Scan

Scan is like Reduce but returns all intermediate accumulator values. Also known as prefix scan or cumulative fold. Useful for tracking running totals, running maximums, or other cumulative operations.

package main

import (
 "fmt"
 u "github.com/rjNemo/underscore"
)

func main() {
 // Running sum
 nums := []int{1, 2, 3, 4}
 add := func(acc, n int) int { return acc + n }
 fmt.Println(u.Scan(nums, 0, add)) // [1, 3, 6, 10]

 // Running maximum
 values := []int{3, 1, 4, 1, 5, 9, 2}
 max := func(acc, n int) int {
  if n > acc {
   return n
  }
  return acc
 }
 fmt.Println(u.Scan(values, 0, max)) // [3, 3, 4, 4, 5, 9, 9]

 // String concatenation
 words := []string{"hello", "world", "!"}
 concat := func(acc, s string) string { return acc + s }
 fmt.Println(u.Scan(words, "", concat)) // ["hello", "helloworld", "helloworld!"]
}