lexer: IsNot(), IsIn(), IsOneOf()

Signed-off-by: Alejandro Mery <amery@jpi.io>

lexer/runes.go

@@ -1,6 +1,38 @@
 package lexer
 
-import "unicode"
+import (
+	"strings"
+	"unicode"
+)
+
+// IsNot generates a rune condition checker that reverses the
+// decision of the given checker.
+func IsNot(cond func(rune) bool) func(rune) bool {
+	return func(r rune) bool {
+		return !cond(r)
+	}
+}
+
+// IsIn generates a rune condition checker that accepts runes
+// contained on the provided string
+func IsIn(s string) func(rune) bool {
+	return func(r rune) bool {
+		return strings.ContainsRune(s, r)
+	}
+}
+
+// IsOneOf generates a run condition checker that accepts runes
+// accepted by any of the given checkers
+func IsOneOf(s ...func(rune) bool) func(rune) bool {
+	return func(r rune) bool {
+		for _, cond := range s {
+			if cond(r) {
+				return true
+			}
+		}
+		return false
+	}
+}
 
 // IsSpace reports whether the rune is a space character as
 // defined by Unicode's White Space property