public static VerifiedExpression Parse(string expr, CalcEnvironment env)
{
if (env == null)
{
throw new ArgumentNullException(nameof(env));
}
var tokenExpr = TokenExpression.Parse(expr);
if (tokenExpr.Success)
{
return(Verifier.VerifyExpression(tokenExpr.BackingArray, env));
}
else
{
return(new VerifiedExpression(tokenExpr.ErrorMessage, tokenExpr.ErrorPosition));
}
}
public static VerifiedExpression Create(TokenExpression tokenExpr, CalcEnvironment env)
{
if (tokenExpr == null)
{
throw new ArgumentNullException(nameof(tokenExpr));
}
if (!tokenExpr.Success)
{
throw new ArgumentException("Expression must be successfully parsed.", nameof(tokenExpr));
}
if (env == null)
{
throw new ArgumentNullException(nameof(env));
}
var arr = tokenExpr.Expression.ToArray();
return(Verifier.VerifyExpression(arr, env));
}
public static VerifiedExpression VerifyExpression(CalcToken[] tokens, CalcEnvironment env)
{
int currentDepth = 0;
// Depth/subexpression -> Argument counter & function metadata.
// A stack based solution might be better?
var funcTracking = new Dictionary <int, FunctionMetadata>();
for (int i = 0; i < tokens.Length; i++)
{
var token = tokens[i];
// Used as `out` argument in processing types ArgSeperator and ParenClose.
// The compiler complains if we define it in both cases, which are counted as the same scope.
FunctionMetadata funcMeta;
switch (token.Type)
{
// --- Verify symbol (variables and constants) ---
case TokenType.Symbol:
double numVal;
if (env.VarOrConst(token.Value, out numVal))
{
// Resolve symbol to value.
var symbol = (CalcSymbolToken)token;
tokens[i] = symbol.New(numVal);
break;
}
else
{
return(new VerifiedExpression("Undefined symbol: " + token.Value,
token.OriginIndex));
}
// --- Verify function symbol ---
case TokenType.Function:
CalcFunction func;
if (env.Function(token.Value, out func))
{
// Resolve function symbol to function.
var funcToken = (CalcFuncToken)token;
tokens[i] = funcToken.New(func);
// Record that the next subexpression (delimited by parentheses) is associated
// with a function.
funcTracking[currentDepth + 1] = new FunctionMetadata(func, funcToken);
break;
}
else
{
return(new VerifiedExpression("Undefined function symbol: " + token.Value,
token.OriginIndex));
}
// --- Keep count of arguments to functions ---
case TokenType.ArgSeperator:
if (funcTracking.TryGetValue(currentDepth, out funcMeta))
{
// Another seperator, another function argument.
// The previous stage assures that there will be an operand.
funcMeta.ArgCounter++;
}
break;
// --- Record opening and closing of parentheses ---
case TokenType.ParenOpen:
currentDepth++;
break;
case TokenType.ParenClose:
// If the subexpression we're closing/leaving is associated with a function we need to
// verify the function argument count.
if (funcTracking.TryGetValue(currentDepth, out funcMeta))
{
if (!funcMeta.CountsAreEqual)
{
// And this is why we kept around that metadata, so we could report the appropriate
// information on encountering an discrepancy in argument count.
return(new VerifiedExpression(
string.Format("Invalid number of arguments for {0} (got {1} expected {2})",
funcMeta.FuncSymbol, funcMeta.ArgCounter, funcMeta.RequiredArgs),
funcMeta.OriginIndex));
}
// We're leaving the current depth, we no longer need this information.
funcTracking.Remove(currentDepth);
}
currentDepth--;
break;
// --- The rest is not important for this stage ---
default:
continue;
} // switch
} // for
// We have successfully stepped through the expression without encountering undefined symbols or functions
// and the functions were supplied the correct number of arguments. Hurray!
return(new VerifiedExpression(tokens));
}