3 files changed, 114 insertions, 56 deletions

diff --git a/main/command.go b/main/command.go
index 296ad69..44fd9eb 100644
--- a/main/command.go
+++ b/main/command.go
@@ -3,10 +3,12 @@ package main
 import (
 	"main/walk"
 	"main/subex"
+	"fmt"
 )
 
 type Command interface {
 	exec(*ProgramState)
+	String() string
 }
 
 type PrintValueCommand struct {}
@@ -17,15 +19,10 @@ func (cmd PrintValueCommand) exec(state *ProgramState) {
 	}
 	path := walk.PathFromWalkValues(pathValues)
 	state.out.Print(path, state.value)
+	state.pc++
 }
-
-type SequenceCommand struct {
-	commands []Command
-}
-func (cmd SequenceCommand) exec(state *ProgramState) {
-	for _, command := range cmd.commands {
-		command.exec(state)
-	}
+func (cmd PrintValueCommand) String() string {
+	return "p"
 }
 
 type NextCommand struct {}
@@ -36,6 +33,10 @@ func (cmd NextCommand) exec(state *ProgramState) {
 	}
 	state.value = nextItem.Value
 	state.path = nextItem.Path
+	state.pc++
+}
+func (cmd NextCommand) String() string {
+	return "n"
 }
 
 type AppendNextCommand struct {}
@@ -46,16 +47,28 @@ func (cmd AppendNextCommand) exec(state *ProgramState) {
 	}
 	state.value = walk.ConcatData(state.value, nextItem.Value)
 	state.path = nextItem.Path
+	state.pc++
+}
+func (cmd AppendNextCommand) String() string {
+	return "N"
 }
 
 type DeleteValueCommand struct {}
 func (cmd DeleteValueCommand) exec(state *ProgramState) {
 	state.value = nil
+	state.pc++
+}
+func (cmd DeleteValueCommand) String() string {
+	return "d"
 }
 
 type DeletePathCommand struct {}
 func (cmd DeletePathCommand) exec(state *ProgramState) {
 	state.path = nil
+	state.pc++
+}
+func (cmd DeletePathCommand) String() string {
+	return "D"
 }
 
 func runSubex(state subex.Transducer, in []walk.Atom) (out []walk.Atom, error bool) {
@@ -68,43 +81,62 @@ func runSubex(state subex.Transducer, in []walk.Atom) (out []walk.Atom, error bo
 
 type SubstituteValueCommand struct {
 	subex subex.Transducer
-	next Command
 }
 func (cmd SubstituteValueCommand) exec(state *ProgramState) {
 	newValue, err := runSubex(cmd.subex, state.value)
 	if err {
-		return
+		state.pc++
+	} else {
+		state.pc += 2
+		state.value = newValue
 	}
-	state.value = newValue
-	cmd.next.exec(state)
+}
+func (cmd SubstituteValueCommand) String() string {
+	return "s/.../"
 }
 
 type SubstitutePathCommand struct {
 	subex subex.Transducer
-	next Command
 }
 func (cmd SubstitutePathCommand) exec(state *ProgramState) {
 	newPath, err := runSubex(cmd.subex, state.path)
 	if err {
-		return
+		state.pc++
+	} else {
+		state.pc += 2
+		state.path = newPath
 	}
-	state.path = newPath
-	cmd.next.exec(state)
+}
+func (cmd SubstitutePathCommand) String() string {
+	return "S/.../"
 }
 
 type NoopCommand struct {}
-func (cmd NoopCommand) exec(state *ProgramState) {}
+func (cmd NoopCommand) exec(state *ProgramState) {
+	state.pc++
+}
+func (cmd NoopCommand) String() string {
+	return "o"
+}
 
 type SwapXRegCommand struct {}
 func (cmd SwapXRegCommand) exec(state *ProgramState) {
 	v := state.value
 	state.value = state.xreg
 	state.xreg = v
+	state.pc++
+}
+func (cmd SwapXRegCommand) String() string {
+	return "x"
 }
 
