3 files changed, 44 insertions, 52 deletions

diff --git a/main/command.go b/main/command.go
index 7d44309..5e77dd0 100644
--- a/main/command.go
+++ b/main/command.go
@@ -5,6 +5,10 @@ import (
 	"main/subex"
 )
 
+type Command interface {
+	exec(*ProgramState)
+}
+
 type PrintValueCommand struct {}
 func (cmd PrintValueCommand) exec(state *ProgramState) {
 	path := walk.PathFromWalkValues(state.path)
@@ -45,33 +49,50 @@ func (cmd DeleteAllCommand) exec(state *ProgramState) {
 	state.value = nil
 }
 
-type SubstituteCommand struct {
-	subex subex.SubexState
-	next Command
-}
-func (cmd SubstituteCommand) exec(state *ProgramState) {
+func runSubex(state subex.SubexState, in []walk.WalkValue) (out []walk.WalkValue, error bool) {
 	valueStream := make(chan walk.WalkValue)
 	go func(in []walk.WalkValue, out chan<- walk.WalkValue) {
 		for _, value := range in {
 			out <- value
 		}
 		close(out)
-	}(state.value, valueStream)
+	}(in, valueStream)
 	atomStream := walk.Atomise(valueStream)
-	atomsOut, error := subex.RunTransducer(cmd.subex, atomStream)
+	atomsOut, error := subex.RunTransducer(state, atomStream)
 	if error {
-		return
+		return nil, true
 	}
 	valuesOut, err := walk.MemoryCompound(atomsOut)
 	if err != nil {
+		return nil, true
+	}
+	return valuesOut, false
+}
+
+type SubstituteValueCommand struct {
+	subex subex.SubexState
+	next Command
+}
+func (cmd SubstituteValueCommand) exec(state *ProgramState) {
+	newValue, err := runSubex(cmd.subex, state.value)
+	if err {
 		return
 	}
-	state.value = valuesOut
+	state.value = newValue
 	cmd.next.exec(state)
 }
 
-type Command interface {
-	exec(*ProgramState)
+type SubstitutePathCommand struct {
+	subex subex.SubexState
+	next Command
+}
+func (cmd SubstitutePathCommand) exec(state *ProgramState) {
+	newPath, err := runSubex(cmd.subex, state.path)
+	if err {
+		return
+	}
+	state.path = newPath
+	cmd.next.exec(state)
 }
 
 type NoopCommand struct {}
diff --git a/main/lex.go b/main/lex.go
index e93e42a..2826b1e 100644
--- a/main/lex.go
+++ b/main/lex.go
@@ -113,39 +113,10 @@ type TokenType int
 const (
 	TokenErr TokenType = iota // Lexing error
 	TokenEOF // end of file
-	TokenLParen // (
-	TokenRParen // )
 	TokenLBrace // {
 	TokenRBrace // }
-	TokenLBrack // [
-	TokenRBrack // ]
 	TokenCommand // A command character
-	TokenHash // #
-	TokenAt // @
-	TokenDot // .
-	TokenAst // *
-	TokenBar // |
-	TokenOr // ||
-	TokenAnd // &&
-	TokenHat // ^
-	TokenDollar // $
-	TokenQuestion // ?
-	TokenHatDollar // ^$
-	TokenExclamation // !
-	TokenTilde // ~
-	TokenDoubleQuote // "
-	TokenStringLiteral // A string literal, not including the " either side
-	TokenNullLiteral // null
-	TokenTrueLiteral // true
-	TokenFalseLiteral // false
-	TokenColon // :
-	TokenComma // ,
 	TokenSubstituteDelimiter // usually / but could be something else
-	TokenSubstitutePlaceholder // \1, \2 etc.
-	TokenTerminalLiteral // One of {, }, [, ]
-	TokenNumberLiteral // A number literal
-	TokenPatternStringIndex // A string index in a pattern
-	TokenPatternIntegerIndex // An integer index in a pattern
 	TokenSubex // A subex
 )
 
@@ -208,7 +179,7 @@ func lexCommand(l *lexer) stateFunc {
 		case '}':
 			l.emit(TokenRBrace)
 			return lexCommand
-		case 's':
+		case 's', 'S':
 			l.emit(TokenCommand)
 			return lexSubstitution
 	}
diff --git a/main/parse.go b/main/parse.go
index e9dd012..7c87d15 100644
--- a/main/parse.go
+++ b/main/parse.go
@@ -33,13 +33,6 @@ func (p *parser) peek() Token {
 	return token
 }
 
-var segmentTokens map[TokenType]bool = map[TokenType]bool {
-	TokenHash: true,
-	TokenAt: true,
-	TokenDot: true,
-	TokenLBrack: true,
-}
-
 func (p *parser) parseSubex() subex.SubexState {
 	delim := p.next()
 	if delim.typ != TokenSubstituteDelimiter {
@@ -69,7 +62,7 @@ func (p *parser) parseBasicCommand(commandChar rune) Command {
 			return NextCommand{}
 		case 'N':
 			return AppendNextCommand{}
-		case 's':
+		case 's', 'S':
 			subex := p.parseSubex()
 			var next Command
 			token := p.peek()
@@ -79,9 +72,16 @@ func (p *parser) parseBasicCommand(commandChar rune) Command {
 				default:
 					next = p.parseCommand()
 			}
-			return SubstituteCommand {
-				subex: subex,
-				next: next,
+			if (commandChar == 's') {
+				return SubstituteValueCommand {
+					subex: subex,
+					next: next,
+				}
+			} else {
+				return SubstitutePathCommand {
+					subex: subex,
+					next: next,
+				}
 			}
 		case 'o':
 			return NoopCommand{}