From 39f767aef901694eef14b1004b13756410f19f66 Mon Sep 17 00:00:00 2001
From: Charlie Stanton <charlie@shtanton.xyz>
Date: Wed, 26 Apr 2023 15:02:03 +0100
Subject: Add labels and branches with the : and b commands
---
main/command.go | 12 ++++++++++++
main/lex.go | 10 ++++++++++
main/parse.go | 34 ++++++++++++++++++++++++++++++++--
3 files changed, 54 insertions(+), 2 deletions(-)
(limited to 'main')
diff --git a/main/command.go b/main/command.go
index 44fd9eb..63cc3b8 100644
--- a/main/command.go
+++ b/main/command.go
@@ -207,4 +207,16 @@ func (cmd JumpCommand) exec(state *ProgramState) {
}
func (cmd JumpCommand) String() string {
return fmt.Sprintf("b%v", cmd.destination)
+}
+
+// Placeholder as the branch destination may not have been parsed when the branch command is
+// Should never appear in a program to actually be run
+type BranchPlaceholderCommand struct {
+ label rune
+}
+func (cmd BranchPlaceholderCommand) exec(state *ProgramState) {
+ panic("Tried to execute a BranchPlaceholderCommand!!!")
+}
+func (cmd BranchPlaceholderCommand) String() string {
+ return fmt.Sprintf("b%c", cmd.label)
}
\ No newline at end of file
diff --git a/main/lex.go b/main/lex.go
index f28244d..198c346 100644
--- a/main/lex.go
+++ b/main/lex.go
@@ -118,6 +118,7 @@ const (
TokenCommand // A command character
TokenSubstituteDelimiter // usually / but could be something else
TokenSubex // A subex
+ TokenLabel // A label
)
type Token struct {
@@ -182,6 +183,9 @@ func lexCommand(l *lexer) stateFunc {
case 's', 'S', 'f', 'F', 'l', 'L', 'a', 'A':
l.emit(TokenCommand)
return lexSubstitution
+ case ':', 'b':
+ l.emit(TokenCommand)
+ return lexLabel
}
if isAlpha(r) {
l.emit(TokenCommand)
@@ -212,3 +216,9 @@ func lexSubstitution(l *lexer) stateFunc {
}
return lexCommand
}
+
+func lexLabel(l *lexer) stateFunc {
+ l.next()
+ l.emit(TokenLabel)
+ return lexCommand
+}
diff --git a/main/parse.go b/main/parse.go
index ef50e81..cbbfb9a 100644
--- a/main/parse.go
+++ b/main/parse.go
@@ -1,14 +1,16 @@
package main
import (
- "strings"
"fmt"
"main/subex"
+ "strings"
+ "unicode/utf8"
)
type parser struct {
tokenStream chan Token
rewinds []Token
+ labels map[rune]int
}
func (p *parser) next() Token {
var token Token
@@ -146,6 +148,21 @@ func (p *parser) parseBasicCommand(commands []Command, commandChar rune) []Comma
return append(commands, SwapPathCommand{})
case 'K':
return append(commands, AppendPathCommand{})
+ case ':':
+ labelToken := p.next()
+ if labelToken.typ != TokenLabel {
+ panic("Missing branch label")
+ }
+ label, _ := utf8.DecodeRuneInString(labelToken.val)
+ p.labels[label] = len(commands)
+ return commands
+ case 'b':
+ labelToken := p.next()
+ if labelToken.typ != TokenLabel {
+ panic("Missing branch label")
+ }
+ label, _ := utf8.DecodeRuneInString(labelToken.val)
+ return append(commands, BranchPlaceholderCommand {label})
default:
panic("Invalid command")
}
@@ -187,6 +204,19 @@ func (p *parser) parseCommands(commands []Command) []Command {
func Parse(tokens chan Token) []Command {
p := parser {
tokenStream: tokens,
+ rewinds: nil,
+ labels: make(map[rune]int),
+ }
+ program := p.parseCommands(nil)
+ for i, command := range program {
+ switch branch := command.(type) {
+ case BranchPlaceholderCommand:
+ destination, exists := p.labels[branch.label]
+ if !exists {
+ panic("Tried to branch to a label that doesn't exist")
+ }
+ program[i] = JumpCommand {destination}
+ }
}
- return p.parseCommands(nil)
+ return program
}
--
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