From 0720fd8ed0aa92248622a9f3c3ebd522b002fd91 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Wed, 11 Nov 2026 15:40:22 -0800
Subject: graphic tictactoe

Hex & octal digits
---
 .../com/seaofnodes/simple/parser/Expressions.java  |  2 +-
 .../java/com/seaofnodes/simple/parser/Lexer.java   | 26 +++++++++++++++++++++-
 2 files changed, 26 insertions(+), 2 deletions(-)

(limited to 'chapter31/src/main/java/com')

diff --git a/chapter31/src/main/java/com/seaofnodes/simple/parser/Expressions.java b/chapter31/src/main/java/com/seaofnodes/simple/parser/Expressions.java
index 247d974e..6486aba8 100644
--- a/chapter31/src/main/java/com/seaofnodes/simple/parser/Expressions.java
+++ b/chapter31/src/main/java/com/seaofnodes/simple/parser/Expressions.java
@@ -400,7 +400,7 @@ final class Expressions {
      * Parse integer literal
      *
      * <pre>
-     *     integerLiteral: [1-9][0-9]* | [0]
+     *     integerLiteral: [1-9][0-9]* | 0[0-7]* | 0[xX][0-9a-fA-F]+
      *     floatLiteral: [digits].[digits]?[e [digits]]?[f]?
      * </pre>
      */
diff --git a/chapter31/src/main/java/com/seaofnodes/simple/parser/Lexer.java b/chapter31/src/main/java/com/seaofnodes/simple/parser/Lexer.java
index 5e4b7311..9ab678ca 100644
--- a/chapter31/src/main/java/com/seaofnodes/simple/parser/Lexer.java
+++ b/chapter31/src/main/java/com/seaofnodes/simple/parser/Lexer.java
@@ -239,6 +239,7 @@ public class Lexer {
     // Return a constant Type, either TypeInteger or TypeFloat
     Type parseNumber() {
         Lexer start=new Lexer(this);
+        if( isHex() ) return parseInteger(parseNumberString(),16,2,start);
         int old = _position;
         int len = isLongOrDouble();
         boolean f32 = peek()=='f';
@@ -250,7 +251,7 @@ public class Lexer {
                 return TypeFloat.constant(Float.parseFloat(literal));
             if( len > 0 ) {
                 if( len > 1 && _input[old]=='0' )
-                    throw Parser.error("Syntax error: integer values cannot start with '0'",start);
+                    return parseInteger(literal,8,0,start);
                 long i = Long.parseLong(literal);
                 return TypeInteger.constant(i);
             }
@@ -262,6 +263,11 @@ public class Lexer {
     }
     private String parseNumberString() {
         int old = _position;
+        if( isHex() ) {
+            _position += 2;
+            while( isIdLetter(peek()) ) inc();
+            return new String(_input,old,_position-old);
+        }
         int len = Math.abs(isLongOrDouble());
         if( peek()=='f' ) {
             nextChar();
@@ -270,6 +276,24 @@ public class Lexer {
         return new String(_input,old,len);
     }
 
+    private boolean isHex() {
+        return peek()=='0' && _position+1<_input.length && (peek(1)=='x' || peek(1)=='X');
+    }
+
+    private TypeInteger parseInteger(String literal, int radix, int prefix, Lexer start) {
+        String kind = radix==16 ? "Hexadecimal" : "Octal";
+        if( literal.length()==prefix )
+            throw Parser.error(kind+" integer literal requires at least one digit",start);
+        for( int i=prefix; i<literal.length(); i++ )
+            if( Character.digit(literal.charAt(i),radix)<0 )
+                throw Parser.error("Invalid "+kind.toLowerCase()+" integer literal '"+literal+"'",start);
+        try {
+            return TypeInteger.constant(Long.parseUnsignedLong(literal.substring(prefix),radix));
+        } catch( NumberFormatException ex ) {
+            throw Parser.error(kind+" integer literal exceeds 64 bits",start);
+        }
+    }
+
     // Return +len that ends a long
     // Return -len that ends a double
     private int isLongOrDouble() {
-- 
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