doc: add documentation

Dockerfile

@@ -7,5 +7,4 @@ RUN go mod download
 
 COPY *.go ./
 
-#RUN go test -json ./... -count=1 -cover | gotestfmt
-RUN go test ./...
+RUN go test ./... -cover

Makefile

@@ -1,5 +1,2 @@
-lint:
-	golangci-lint run --fix
-
 test:
-	go test -json ./... -count=1 -cover | gotestfmt
+	docker build .

each.go

@@ -1,7 +1,8 @@
 package underscore
 
-func Each[T any](values []T, predicate func(T)) {
+// Each iterates over a slice of elements, yielding each in turn to an action function.
+func Each[T any](values []T, action func(T)) {
 	for _, v := range values {
-		predicate(v)
+		action(v)
 	}
 }

filter.go

@@ -1,5 +1,6 @@
 package underscore
 
+// Filter looks through each value in the slice, returning a slice of all the values that pass a truth test (predicate).
 func Filter[T any](values []T, predicate func(T) bool) (res []T) {
 	for _, v := range values {
 		if predicate(v) {

map.go

@@ -1,9 +1,11 @@
 package underscore
 
-func Map[T, P any](values []T, predicate func(T) P) []P {
+// Map produces a new slice of values by mapping each value in the slice through
+// a transform function.
+func Map[T, P any](values []T, transform func(T) P) []P {
 	res := make([]P, 0, len(values))
 	for _, v := range values {
-		res = append(res, predicate(v))
+		res = append(res, transform(v))
 	}
 	return res
 }

reduce.go

@@ -1,8 +1,10 @@
 package underscore
 
-func Reduce[T, P any](values []T, predicate func(T, P) P, acc P) P {
+// Reduce combine a list of values into a single value.
+// acc is the initial state, and each successive step of it should be returned by the reduction function.
+func Reduce[T, P any](values []T, reduction func(T, P) P, acc P) P {
 	for _, v := range values {
-		acc = predicate(v, acc)
+		acc = reduction(v, acc)
 	}
 	return acc
 }