First draft of Scanning.

Also:

- Tweak some styles.
- Allow markers in code to line up asides.

asset/sass/chapter.scss

@@ -99,9 +99,13 @@ article.chapter {
   .design-note {
     background: hsl(80, 30%, 96%);
 
-    code, pre {
+    code, .codehilite {
       background: hsl(80, 20%, 93%);
     }
+
+    .codehilite {
+      margin: -12px 0 -12px -12px;
+    }
   }
 }
 

asset/style.scss

@@ -357,7 +357,7 @@ aside {
     padding: 1px 2px;
   }
 
-  pre {
+  .codehilite {
     padding: 6px;
     margin: -12px 0;
   }

java/com/craftinginterpreters/lox/Lox.java

@@ -27,7 +27,7 @@ public static void main(String[] args) throws IOException {
     } else if (args.length == 1) {
       runFile(args[0]);
     } else {
-      repl();
+      runPrompt();
     }
   }
 //> run-file
@@ -44,17 +44,23 @@ private static void runFile(String path) throws IOException {
 //< Evaluating Expressions not-yet
   }
 //< run-file
-//> repl
-  private static void repl() throws IOException {
+//> prompt
+  private static void runPrompt() throws IOException {
     InputStreamReader input = new InputStreamReader(System.in);
     BufferedReader reader = new BufferedReader(input);
 
-    for (;;) {
+    for (;;) { // [repl]
       System.out.print("> ");
       run(reader.readLine());
+//> reset-had-error
+      hadError = false;
+//< reset-had-error
+//> Evaluating Expressions not-yet
+      hadRuntimeError = false;
+//< Evaluating Expressions not-yet
     }
   }
-//< repl
+//< prompt
 //> run
   private static void run(String source) {
     Scanner scanner = new Scanner(source);

java/com/craftinginterpreters/lox/Scanner.java

@@ -8,7 +8,7 @@
 
 import static com.craftinginterpreters.lox.TokenType.*;
 
-class Scanner {
+class Scanner { // [files]
 //> keyword-map
   private static final Map<String, TokenType> keywords;
 
@@ -78,7 +78,8 @@ private void scanToken() {
 //> slash
       case '/':
         if (match('/')) {
-          comment();
+          // A comment goes until the end of the line.
+          while (peek() != '\n' && !isAtEnd()) advance();
         } else {
           addToken(SLASH);
         }
@@ -122,12 +123,6 @@ private void scanToken() {
     }
   }
 //< scan-token
-//> comment
-  private void comment() {
-    // A comment goes until the end of the line.
-    while (peek() != '\n' && !isAtEnd()) advance();
-  }
-//< comment
 //> identifier
   private void identifier() {
     while (isAlphaNumeric(peek())) advance();
@@ -157,9 +152,8 @@ private void number() {
       while (isDigit(peek())) advance();
     }
 
-    double value = Double.parseDouble(
-        source.substring(start, current));
-    addToken(NUMBER, value);
+    addToken(NUMBER,
+        Double.parseDouble(source.substring(start, current)));
   }
 //< number
 //> string
@@ -218,7 +212,7 @@ private boolean isAlphaNumeric(char c) {
 //> is-digit
   private boolean isDigit(char c) {
     return c >= '0' && c <= '9';
-  }
+  } // [is-digit]
 //< is-digit
 //> is-at-end
   private boolean isAtEnd() {

java/com/craftinginterpreters/lox/Token.java

@@ -5,7 +5,7 @@ class Token {
   final TokenType type;
   final String lexeme;
   final Object literal;
-  final int line;
+  final int line; // [location]
 
   Token(TokenType type, String lexeme, Object literal, int line) {
     this.type = type;

note/chapter/parsing-expressions.md

@@ -38,3 +38,11 @@ https://www.cs.cmu.edu/~pattis/misc/ebnf.pdf
   - is an empty source file a valid program?
   - write the bnf for a language you know. if the language is complex, just do
     an interesting subset. what parts are hard?
+
+--
+
+error recovery:
+
+The tricky part, of course, is that the first error may *cause* later **cascaded errors**. For example, if they accidentally started a string with `'` instead of `"`, then the rest of the string literal will likely cause a number of bogus syntax errors when the scanner and parser tries to treat it like code.
+
+There is an art, called **error recovery** to getting back to a good state after an error is found to minimize the number of later spurious errors. We'll talk more about it during parsing.

note/log.txt

@@ -1,3 +1,9 @@
+2017/01/01 - 772 words design note for scanner, aside markers in code
+2016/12/31 - 1081 words first draft scanner, mostly done
+2016/12/30 - 1085 words first draft scanner
+2016/12/29 - 722 words first draft scanner
+2016/12/28 - 561 words first draft scanner
+2016/12/27 - 1127 words first draft scanner
 2016/12/26 - finish outlining and splitting, reallow multiline strings
 2016/12/25 - fix some bugs in chapter splitting, make multiline strings and error
 2016/12/24 - slice up more scanning code into snippets

site/contents.html

@@ -118,7 +118,6 @@ <h4><a href="the-lox-language.html#design-note">Design Note: Statements and Expr
 <h2><span class="num">II.</span><a href="a-tree-walk-interpreter-in-java.html" name="a-tree-walk-interpreter-in-java">A Tree-Walk Interpreter in Java</a></h2>
   <ol start="4">
     <li><h3><a href="scanning.html">Scanning</a>
-      <a class="not-written" href="#not-written" title="This chapter hasn't been written yet">(coming soon!)</a>
 </h3>
     <p>
     <span class="topic">Tokens</span>
@@ -129,6 +128,7 @@ <h2><span class="num">II.</span><a href="a-tree-walk-interpreter-in-java.html" n
     <span class="topic">Reserved words</span>
     <span class="topic">Error reporting</span>
     </p>
+    <h4><a href="scanning.html#design-note">Design Note: Implicit Semicolons</a></h4>
     </li>
     <li><h3><a href="representing-code.html">Representing Code</a>
       <a class="not-written" href="#not-written" title="This chapter hasn't been written yet">(coming soon!)</a>