Adds the NOT operator

1 files changed, 24 insertions, 0 deletions

diff --git a/subex/arithmetic.go b/subex/arithmetic.go
index 4404a1c..52f576d 100644
--- a/subex/arithmetic.go
+++ b/subex/arithmetic.go
@@ -152,3 +152,27 @@ func reciprocalValues(atoms []walk.Atom) ([]walk.Atom, error) {
 	}
 	return reciprocals, nil
 }
+
+// If all are castable to booleans, NOTs all and returns them
+// Else errors
+func notValues(atoms []walk.Atom) (notted []walk.Atom, err error) {
+	values, err := walk.MemoryCompound(atoms)
+	if err != nil {
+		return nil, err
+	}
+	for _, value := range values {
+		switch v := value.(type) {
+			case walk.ValueNull:
+				notted = append(notted, walk.ValueBool(true))
+			case walk.ValueBool:
+				notted = append(notted, walk.ValueBool(!v))
+			case walk.ValueNumber:
+				notted = append(notted, walk.ValueBool(v == 0))
+			case walk.ValueString:
+				notted = append(notted, walk.ValueBool(len(v) == 0))
+			default:
+				return nil, errors.New("Tried to NOT non-boolean")
+		}
+	}
+	return notted, nil
+}