XML — Architecture, Tools, Techniques - Department of Computer ...

** lexical analyzer for arithmetic expressions.
*/
public class Scanner implements oops.parser.Scanner {
protected StreamTokenizer st; // to read input
protected Parser parser; // to get Lit/Token tokenSet values
protected Set NUMBER; // tokenSet for Number
protected Set tokenSet; // null or lookahead identifying token
protected Object node; // Double/Long value for Number
public Set tokenSet () { return tokenSet; }
public Object node () { return node; }
public String toString () { return st.toString(); }
}
public void scan (Reader r, Parser parser) throws IOException {
st = new StreamTokenizer(new FilterReader(new BufferedReader(r)) {
boolean addSpace; // kludge to duplicate \n
public int read () throws IOException {
int ch = '\n';
addSpace = addSpace ? false : (ch = in.read()) == '\n';
return ch;
}
});
st.resetSyntax();
st.commentChar('#'); // comments from # to end-of-line
st.wordChars('0', '9'); // parse decimal numbers as words
st.wordChars('.', '.');
st.whitespaceChars(0, ' '); // ignore control-* and space
st.eolIsSignificant(true); // need '\n'
this.parser = parser;
NUMBER = ((Token)parser.getPeer("Number")).getLookahead();
advance(); // one token lookahead
}
public boolean atEnd () { return st.ttype == st.TT_EOF; }
40
oops/Scanner.java
public boolean advance () throws IOException {
if (atEnd()) return false;
switch (st.nextToken()) {
case StreamTokenizer.TT_EOF: node = null; tokenSet = null; return false;
case StreamTokenizer.TT_EOL: node = null; tokenSet = parser.getLitSet("\n");
break;
case StreamTokenizer.TT_WORD: node = st.sval.indexOf(".") < 0
? (Number)new Long(st.sval)
: (Number)new Double(st.sval);
tokenSet = NUMBER;
break;
default: node = ""+(char)st.ttype;
tokenSet = parser.getLitSet((String)node);
break;
}
return true;
}