Got a suggestion to create a cheat sheet showing how to convert math symbols and expressions into Ko...

# datascience

[thomasnield]

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

[orangy]

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

[elizarov]

Math.pow(x, 2.0) -> x.pow(2)

[elizarov]

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()

[elizarov]

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) }

[elizarov]

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

[thomasnield]

@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

[thomasnield]

Putting those improvements into the sheet.

[holgerbrandl]

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

[elizarov]

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

[thomasnield]

@elizarov that would be amazing