public static EvalResult evaluate_System_Function(SymbolTable symbols, FunCall fun_call)
{
var fun_name = fun_call.value.value;
EvalFunc f = (s,func) => new EvalResult(new Error(fun_call.value.line_num, "Could not match system function!"));
switch (fun_name)
{
case "define": f = add_definition; break;
case "+": f = addition; break;
case "-": f = subtraction; break;
case "*": f = multiplication; break;
case "/": f = division; break;
case "%": f = mod; break;
case "head": f = head; break;
case "tail": f = tail; break;
case "++": f = cons; break;
case "==": f = equality_test; break;
case "not": f = not; break;
case "&&": f = logical_and; break;
case "||": f = logical_or; break;
case "<": f = less_than; break;
case ">": f = greater_than; break;
}
return f(symbols, fun_call);
}
private static EvalResult gen_function_call_error(FunCall source, int definition_arg_count)
{
string fun_name = source.value.value;
string prefix = (source.args.Count > definition_arg_count) ? "To many " : "To few";
string error_message = prefix + "arguements to " + fun_name + " it takes " + definition_arg_count.ToString();
return new EvalResult(new Error(source.value.line_num, fun_name, error_message));
}
public static EvalResult evaluate_Identity(SymbolTable symbols, FunCall val)
{
// Evaluate symbol
if (val.value != null && val.value.type == Lexical.Symbol && symbols.ContainsKey(val.value.value))
{
return evaluate_Identity(symbols, symbols[val.value.value]);
}
else return new EvalResult(new EvalT(symbols, val));
}
public static EvalResult cons(SymbolTable symbols, FunCall list)
{
return eval_args(symbols, list, "cons", 2, (s, func) =>
{
var element = func.args[0];
var list_arg = func.args[1];
return new EvalResult(new EvalT(symbols, FunCall.id_list(new List<FunCall> { element, list_arg })));
});
}
public static EvalResult add_definition(SymbolTable symbols, FunCall val)
{
var new_fun_name = val.args[0].args.First().value.value;
var parameters = FunCall.id_list(val.args[0].flattened_args().Skip(1).ToList());
var fun_body = val.args[1];
symbols.Add(new_fun_name, FunCall.id_list(new List<FunCall> { parameters, fun_body }));
return new EvalResult(new EvalT(symbols, new FunCall(Token.symbol("Function Defined"))));
}
public static EvalResult not(SymbolTable symbols, FunCall funcall)
{
return eval_args(symbols, funcall, "not", 1, (s, func) =>
{
var result = func.args[0].value;
if (result.type != Lexical.Bool) return new EvalResult(new Error(0, "not needs a bool argument!"));
else if (result.value == "true") return new EvalResult(new EvalT(symbols, FunCall.id_val(Lexical.Bool, 0, "false")));
else return new EvalResult(new EvalT(symbols, FunCall.id_val(Lexical.Bool, 0, "true")));
});
}
public static EvalResult binary_typeCheck(SymbolTable symbols, FunCall funcall, string funcName, EvalFunc f)
{
var left = funcall.args[0].value;
var right = funcall.args[1].value;
Func<Token, bool> isNumber = token => token.type == Lexical.Int || token.type == Lexical.Float;
bool areNumbers = isNumber(left) && isNumber(right);
if (areNumbers || left.type == right.type) return f(symbols, funcall);
else return new EvalResult(new Error(0, "Non-matching types for " + funcName));
}
public static EvalResult list_access(SymbolTable symbols, FunCall list, Func<SymbolTable, FunCall, EvalResult> list_op, string func_name)
{
return eval_args(symbols, list, func_name, 2, (s, func) =>
{
var list_arg = func.args.First();
if (!isList(list_arg)) return new EvalResult(new Error(0, func_name + " must be called on a list!"));
return list_op(symbols, list_arg);
});
}
public static EvalResult less_than(SymbolTable symbols, FunCall funcall)
{
return eval_args(symbols, funcall, "<", 2, (_s, _func) =>
{
return binary_typeCheck(symbols, funcall, "<", (s, func) =>
{
var left = Convert.ToDouble(func.args[0].value.value);
var right = Convert.ToDouble(func.args[1].value.value);
var result = (left < right).ToString();
return new EvalResult(new EvalT(s, FunCall.id_val(Lexical.Bool, 0, result)));
