public void CheckSyntax(string s) {
_tokenizer = new ExpressionTokenizer();
_evalMode = EvalMode.ParseOnly;
_tokenizer.InitTokenizer(s);
ParseExpression();
if (_tokenizer.CurrentToken != ExpressionTokenizer.TokenType.EOF) {
throw BuildParseError("Unexpected token at the end of expression", _tokenizer.CurrentPosition);
}
}
public object Evaluate(string s) {
_tokenizer = new ExpressionTokenizer();
_evalMode = EvalMode.Evaluate;
_tokenizer.InitTokenizer(s);
object val = ParseExpression();
if (_tokenizer.CurrentToken != ExpressionTokenizer.TokenType.EOF) {
throw BuildParseError("Unexpected token at the end of expression", _tokenizer.CurrentPosition);
}
return val;
}
public object Evaluate(ExpressionTokenizer tokenizer)
{
_evalMode = EvalMode.Evaluate;
_tokenizer = tokenizer;
return ParseExpression();
}
private object ParseConditional()
{
// we're on "if" token - skip it
_tokenizer.GetNextToken();
if (_tokenizer.CurrentToken != ExpressionTokenizer.TokenType.LeftParen) {
throw BuildParseError("'(' expected.", _tokenizer.CurrentPosition);
}
_tokenizer.GetNextToken();
ExpressionTokenizer.Position p0 = _tokenizer.CurrentPosition;
object val = ParseExpression();
ExpressionTokenizer.Position p1 = _tokenizer.CurrentPosition;
bool cond = false;
if (!SyntaxCheckOnly()) {
cond = (bool) SafeConvert(typeof(bool), val, "the conditional expression", p0, p1);
}
// skip comma between condition value and then
if (_tokenizer.CurrentToken != ExpressionTokenizer.TokenType.Comma) {
throw BuildParseError("',' expected.", _tokenizer.CurrentPosition);
}
_tokenizer.GetNextToken();
EvalMode oldEvalMode = _evalMode;
try {
if (!cond) {
// evaluate 'then' clause without executing functions
_evalMode = EvalMode.ParseOnly;
} else {
_evalMode = oldEvalMode;
}
object thenValue = ParseExpression();
_evalMode = oldEvalMode;
if (_tokenizer.CurrentToken != ExpressionTokenizer.TokenType.Comma) {
throw BuildParseError("',' expected.", _tokenizer.CurrentPosition);
}
_tokenizer.GetNextToken(); // skip comma
if (cond) {
// evaluate 'else' clause without executing functions
_evalMode = EvalMode.ParseOnly;
} else {
_evalMode = oldEvalMode;
}
object elseValue = ParseExpression();
_evalMode = oldEvalMode;
// skip closing ')'
if (_tokenizer.CurrentToken != ExpressionTokenizer.TokenType.RightParen) {
throw BuildParseError("')' expected.", _tokenizer.CurrentPosition);
}
_tokenizer.GetNextToken();
return cond ? thenValue : elseValue;
}
finally {
// restore evaluation mode - even on exceptions
_evalMode = oldEvalMode;
}
}
private object ParseBooleanOr()
{
ExpressionTokenizer.Position p0 = _tokenizer.CurrentPosition;
object o = ParseBooleanAnd();
EvalMode oldEvalMode = _evalMode;
try {
while (_tokenizer.IsKeyword("or")) {
bool v1 = true;
if (!SyntaxCheckOnly()) {
v1 = (bool)SafeConvert(typeof(bool), o, "the left hand side of the 'or' operator", p0, _tokenizer.CurrentPosition);
if (v1) {
// we're lazy - don't evaluate anything from now, we know that the result is 'true'
_evalMode = EvalMode.ParseOnly;
}
}
_tokenizer.GetNextToken();
ExpressionTokenizer.Position p2 = _tokenizer.CurrentPosition;
object o2 = ParseBooleanAnd();
ExpressionTokenizer.Position p3 = _tokenizer.CurrentPosition;
if (!SyntaxCheckOnly()) {
bool v2 = (bool)SafeConvert(typeof(bool), o2, "the right hand side of the 'or' operator", p2, p3);
o = v1 || v2;
}
}
return o;
} finally {
_evalMode = oldEvalMode;
}
}
static void command_mode(string[] args) => EvalMode = (EvalMode)char.Parse(args[0]);