Add filter.Minus, HasPrefix and types

filter/filter.go

@@ -0,0 +1,54 @@
+package filter
+
+import "strings"
+
+// Number combines the primitives generally considered numbers by JSON
+// and other high-level structure data representations.
+type Number interface {
+	int16 | int32 | int64 | float32 | float64
+}
+
+// Text combines byte slice and string.
+type Text interface {
+	[]byte | string
+}
+
+// P is for "principle" in this case. These are the types that have
+// representations in JSON and other high-level structured data
+// representations.
+type P interface {
+	Number
+	Text
+	bool
+}
+
+// HasPrefix filters the Text input set and returns only those elements
+// that have the give prefix.
+func HasPrefix[T Text](set []T, pre string) []T {
+	m := []T{}
+	for _, s := range set {
+		if strings.HasPrefix(string(s), pre) {
+			m = append(m, s)
+		}
+	}
+	return m
+}
+
+// Minus performs a set "minus" operation by returning a new set with
+// the elements of the second set removed from it.
+func Minus[T Text, M Text](set []T, min []M) []T {
+	m := []T{}
+	for _, i := range set {
+		var seen bool
+		for _, n := range min {
+			if string(n) == string(i) {
+				seen = true
+				break
+			}
+		}
+		if !seen {
+			m = append(m, i)
+		}
+	}
+	return m
+}

filter/filter_test.go

@@ -0,0 +1,25 @@
+package filter_test
+
+import (
+	"fmt"
+
+	"github.com/rwxrob/bonzai/filter"
+)
+
+func ExampleHasPrefix() {
+	set := []string{
+		"one", "two", "three", "four", "five", "six", "seven",
+	}
+	fmt.Println(filter.HasPrefix(set, "t"))
+	// Output:
+	// [two three]
+}
+
+func ExampleMinus() {
+	set := []string{
+		"one", "two", "three", "four", "five", "six", "seven",
+	}
+	fmt.Println(filter.Minus(set, []string{"two", "four", "six"}))
+	// Output:
+	// [one three five seven]
+}