private Val atom() {
Token t = lex.nextToken();
if (t.type == Token.Type.number) {
return new Num((Double) t.value);
} else if (t.type == Token.Type.string) {
return new Str("" + t.value);
} else if (t.type == Token.Type.id) {
Val res = env.val(t.value.toString());
if (res.getType() == Val.Type.nil) {
res = new Id("" + t.value);
Val expr = expr();
env.set(t.value.toString(), expr);
}
return res;
} else if (t.matchOperator("(")) {
Val v = expr();
t = lex.nextToken();
if (!t.matchOperator(")")) {
throw new EvalException("lexical error: ) was expected");
}
return v;
} else {
lex.returnToken();
return Nil.NIL;
}
}
private Val moreFactors(Val val) {
Token t = lex.nextToken();
if (t.matchOperator("*")) {
return new Num(val.evalNum(env) * levelFactor().evalNum(env));
} else if (t.matchOperator("/")) {
return new Num(val.evalNum(env) / levelFactor().evalNum(env));
} else if (t.matchOperator("%")) {
return new Num(val.evalNum(env) % levelFactor().evalNum(env));
} else {
lex.returnToken();
return val;
}
}
private Val moreTerms(Val val) {
Token t = lex.nextToken();
if (t.matchOperator("+")) {
Val rVal = levelFactor();
Val eval;
if (val.getType() == Val.Type.string) {
eval = new Str(val.evalStr(env) + rVal.evalStr(env));
} else {
eval = new Num(val.evalNum(env) + rVal.evalNum(env));
}
return moreTerms(eval);
} else if (t.matchOperator("-")) {
Val rVal = levelFactor();
Val eval = new Num(val.evalNum(env) - rVal.evalNum(env));
return moreTerms(eval);
} else {
lex.returnToken();
return val;
}
}
private Val moreCond(Val val) {
Token t = lex.nextToken();
if (t.matchOperator("?")) {
Val trueNode = expr();
Token delim = lex.nextToken();
if (delim.matchOperator("!")) {
Val falseNode = expr();
if (val.evalNum(env) > 0) {
return trueNode;
} else {
return falseNode;
}
} else {
throw new EvalException("Unrecognized ternary operation " + lex.getLastLine());
}
} else {
lex.returnToken();
return val;
}
}
private Val moreComp(Val val) {
Token t = lex.nextToken();
if (t.matchOperator("<")) {
Val rVal = moreComp(levelTerm());
return val.evalNum(env) < rVal.evalNum(env) ? new Num(1d) : new Num(0d);
} else if (t.matchOperator(">")) {
Val rVal = moreComp(levelTerm());
return val.evalNum(env) > rVal.evalNum(env) ? new Num(1d) : new Num(0d);
} else if (t.matchOperator(">=")) {
Val rVal = moreComp(levelTerm());
return val.evalNum(env) >= rVal.evalNum(env) ? new Num(1d) : new Num(0d);
} else if (t.matchOperator("<=")) {
Val rVal = moreComp(levelTerm());
return val.evalNum(env) <= rVal.evalNum(env) ? new Num(1d) : new Num(0d);
} else if (t.matchOperator("=")) {
Val rVal = moreComp(levelTerm());
return val.evalNum(env).equals(rVal.evalNum(env)) ? new Num(1d) : new Num(0d);
} else if (t.matchOperator("<>")) {
Val rVal = moreComp(levelTerm());
return !val.evalNum(env).equals(rVal.evalNum(env)) ? new Num(1d) : new Num(0d);
} else {
lex.returnToken();
return val;
}
}