version of “sum builder” in stdlib:

sum { for(i in 1..4) for (j in 4..20) add(2 * i * j) }

https://youtrack.jetbrains.com/issue/KT-27028

thomasnield

09/21/2018, 2:06 PM

@elizarov Cool, it looks similar to Python comprehensions without the weird backwardness. This would be awesome to have as well as improving range and progressions for continuous numeric types. https://github.com/Kotlin/KEEP/pull/137

Putting those improvements into the sheet.

holgerbrandl

09/26/2018, 3:18 PM

@elizarov Are there some docs/teaser already about how type inference is going to change in 1.4?

elizarov

09/26/2018, 8:26 PM

Nothing is definite yet. We hope that inference is going to smart enough, so that we can overload by return type of lambda….

thomasnield

09/26/2018, 10:08 PM

@elizarov that would be amazing

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