<YYINITIAL> param { return tok(Sym.PARAM, yytext()); }
<YYINITIAL> "=>" { return tok(Sym.IMPLIES, yytext()); }
<YYINITIAL> true { return tok(Sym.TRUE, yytext()); }
+<YYINITIAL> false { return tok(Sym.FALSE, yytext()); }
<YYINITIAL> isvalid { return tok(Sym.ISVALID, yytext()); }
<YYINITIAL> for { return tok(Sym.FOR, yytext()); }
<YYINITIAL> to { return tok(Sym.TO, yytext()); }