grabbing an old version of the read library from beyond the grave of the moby probject

js-assembler/runtime-src/read.js

@@ -0,0 +1,161 @@
+var readSchemeExpressions;
+
+
+function tokenize(s) {
+
+  function replaceEscapes(s) {
+    return s.replace(/\\./g, function(match, submatch, index) {
+      // FIXME: add more escape sequences.
+      if (match == '\\n') {
+	return "\n";
+      }
+      else {
+	return match.substring(1);
+      }
+      });
+    }
+
+
+
+  var tokens = [];
+
+  var PATTERNS = [['whitespace' , /^(\s+)/],
+		  ['comment' , /(^;[^\n]*)/],
+		  ['(' , /^(\(|\[)/],
+		  [')' , /^(\)|\])/],
+	          ['\'' , /^(\')/],
+		  ['`' , /^(`)/],
+		  [',' , /^(,)/],
+		  ['char', /^\#\\(newline)/],
+                  ['char', /^\#\\(.)/],
+		  ['number' , /^([+\-]?(?:\d+\.\d+|\d+\.|\.\d+|\d+))/],
+		  ['string' , /^"((?:([^\\"]|(\\.)))*)"/],      // comment (emacs getting confused with quote): " 
+		  ['symbol' ,/^([a-zA-Z\:\+\=\~\_\?\!\@\#\$\%\^\&\*\-\/\.\>\<][\w\:\+\=\~\_\?\!\@\#\$\%\^\&\*\-\/\.\>\<]*)/]
+		 ];
+
+  while (true) {
+    var shouldContinue = false;
+    for (var i = 0; i < PATTERNS.length; i++) {
+      var patternName = PATTERNS[i][0];
+      var pattern = PATTERNS[i][1]
+      var result = s.match(pattern);
+      if (result != null) {
+	if (patternName == 'string') {
+	  result[1] = replaceEscapes(result[1]);
+        }
+	if (patternName != 'whitespace' && patternName != 'comment') {
+	  tokens.push([patternName, result[1]]);
+	}
+	s = s.substring(result[0].length);
+	shouldContinue = true;
+      }
+    }
+    if (! shouldContinue) {
+      break;
+    }
+  }
+  return [tokens, s];
+}
+
+
+
+
+(function(){
+
+
+  readSchemeExpressions = function(s) {
+    var tokensAndError = tokenize(s);
+    var tokens = tokensAndError[0];
+    if (tokensAndError[1].length > 0) {
+	throw new Error("Error while tokenizing: the rest of the stream is: " + tokensAndError[1]);
+    }
+
+    var quoteSymbol = plt.types.Symbol.makeInstance("quote");
+    var quasiquoteSymbol = plt.types.Symbol.makeInstance("quasiquote");
+    var unquoteSymbol = plt.types.Symbol.makeInstance("unquote");
+    var empty = plt.types.Empty.EMPTY;
+
+    function isType(type) {
+      return (tokens.length > 0 && tokens[0][0] == type);
+    }
+    
+    function eat(expectedType) {
+      if (tokens.length == 0)
+	throw new Error("token stream exhausted while trying to eat " +
+			expectedType);
+      var t = tokens.shift();
+      if (t[0] == expectedType) {
+	return t;
+      } else {
+	throw new Error("Unexpected token " + t);
+      }
+    }
+
+
+
+    function readExpr() {
+      var t;
+      if (isType('(')) {
+	eat('(');
+	var result = readExprs();
+	eat(')');
+	return result;
+      } else if (isType("'")) {
+	eat("'");
+	var quoted = readExpr();
+	return plt.Kernel.cons(quoteSymbol,
+				   plt.Kernel.cons(quoted, empty));
+      } else if (isType('`')) {
+	eat("`");
+	return plt.Kernel.cons(quasiquoteSymbol,
+				   plt.kernel.cons(quoted, empty));
+      } else if (isType(',')) {
+	eat(",");
+	return plt.Kernel.cons(unquoteSymbol,
+				   plt.kernel.cons(quoted, empty));
+      } else if (isType('number')) {
+	t = eat('number');
+	if (t[1].match(/\./)) {
+	  return plt.types.FloatPoint.makeInstance(parseFloat(t[1]));
+	} else {
+	  return plt.types.Rational.makeInstance(parseInt(t[1]), 1);
+	}
+      } else if (isType('string')) {
+	t = eat('string');
+	return plt.types.String.makeInstance(t[1]);
+      } else if (isType('char')) {
+        t = eat('char');
+	  if (t[1] == 'newline') {
+	      return plt.types.Char.makeInstance('\n');
+	  }
+          else {
+	      return plt.types.Char.makeInstance(t[1]);
+	  }
+      } else if (isType('symbol')) {
+	t = eat('symbol');
+	return plt.types.Symbol.makeInstance(t[1]);
+      } else {
+	throw new Error("Parse broke with token stream " + tokens);
+      }
+    }
+
+
+    function readExprs() {
+      var result = plt.types.Empty.EMPTY;
+      while (true) {
+	if (tokens.length == 0 || isType(')')) {
+	  break;
+	} else {
+	  var nextElt = readExpr();
+	  result = plt.types.Cons.makeInstance(nextElt, result);
+	}
+      }
+      return plt.Kernel.reverse(result);
+    }
+    
+
+
+    return readExprs();
+  }
+  
+}());