From 9c1baf8216d451b84f27b8b6505cdd6e9efa0fb1 Mon Sep 17 00:00:00 2001
From: Sasha Koshka <sashakoshka@tebibyte.media>
Date: Wed, 10 Aug 2022 14:18:28 -0400
Subject: [PATCH] Lexer can now tokenize minus decrement return direction
 separator

---
 file/error.go  |  1 +
 lexer/lexer.go | 26 +++++++++++++++++++++-----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/file/error.go b/file/error.go
index e6b4d80..6a0d502 100644
--- a/file/error.go
+++ b/file/error.go
@@ -59,6 +59,7 @@ func (err Error) Error () (formattedMessage string) {
 		// print an arrow with a tail spanning the width of the mistake
 		columnCountdown := err.Location.column
 		for columnCountdown > 1 {
+			// TODO: for tabs, print out a teb instead.
 			formattedMessage += " "
 			columnCountdown --
 		}
diff --git a/lexer/lexer.go b/lexer/lexer.go
index 00959b0..60795ef 100644
--- a/lexer/lexer.go
+++ b/lexer/lexer.go
@@ -126,13 +126,10 @@ func (lexer *LexingOperation) tokenizeSymbolBeginning () (err error) {
 		})
 		lexer.nextRune()
 	case '+':
-		lexer.addToken (Token {
-			kind: TokenKindPlus,
-		})
+		// TODO: tokenize plus begin
 		lexer.nextRune()
 	case '-':
-		// TODO: tokenize dash begin
-		lexer.nextRune()
+		lexer.tokenizeDashBeginning()
 	case '*':
 		lexer.addToken (Token {
 			kind: TokenKindAsterisk,
@@ -187,6 +184,25 @@ func (lexer *LexingOperation) tokenizeSymbolBeginning () (err error) {
 	return
 }
 
+func (lexer *LexingOperation) tokenizeDashBeginning () (err error) {
+	token := Token { kind: TokenKindMinus }
+	lexer.nextRune()
+	
+	if lexer.char == '-' {
+		token.kind = TokenKindDecrement
+		lexer.nextRune()
+	} else if lexer.char == '>' {
+		token.kind = TokenKindReturnDirection
+		lexer.nextRune()
+	}
+
+	if lexer.char == '-' {
+		token.kind = TokenKindSeparator
+		lexer.nextRune()
+	}
+	return
+}
+
 // addToken adds a new token to the lexer's token slice.
 func (lexer *LexingOperation) addToken (token Token) {
 	lexer.tokens = append(lexer.tokens, token)