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Programming-Idioms

  • Java
  • Clojure

Idiom #202 Sum of squares

Calculate the sum of squares s of data, an array of floating point values.

(defn square [x] (* x x))

(def s (transduce (map square) + data))

This doesn't create any intermediate collection
(defn square [x] (* x x))

(def s (reduce + (map square data)))
(defn square [x] (* x x))

(def s (->> data (map square) (reduce +)))
import static java.util.stream.DoubleStream.of;
import java.math.BigDecimal;
BigDecimal s = of(data)
    .mapToObj(String::valueOf)
    .map(BigDecimal::new)
    .map(x -> x.multiply(x))
    .reduce(BigDecimal::add)
    .get();
import static java.util.stream.DoubleStream.of;
double s = of(data).map(x -> x * x).sum();
import java.util.Arrays;
double s = Arrays.stream(data).map(i -> i * i).sum();

data has type double[]
using System.Linq;
var s = data.Sum(x => x * x);
New implementation...
< > ⌨
Bart 
(defn square [x] (* x x))

(def s (transduce (map square) + data))
(defn square [x] (* x x))

(def s (reduce + (map square data)))
(defn square [x] (* x x))

(def s (->> data (map square) (reduce +)))
BigDecimal s = of(data)
    .mapToObj(String::valueOf)
    .map(BigDecimal::new)
    .map(x -> x.multiply(x))
    .reduce(BigDecimal::add)
    .get();
double s = of(data).map(x -> x * x).sum();
double s = Arrays.stream(data).map(i -> i * i).sum();
var s = data.Sum(x => x * x);
var s = data.map((v) => v * v).reduce((sum, v) => sum + v);
s = sum( data**2 )
var s float64
for _, d := range data {
	s += math.Pow(d, 2)
}
def s = data.sum { it ** 2 }
sumOfSquares = sum . map (^2)
s = data.reduce((a, c) => a + c ** 2, 0)
var
  data: array of double;
...
  s := SumOfSquares(data);
...
my $s = sum map { $_ ** 2 } @data;
s = sum(i**2 for i in data)
f = lambda x: x * x
s = sum(map(f, data))
s = data.sum{ _1**2 }
s = data.sum{|i| i**2}
let s = data.iter().map(|x| x.powi(2)).sum::<f32>();