diff --git a/examples/d/README.md b/examples/d/README.md
index 86cb10a8..eed3494c 100644
--- a/examples/d/README.md
+++ b/examples/d/README.md
@@ -9,7 +9,7 @@ afterwards.
 The usual calculator.
 
 ## d/calc.y
-A richer implementation of the calculator.
+A richer implementation of the calculator, with location tracking.
 
 <!---
 
diff --git a/examples/d/calc/calc.test b/examples/d/calc/calc.test
index 6b237592..b592d215 100644
--- a/examples/d/calc/calc.test
+++ b/examples/d/calc/calc.test
@@ -33,4 +33,19 @@ run 0 5
 cat >input <<EOF
 1 + 2 * * 3
 EOF
-run 1 "err: syntax error, unexpected *, expecting + or - or ( or number"
+run 1 "err: 1.9: syntax error, unexpected *, expecting + or - or ( or number"
+
+cat >input <<EOF
+1111 + 1111 2222
+EOF
+run 1 "err: 1.13-16: syntax error, unexpected number"
+
+cat >input <<EOF
+1 +
+EOF
+run 1 "err: 1.4-2.0: syntax error, unexpected end of line, expecting + or - or ( or number"
+
+cat >input <<EOF
+99 009
+EOF
+run 1 "err: 1.4-6: syntax error, unexpected number"
diff --git a/examples/d/calc/calc.y b/examples/d/calc/calc.y
index 15b4f7c7..0aa96ee6 100644
--- a/examples/d/calc/calc.y
+++ b/examples/d/calc/calc.y
@@ -22,6 +22,8 @@
 %define api.parser.class {Calc}
 %define parse.error verbose
 
+%locations
+
 %union {
   int ival;
 }
@@ -94,13 +96,16 @@ class CalcLexer(R) : Lexer
 
   this(R r) { input = r; }
 
+  YYPosition start;
+  YYPosition end;
+
   // Should be a local in main, shared with %parse-param.
   int exit_status = 0;
 
-  public void yyerror (string s)
+  void yyerror(YYLocation loc, string s)
   {
     exit_status = 1;
-    stderr.writeln (s);
+    stderr.writeln(loc.toString(), ": ", s);
   }
 
   YYSemanticType semanticVal_;
@@ -116,24 +121,39 @@ class CalcLexer(R) : Lexer
 
     // Skip initial spaces
     while (!input.empty && input.front != '\n' && isWhite (input.front))
+    {
+      start = end;
+      end.column++;
       input.popFront;
+    }
 
     if (input.empty)
       return TokenKind.YYEOF;
 
     // Numbers.
     if (input.front.isNumber)
+    {
+      int lenChars = 0;
+      auto copy = input;
+      import std.conv : parse;
+      semanticVal_.ival = input.parse!int;
+      while (!input.empty && copy.front != input.front)
       {
-        import std.conv : parse;
-        semanticVal_.ival = input.parse!int;
-        return TokenKind.NUM;
+        lenChars++;
+        copy.popFront;
       }
+      start = end;
+      end.column += lenChars;
+      return TokenKind.NUM;
+    }
 
     // Individual characters
     auto ch = input.front;
     input.popFront;
+    start = end;
+    end.column++;
     switch (ch)
-      {
+    {
       case '=':  return TokenKind.EQ;
       case '+':  return TokenKind.PLUS;
       case '-':  return TokenKind.MINUS;
@@ -141,9 +161,24 @@ class CalcLexer(R) : Lexer
       case '/':  return TokenKind.SLASH;
       case '(':  return TokenKind.LPAR;
       case ')':  return TokenKind.RPAR;
-      case '\n': return TokenKind.EOL;
-      default: assert(0);
+      case '\n':
+      {
+        end.line++;
+        end.column = 1;
+        return TokenKind.EOL;
       }
+      default: assert(0);
+    }
+  }
+
+  YYPosition startPos() const
+  {
+    return start;
+  }
+
+  YYPosition endPos() const
+  {
+    return end;
   }
 }