1 files changed, 62 insertions, 0 deletions
diff --git a/subex/filter.go b/subex/filter.go
new file mode 100644
index 0000000..1a1b6db
--- /dev/null
+++ b/subex/filter.go
@@ -0,0 +1,62 @@
+package subex
+
+import (
+	"main/walk"
+)
+
+type valueFilter interface {
+	valueFilter(value walk.Value) bool
+}
+
+type selectScalarFilter struct {
+	scalar walk.Scalar
+}
+func (scalar selectScalarFilter) valueFilter(value walk.Value) bool {
+	return value == scalar.scalar
+}
+
+type anyNumberFilter struct {}
+func (_ anyNumberFilter) valueFilter(value walk.Value) bool {
+	_, isNumber := value.(walk.NumberScalar)
+	return isNumber
+}
+
+type anyBoolFilter struct {}
+func (_ anyBoolFilter) valueFilter(value walk.Value) bool {
+	_, isBool := value.(walk.BoolScalar)
+	return isBool
+}
+
+type anyValueFilter struct {}
+func (_ anyValueFilter) valueFilter(value walk.Value) bool {
+	return true
+}
+
+type anyArrayFilter struct {}
+func (_ anyArrayFilter) valueFilter(value walk.Value) bool {
+	_, isArray := value.(walk.ArrayStructure)
+	return isArray
+}
+
+type anyStringFilter struct {}
+func (_ anyStringFilter) valueFilter(value walk.Value) bool {
+	_, isString := value.(walk.StringStructure)
+	return isString
+}
+
+
+type runeFilter interface {
+	runeFilter(r walk.StringRuneAtom) bool
+}
+
+type anyRuneFilter struct {}
+func (_ anyRuneFilter) runeFilter(r walk.StringRuneAtom) bool {
+	return true
+}
+
+type selectRuneFilter struct {
+	r rune
+}
+func (f selectRuneFilter) runeFilter(r walk.StringRuneAtom) bool {
+	return f.r == rune(r)
+}