Is there a more succinct way to get one column of a dplyr tbl as a vector, from a tbl with database back-end (i.e. the data frame/table can’t be subset directly)? require(dplyr) db <- src_sqlite(tempfile(), create = TRUE) iris2 <- copy_to(db, iris) iris2$Species # NULL That would have been too easy, so collect(select(iris2, Species))[, 1] … Read more
I noticed that Scala provide lazy vals. But I don’t get what they do. scala> val x = 15 x: Int = 15 scala> lazy val y = 13 y: Int = <lazy> scala> x res0: Int = 15 scala> y res1: Int = 13 The REPL shows that y is a lazy val, but … Read more
I came across the following definition as I try to learn Haskell using a real project to drive it. I don’t understand what the exclamation mark in front of each argument means and my books didn’t seem to mention it. data MidiMessage = MidiMessage !Int !MidiMessage 3 Answers 3
I found this article about Lazy: Laziness in C# 4.0 – Lazy What is the best practice to have best performance using Lazy objects? Can someone point me to a practical use in a real application? In other words, when should I use it? 7 Answers 7
I am trying to read a large file one line at a time. I found a question on Quora that dealt with the subject but I’m missing some connections to make the whole thing fit together. var Lazy=require(“lazy”); new Lazy(process.stdin) .lines .forEach( function(line) { console.log(line.toString()); } ); process.stdin.resume(); The bit that I’d like to figure … Read more