 type AppendXRegCommand struct {}
 func (cmd AppendXRegCommand) exec(state *ProgramState) {
 	state.xreg = append(state.xreg, state.value...)
+	state.pc++
+}
+func (cmd AppendXRegCommand) String() string {
+	return "X"
 }
 
 type SwapYRegCommand struct {}
@@ -112,11 +144,19 @@ func (cmd SwapYRegCommand) exec(state *ProgramState) {
 	v := state.value
 	state.value = state.yreg
 	state.yreg = v
+	state.pc++
+}
+func (cmd SwapYRegCommand) String() string {
+	return "y"
 }
 
 type AppendYRegCommand struct {}
 func (cmd AppendYRegCommand) exec(state *ProgramState) {
 	state.yreg = append(state.yreg, state.value...)
+	state.pc++
+}
+func (cmd AppendYRegCommand) String() string {
+	return "Y"
 }
 
 type SwapZRegCommand struct {}
@@ -124,11 +164,19 @@ func (cmd SwapZRegCommand) exec(state *ProgramState) {
 	v := state.value
 	state.value = state.zreg
 	state.zreg = v
+	state.pc++
+}
+func (cmd SwapZRegCommand) String() string {
+	return "z"
 }
 
 type AppendZRegCommand struct {}
 func (cmd AppendZRegCommand) exec(state *ProgramState) {
 	state.zreg = append(state.zreg, state.value...)
+	state.pc++
+}
+func (cmd AppendZRegCommand) String() string {
+	return "Z"
 }
 
 type SwapPathCommand struct {}
@@ -136,9 +184,27 @@ func (cmd SwapPathCommand) exec(state *ProgramState) {
 	v := state.value
 	state.value = state.path
 	state.path = v
+	state.pc++
+}
+func (cmd SwapPathCommand) String() string {
+	return "k"
 }
 
 type AppendPathCommand struct {}
 func (cmd AppendPathCommand) exec(state *ProgramState) {
 	state.path = walk.ConcatData(state.path, state.value)
+	state.pc++
+}
+func (cmd AppendPathCommand) String() string {
+	return "K"
+}
+
+type JumpCommand struct {
+	destination int
+}
+func (cmd JumpCommand) exec(state *ProgramState) {
+	state.pc = cmd.destination
+}
+func (cmd JumpCommand) String() string {
+	return fmt.Sprintf("b%v", cmd.destination)
 }
\ No newline at end of file
diff --git a/main/main.go b/main/main.go
index 2067920..55ed5b5 100644
--- a/main/main.go
+++ b/main/main.go
@@ -13,6 +13,7 @@ type ProgramState struct {
 	in walk.JSONIn
 	out walk.JSONOut
 	program []Command
+	pc int
 }
 
 func main() {
@@ -55,8 +56,9 @@ func main() {
 		}
 		state.value = walkItem.Value
 		state.path = walkItem.Path
-		for _, cmd := range state.program {
-			cmd.exec(&state)
+		state.pc = 0
+		for state.pc < len(state.program) {
+			state.program[state.pc].exec(&state)
 		}
 		if !quiet {
 			pathValues, err := walk.Compound(state.path)
diff --git a/main/parse.go b/main/parse.go
index 1972b66..ef50e81 100644
--- a/main/parse.go
+++ b/main/parse.go
@@ -57,18 +57,18 @@ func (p *parser) parseSubex() subex.SubexAST {
 	return subexAST
 }
 
