new built-in variables for each type

examples/json/json.noja

@@ -0,0 +1,171 @@
+
+fun isSpace(c)
+    return c == " " or c == "\t" or c == "\n";
+
+fun isDigit(c) {
+    u = unicode(c);
+    d = u - unicode("0");
+    return d >= 0 and d <= 9;
+}
+
+fun skipSpaces(context) {
+    # Skip zero or more whitespace characters.
+    while context.cur < count(context.str) 
+      and isSpace(context.str[context.cur]):
+      context.cur = context.cur + 1;
+}
+
+fun parseNull(context) {
+    
+    assert(context.cur < count(context) 
+       and context.str[context.cur] == 'n');
+    
+    if context.cur+3 > count(context)
+    or context.str[context.cur+1] != 'u' 
+    or context.str[context.cur+2] != 'l'
+    or context.str[context.cur+3] != 'l':
+        return none, "Unexpected token starting with \"n\"";
+    
+    context.cur = context.cur + count("null");
+    return none;
+}
+
+fun parseTrue(context) {
+    
+    assert(context.cur < count(context) 
+       and context.str[context.cur] == 't');
+    
+    if context.cur+3 > count(context)
+    or context.str[context.cur+1] != 'r' 
+    or context.str[context.cur+2] != 'u'
+    or context.str[context.cur+3] != 'e':
+        return none, "Unexpected token starting with \"t\"";
+    
+    context.cur = context.cur + count("true");
+    return true;
+}
+
+fun parseFalse(context) {
+    
+    assert(context.cur < count(context) 
+       and context.str[context.cur] == 'f');
+    
+    if context.cur+3 > count(context)
+    or context.str[context.cur+1] != 'a' 
+    or context.str[context.cur+2] != 'l'
+    or context.str[context.cur+3] != 's'
+    or context.str[context.cur+4] != 'e':
+        return none, "Unexpected token starting with \"f\"";
+    
+    context.cur = context.cur + count("false");
+    return false;
+}
+
+fun skip(context, test_callback) {
+    k = context.cur;
+    while k < count(context) and test_callback(context.str[k]):
+        k = k + 1;
+    return k;
+}
+
+fun parseInteger(context) {
+    assert(context.cur < count(context) and isDigit(context.str[context.cur]));
+
+    buffer = 0;
+
+    do {
+        c = context.str[context.cur];
+        d = unicode(c) - unicode('0');
+        buffer = buffer * 10 + d;
+        context.cur = context.cur + 1;
+    } while context.cur < count(context) 
+        and isDigit(context.str[context.cur]);
+    
+    return buffer;
+}
+
+fun parseFloating(context) {
+    assert(context.cur < count(context) and isDigit(context.str[context.cur]));
+
+    # It's ensured by the caller (parseIntegerOrFloating)
+    # that now the strings contains two sequences of
+    # digits with a dot in the middle.
+
+    buffer = 0.0;
+
+    # Scan the integer part.
+    do {
+        c = context.str[context.cur];
+        d = unicode(c) - unicode('0');
+        buffer = buffer * 10 + d;
+        context.cur = context.cur + 1;
+    } while context.str[context.cur] != ".";
+    
+    assert(isDigit(context.str[context.cur+1]));
+
+    # Scan the decimal part.
+    q = 1;
+    do {
+        c = context.str[context.cur];
+        d = unicode(c) - unicode('0');
+        q = q / 10;
+        buffer = buffer + q * d;
+        context.cur = context.cur + 1;
+    } while context.cur < count(context)
+        and isDigit(context);
+
+    return buffer;
+}
+
+fun parseIntegerOrFloating(context) {
+    assert(context.cur < count(context) and isDigit(context.str[context.cur]));
+
+    # Is the first digit sequence followed by a dot
+    # and then one or more digits?
+
+    k = skip(context, isDigit);
+    if k+1 < count(context) and context.str[k] == "." and isDigit(context.str[k+1]):
+        # It's a floating point value, then!
+        return parseFloating(context);
+    else
+        # It's good old integer!
+        return parseInteger(context);
+}
+
+fun parseValue(context) {
+
+    if context.cur == count(context):
+        return none, "Source ended where a value was expected";
+
+    c = context.str[context.cur];
+    if c == "{":
+        val, err = parseObject(context);
+    else if c == "[":
+        val, err = parseArray(context);
+    else if c == '"':
+        val, err = parseString(context);
+    else if isDigit(c):
+        val, err = parseIntegerOrFloating(context);
+    else if c == 'n':
+        val, err = parseNull(context);
+    else if c == 't': 
+        val, err = parseTrue(context);
+    else if c == 'f':
+        val, err = parseFalse(context);
+    else {
+        val = none;
+        err = strcat("Unexepected character \"", c, "\" where a value was expected");
+    }
+    return val, err;
+}
+
+fun parse(str) {
+    context = {str: str, cur: 0};
+    skipSpaces(context);
+    val, err = parseValue(context);
+    return val, err;
+}
+
+val, err = parse('3.14');
+print("val=[", val, "]\n");
+print("err=[", err, "]\n");