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IvanVergiliev / predicate_fold.scala
Created June 21, 2021 16:04
Fold a list of predicates
val andPredicates: Array[Column] = parseAndPredicates(...)
val compositePredicate: Column = andPredicates.foldLeft(lit(true))((x, y) => x && y)
@IvanVergiliev
IvanVergiliev / exponential_tree_transform
Created June 21, 2021 16:01
Exponential Tree Transformation Complexity
f(H) =
  f(H - 1) // for the first transform call
  +
  f(H - 1) // for the second transform call
= 2 * f(H - 1) =
= 2 * 2 * f(H - 2) = ... = 2 ^ (H - 1) * f(1) // unfolding further
@IvanVergiliev
IvanVergiliev / tree_fold.scala
Created June 17, 2021 20:39
Balanced fold
import org.apache.spark.sql.Column
def treeFold(
  columns: List[Column],
  initialValue: Column,
  op: (Column, Column) => Column
): Column = {
  if (columns.isEmpty) {
    initialValue
  } else if (columns.length == 1) {
@IvanVergiliev
IvanVergiliev / tree_transform_dry.scala
Created June 17, 2021 20:35
Tree Transformation Algorithm with Code Reuse
def transformTree(tree: Tree): Option[Tree] = {
// Notice that there's no `canTranform` - we're using
// `transform().isDefined` to check for transformability!
  val transformedLeft = if (transform(tree.left).isDefined) {
    transform(tree.left)
} else None
...
}
@IvanVergiliev
IvanVergiliev / transform.scala
Created June 17, 2021 20:34
Tree Transformation Algorithm
def transformTree(tree: Tree): Option[Tree] = {
  val transformedLeft = if (canTransform(tree.left)) {
    transform(tree.left)
} else None
  val transformedRight = if (canTransform(tree.right)) {
    transform(tree.right)
} else None
val result = if (transformedLeft.isDefined && transformedRight.isDefined) {
@IvanVergiliev
IvanVergiliev / to_string.cc
Last active March 16, 2017 22:30
#include <cstdlib>
#include <string>
// All of the below are not really standards-compliant, but good enough
// for experiments.
void* operator new(std::size_t size) {
printf("Calling new(%zu).\n", size);
return std::malloc(size);
}
@IvanVergiliev
IvanVergiliev / NonVolatileFlag.java
Last active May 16, 2016 18:02
package io.github.ivanvergiliev;
public class NonVolatileFlag {
private static boolean flag = false;
public static class FlagChecker implements Runnable {
public void run() {
long iter = 0;
while (flag == false) {
++iter;
@IvanVergiliev
IvanVergiliev / power.cc
Created July 12, 2015 12:57
Compile time Fibonacci
#include <cstdio>
#include <array>
using std::array;
const int MOD = 1000;
class ArrayWrapper {
const array<int, 2>& value;
@IvanVergiliev
IvanVergiliev / gist:bb62c1af502fdfa800fd
Created August 13, 2014 07:32
var HelloMessage = React.createClass({
render: function() {
return <script>function f() { var a = 5; }</script>;
}
});
@IvanVergiliev
IvanVergiliev / tuple.cpp
Last active August 23, 2023 14:10
C++ Tuple implementation
#include <cstdio>
template<typename First, typename... Rest>
struct Tuple: public Tuple<Rest...> {
Tuple(First first, Rest... rest): Tuple<Rest...>(rest...), first(first) {}
First first;
};
template<typename First>