-func (p *parser) parseBasicCommand(commandChar rune) Command {
+func (p *parser) parseBasicCommand(commands []Command, commandChar rune) []Command {
 	switch commandChar {
 		case 'p':
-			return PrintValueCommand{}
+			return append(commands, PrintValueCommand{})
 		case 'd':
-			return DeleteValueCommand{}
+			return append(commands, DeleteValueCommand{})
 		case 'D':
-			return DeletePathCommand{}
+			return append(commands, DeletePathCommand{})
 		case 'n':
-			return NextCommand{}
+			return append(commands, NextCommand{})
 		case 'N':
-			return AppendNextCommand{}
+			return append(commands, AppendNextCommand{})
 		case 's', 'S', 'f', 'F', 'l', 'L', 'a', 'A':
 			ast := p.parseSubex()
 			switch commandChar {
@@ -120,77 +120,67 @@ func (p *parser) parseBasicCommand(commandChar rune) Command {
 					}
 			}
 			subex := subex.CompileTransducer(ast)
-			var next Command
-			token := p.peek()
-			switch token.typ {
-				case TokenEOF, TokenRBrace:
-					next = NoopCommand{}
-				default:
-					next = p.parseCommand()
-			}
 			switch commandChar {
 				case 's', 'a':
-					return SubstituteValueCommand {subex, next}
+					return append(commands, SubstituteValueCommand {subex}, JumpCommand {len(commands) + 3})
 				case 'S', 'f', 'F', 'l', 'L', 'A':
-					return SubstitutePathCommand {subex, next}
+					return append(commands, SubstitutePathCommand {subex}, JumpCommand {len(commands) + 3})
 				default:
 					panic("Unreachable!?!?")
 			}
 		case 'o':
-			return NoopCommand{}
+			return append(commands, NoopCommand{})
 		case 'x':
-			return SwapXRegCommand{}
+			return append(commands, SwapXRegCommand{})
 		case 'X':
-			return AppendXRegCommand{}
+			return append(commands, AppendXRegCommand{})
 		case 'y':
-			return SwapYRegCommand{}
+			return append(commands, SwapYRegCommand{})
 		case 'Y':
-			return AppendYRegCommand{}
+			return append(commands, AppendYRegCommand{})
 		case 'z':
-			return SwapZRegCommand{}
+			return append(commands, SwapZRegCommand{})
 		case 'Z':
-			return AppendZRegCommand{}
+			return append(commands, AppendZRegCommand{})
 		case 'k':
-			return SwapPathCommand{}
+			return append(commands, SwapPathCommand{})
 		case 'K':
-			return AppendPathCommand{}
+			return append(commands, AppendPathCommand{})
 		default:
 			panic("Invalid command")
 	}
 }
 
-func (p *parser) parseCommand() Command {
+func (p *parser) parseCommand(commands []Command) []Command {
 	token := p.next()
 	switch token.typ {
 		case TokenLBrace:
-			commands := p.parseCommands()
+			jumpToBlockCommand := &JumpCommand{0}
+			commands = append(commands, JumpCommand {len(commands) + 2}, jumpToBlockCommand)
+			commands = p.parseCommands(commands)
 			if p.next().typ != TokenRBrace {
 				panic("Missing matching }")
 			}
-			return SequenceCommand {commands}
+			jumpToBlockCommand.destination = len(commands)
+			return commands
 		case TokenCommand:
 			commandChar, _, err := strings.NewReader(token.val).ReadRune()
 			if err != nil {
 				panic("Error reading a command character!?")
 			}
-			return p.parseBasicCommand(commandChar)
+			return p.parseBasicCommand(commands, commandChar)
 		default:
 			panic("Invalid token, expected command")
 	}
 }
 
-func (p *parser) parseCommands() []Command {
-	var commands []Command
+func (p *parser) parseCommands(commands []Command) []Command {
 	for {
 		nextToken := p.peek()
 		if nextToken.typ == TokenEOF || nextToken.typ == TokenRBrace {
 			return commands
 		}
-		commands = append(commands, p.parseCommand())
-		endToken := p.peek()
-		if endToken.typ == TokenEOF || endToken.typ == TokenRBrace {
-			return commands
-		}
+		commands = p.parseCommand(commands)
 	}
 }
 
@@ -198,5 +188,5 @@ func Parse(tokens chan Token) []Command {
 	p := parser {
 		tokenStream: tokens,
 	}
-	return p.parseCommands()
+	return p.parseCommands(nil)
 }