1 files changed, 8 insertions, 3 deletions
diff --git a/main/command.go b/main/command.go
index ba6f9dc..ea6fb59 100644
--- a/main/command.go
+++ b/main/command.go
@@ -107,6 +107,7 @@ func (cmd DeleteAllCommand) exec(state *ProgramState) {
 
 type SubstituteCommand struct {
 	subex subex.SubexState
+	next Command
 }
 func (cmd SubstituteCommand) exec(state *ProgramState) {
 	valueStream := make(chan walk.WalkValue)
@@ -119,15 +120,19 @@ func (cmd SubstituteCommand) exec(state *ProgramState) {
 	atomStream := walk.Atomise(valueStream)
 	atomsOut, error := subex.RunTransducer(cmd.subex, atomStream)
 	if error {
-		panic("Error running subex")
+		return
 	}
 	valuesOut, err := walk.MemoryCompound(atomsOut)
 	if err != nil {
-		panic("Error compounding atoms")
+		return
 	}
 	state.value = valuesOut
+	cmd.next.exec(state)
 }
 
 type Command interface {
 	exec(*ProgramState)
-}
-\ No newline at end of file
+}
+
+type NoopCommand struct {}
+func (cmd NoopCommand) exec(state *ProgramState) {}
+\ No newline at end of file