update

utils/slice/slice.go

@@ -0,0 +1,184 @@
+package slice
+
+import (
+	"bufio"
+	"bytes"
+	"cmp"
+	"io"
+	"iter"
+	"slices"
+
+	"golang.org/x/exp/maps"
+)
+
+func Map[T any, R any](t []T, mapFunc func(T) R) []R {
+	r := make([]R, len(t))
+	for i, e := range t {
+		r[i] = mapFunc(e)
+	}
+	return r
+}
+
+func MapWithArg[I any, O any, A any](t []I, arg A, mapFunc func(A, I) O) []O {
+	return Map(t, func(e I) O {
+		return mapFunc(arg, e)
+	})
+}
+
+func Group[T any, K comparable](s []T, keyFunc func(T) K) map[K][]T {
+	m := map[K][]T{}
+	for _, item := range s {
+		k := keyFunc(item)
+		m[k] = append(m[k], item)
+	}
+	return m
+}
+
+func ToMap[T any, K comparable, V any](s []T, transformFunc func(T) (K, V)) map[K]V {
+	m := make(map[K]V, len(s))
+	for _, item := range s {
+		k, v := transformFunc(item)
+		m[k] = v
+	}
+	return m
+}
+
+func CompactByFrequency[T comparable](list []T) []T {
+	counters := make(map[T]int)
+	for _, item := range list {
+		counters[item]++
+	}
+
+	sorted := maps.Keys(counters)
+	slices.SortFunc(sorted, func(i, j T) int {
+		return cmp.Compare(counters[j], counters[i])
+	})
+	return sorted
+}
+
+func MostFrequent[T comparable](list []T) T {
+	var zero T
+	if len(list) == 0 {
+		return zero
+	}
+
+	counters := make(map[T]int)
+	var topItem T
+	var topCount int
+
+	for _, value := range list {
+		if value == zero {
+			continue
+		}
+		counters[value]++
+		if counters[value] > topCount {
+			topItem = value
+			topCount = counters[value]
+		}
+	}
+
+	return topItem
+}
+
+func Insert[T any](slice []T, value T, index int) []T {
+	return append(slice[:index], append([]T{value}, slice[index:]...)...)
+}
+
+func Remove[T any](slice []T, index int) []T {
+	return append(slice[:index], slice[index+1:]...)
+}
+
+func Move[T any](slice []T, srcIndex int, dstIndex int) []T {
+	value := slice[srcIndex]
+	return Insert(Remove(slice, srcIndex), value, dstIndex)
+}
+
+func Unique[T comparable](list []T) []T {
+	seen := make(map[T]struct{})
+	var result []T
+	for _, item := range list {
+		if _, ok := seen[item]; !ok {
+			seen[item] = struct{}{}
+			result = append(result, item)
+		}
+	}
+	return result
+}
+
+// LinesFrom returns a Seq that reads lines from the given reader
+func LinesFrom(reader io.Reader) iter.Seq[string] {
+	return func(yield func(string) bool) {
+		scanner := bufio.NewScanner(reader)
+		scanner.Split(scanLines)
+		for scanner.Scan() {
+			if !yield(scanner.Text()) {
+				return
+			}
+		}
+	}
+}
+
+// From https://stackoverflow.com/a/41433698
+func scanLines(data []byte, atEOF bool) (advance int, token []byte, err error) {
+	if atEOF && len(data) == 0 {
+		return 0, nil, nil
+	}
+	if i := bytes.IndexAny(data, "\r\n"); i >= 0 {
+		if data[i] == '\n' {
+			// We have a line terminated by single newline.
+			return i + 1, data[0:i], nil
+		}
+		advance = i + 1
+		if len(data) > i+1 && data[i+1] == '\n' {
+			advance += 1
+		}
+		return advance, data[0:i], nil
+	}
+	// If we're at EOF, we have a final, non-terminated line. Return it.
+	if atEOF {
+		return len(data), data, nil
+	}
+	// Request more data.
+	return 0, nil, nil
+}
+
+// CollectChunks collects chunks of n elements from the input sequence and return a Seq of chunks
+func CollectChunks[T any](it iter.Seq[T], n int) iter.Seq[[]T] {
+	return func(yield func([]T) bool) {
+		s := make([]T, 0, n)
+		for x := range it {
+			s = append(s, x)
+			if len(s) >= n {
+				if !yield(s) {
+					return
+				}
+				s = make([]T, 0, n)
+			}
+		}
+		if len(s) > 0 {
+			yield(s)
+		}
+	}
+}
+
+// SeqFunc returns a Seq that iterates over the slice with the given mapping function
+func SeqFunc[I, O any](s []I, f func(I) O) iter.Seq[O] {
+	return func(yield func(O) bool) {
+		for _, x := range s {
+			if !yield(f(x)) {
+				return
+			}
+		}
+	}
+}
+
+// Filter returns a new slice containing only the elements of s for which filterFunc returns true
+func Filter[T any](s []T, filterFunc func(T) bool) []T {
+	var result []T
+	for _, item := range s {
+		if filterFunc(item) {
+			result = append(result, item)
+		}
+	}
+	return result
+}