From 19235b59a39e82d5714ac60d8c5665bd44a0278f Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 8 Jul 2023 20:55:35 +0100
Subject: Parse subtraction

---
 .../java/org/shedlang/compiler/parser/Parser.java  | 36 ++++++++++++++++++++--
 .../org/shedlang/compiler/parser/TokenType.java    |  1 +
 .../org/shedlang/compiler/parser/Tokeniser.java    | 13 ++++----
 3 files changed, 42 insertions(+), 8 deletions(-)

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/parser/Parser.java b/src/main/java/org/shedlang/compiler/parser/Parser.java
index dcb06eb0..d6cef7d4 100644
--- a/src/main/java/org/shedlang/compiler/parser/Parser.java
+++ b/src/main/java/org/shedlang/compiler/parser/Parser.java
@@ -21,10 +21,24 @@ public class Parser {
     private static UntypedExpressionNode parseAdd(
         UntypedExpressionNode left,
         TokenIterator<TokenType> tokens
+    ) {
+        return parseBinaryOperation(
+            TokenType.SYMBOL_PLUS,
+            UntypedBinaryOperator.ADD,
+            left,
+            tokens
+        );
+    }
+
+    private static UntypedExpressionNode parseBinaryOperation(
+        TokenType operatorTokenType,
+        UntypedBinaryOperator operator,
+        UntypedExpressionNode left,
+        TokenIterator<TokenType> tokens
     ) {
         var start = left.source().start();
 
-        tokens.skip(TokenType.SYMBOL_PLUS);
+        tokens.skip(operatorTokenType);
 
         // TODO: precedence
         var right = parseTopLevelExpression(tokens);
@@ -33,7 +47,7 @@ public class Parser {
         var source = start.to(end);
 
         return new UntypedBinaryOperationNode(
-            UntypedBinaryOperator.ADD,
+            operator,
             left,
             right,
             source
@@ -307,6 +321,18 @@ public class Parser {
         };
     }
 
+    private static UntypedExpressionNode parseSub(
+        UntypedExpressionNode left,
+        TokenIterator<TokenType> tokens
+    ) {
+        return parseBinaryOperation(
+            TokenType.SYMBOL_MINUS,
+            UntypedBinaryOperator.SUB,
+            left,
+            tokens
+        );
+    }
+
     static UntypedExpressionNode parseTopLevelExpression(TokenIterator<TokenType> tokens) {
         var left = parsePrimaryExpression(tokens);
 
@@ -316,9 +342,15 @@ public class Parser {
                 case SYMBOL_PLUS -> {
                     left = parseAdd(left, tokens);
                 }
+
+                case SYMBOL_MINUS -> {
+                    left = parseSub(left, tokens);
+                }
+
                 case SYMBOL_BANG, SYMBOL_PAREN_OPEN -> {
                     left = parseCall(left, tokens);
                 }
+
                 default -> {
                     return left;
                 }
diff --git a/src/main/java/org/shedlang/compiler/parser/TokenType.java b/src/main/java/org/shedlang/compiler/parser/TokenType.java
index c55f7149..9f439e03 100644
--- a/src/main/java/org/shedlang/compiler/parser/TokenType.java
+++ b/src/main/java/org/shedlang/compiler/parser/TokenType.java
@@ -20,6 +20,7 @@ public enum TokenType {
     SYMBOL_COMMA,
     SYMBOL_DOT,
     SYMBOL_EQUALS,
+    SYMBOL_MINUS,
     SYMBOL_PAREN_OPEN,
     SYMBOL_PAREN_CLOSE,
     SYMBOL_PLUS,
diff --git a/src/main/java/org/shedlang/compiler/parser/Tokeniser.java b/src/main/java/org/shedlang/compiler/parser/Tokeniser.java
index c26c512a..2f967452 100644
--- a/src/main/java/org/shedlang/compiler/parser/Tokeniser.java
+++ b/src/main/java/org/shedlang/compiler/parser/Tokeniser.java
@@ -22,6 +22,11 @@ public class Tokeniser {
     private static final RegexTokeniser<TokenType> tokeniser = new RegexTokeniser<>(
         TokenType.UNKNOWN,
         List.of(
+            RegexTokeniser.rule(TokenType.IDENTIFIER, "[A-Za-z][A-Za-z0-9]*"),
+            RegexTokeniser.rule(TokenType.INT, "-?[0-9]+"),
+            RegexTokeniser.rule(TokenType.STRING, "\"(?:[^\\\\\"\n\r]|\\\\.)*\""),
+            RegexTokeniser.rule(TokenType.WHITESPACE, "[\r\n\t ]+"),
+
             RegexTokeniser.rule(TokenType.SYMBOL_THIN_ARROW, "->"),
 
             RegexTokeniser.rule(TokenType.SYMBOL_BANG, "!"),
@@ -31,15 +36,11 @@ public class Tokeniser {
             RegexTokeniser.rule(TokenType.SYMBOL_COMMA, ","),
             RegexTokeniser.rule(TokenType.SYMBOL_DOT, "\\."),
             RegexTokeniser.rule(TokenType.SYMBOL_EQUALS, "="),
+            RegexTokeniser.rule(TokenType.SYMBOL_MINUS, "-"),
             RegexTokeniser.rule(TokenType.SYMBOL_PAREN_OPEN, "\\("),
             RegexTokeniser.rule(TokenType.SYMBOL_PAREN_CLOSE, "\\)"),
             RegexTokeniser.rule(TokenType.SYMBOL_PLUS, "\\+"),
-            RegexTokeniser.rule(TokenType.SYMBOL_SEMICOLON, ";"),
-
-            RegexTokeniser.rule(TokenType.IDENTIFIER, "[A-Za-z][A-Za-z0-9]*"),
-            RegexTokeniser.rule(TokenType.INT, "-?[0-9]+"),
-            RegexTokeniser.rule(TokenType.STRING, "\"(?:[^\\\\\"\n\r]|\\\\.)*\""),
-            RegexTokeniser.rule(TokenType.WHITESPACE, "[\r\n\t ]+")
+            RegexTokeniser.rule(TokenType.SYMBOL_SEMICOLON, ";")
         )
     );
 
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