});
});
}
public static EvalResult logical_or(SymbolTable symbols, FunCall funcall)
{
return eval_args(symbols, funcall, "||", 2, (_s, _func) =>
{
return binary_typeCheck(_s, _func, Lexical.Bool, Lexical.Bool, "||", (s, func) =>
{
var left = func.args[0].value;
var right = func.args[1].value;
string result = "";
if (left.value == "true" || right.value == "true") result = "true";
else result = "false";
return new EvalResult(new EvalT(s, FunCall.id_val(Lexical.Bool, 0, result)));
});
});
}
public static EvalResult math_op(SymbolTable symbols, FunCall fun, Func<Token, double, double> math_op, string func_name)
{
var args = fun.args.Select(a => evaluate_FunCall(symbols, a));
Func<FunCall, bool> isNumerical = arg => arg.value.type == Lexical.Int || arg.value.type == Lexical.Float;
double sum = 0;
bool seen_first_val = false;
foreach (var arg in fun.args)
{
FunCall val = arg;
if (!isNumerical(val) && symbols.ContainsKey(arg.value.value))
val = symbols[arg.value.value];
if (isNumerical(val))
{
if (!seen_first_val)
{
sum = math_identity(val.value);
seen_first_val = true;
}
else sum = math_op(val.value, sum);
}
else
{
string prefix = (val.value.type == Lexical.Symbol) ? "Undefined Symbol" : "Non-numerical value ";
string message = prefix + val.ToString() + " given to " + func_name;
var error = new Error(fun.value.line_num, val.ToString(), message);
return new EvalResult(error);
}
}
var isInt = Regex.IsMatch(sum.ToString(), @".*\.0+");
Token result = isInt ? new Token(Lexical.Int, 0, ((int)sum).ToString()) : new Token(Lexical.Float, 0, sum.ToString());
return new EvalResult(new EvalT(symbols, new FunCall(result)));
}
public static EvalResult subtraction(SymbolTable symbols, FunCall fun)
{
return math_op(symbols, fun, perform_subtraction, "-");
}
public static EvalResult evaluate_FunCall(SymbolTable symbols, FunCall fun)
{
bool function = fun.value != null && fun.value.type == Lexical.Symbol;
if (function) return evaluate_Function(symbols, fun);
else return evaluate_Identity(symbols, fun);
}
public static EvalResult evaluate_Function(SymbolTable symbols, FunCall fun_call)
{
var fun_name = fun_call.value.value;
if (reserved_symbols.Contains(fun_name)) return evaluate_System_Function(symbols, fun_call);
else if (symbols.ContainsKey(fun_name)) return evaluate_User_Function(symbols, fun_call);
return null;
}
public static EvalResult evaluate_User_Function(SymbolTable symbols, FunCall fun_call)
{
FunCall definition = symbols[fun_call.value.value];
FunCall funArgs = definition.args[0];
FunCall funBody = definition.args[1];
if (fun_call.args.Count != funArgs.args.Count)
return gen_function_call_error(fun_call, funArgs.args.Count);
var arg_pairs = funArgs.args.Zip(fun_call.args, (a, b) => new Tuple<FunCall, FunCall>(a, b));
// Bind args and add to symbol table
foreach (var arg_pair in arg_pairs) symbols.Add(arg_pair.Item1.value.value, arg_pair.Item2);
return evaluate_FunCall(symbols, funBody);
}
public static EvalResult eval_args(SymbolTable symbols, FunCall funcall, string funcName, int numArgs, EvalFunc f)
{
var evaled_args = funcall.args.Select(i => evaluate_FunCall(symbols, i)).ToList();
if (evaled_args.Count() > numArgs) return new EvalResult(new Error(0, "Too many arguments to " + funcName + "!"));
if (evaled_args.Count() < numArgs) return new EvalResult(new Error(0, "Too few arguments to " + funcName + "!"));
foreach(var result in evaled_args)
if (result.left == null) return new EvalResult(result.right);
var results = FunCall.id_list(evaled_args.Select(a => a.left.Item2).ToList());
return f(symbols, results);
}
public static List<FunCall> id(FunCall value)
{
return new List<FunCall> { value };
}
public static EvalResult mod(SymbolTable symbols, FunCall fun)
{
return math_op(symbols, fun, perform_mod, "%");
}
public static EvalResult get_head(SymbolTable symbols, FunCall result_list)
{
return new EvalResult(new EvalT(symbols, result_list.args_head()));
}
public static EvalResult division(SymbolTable symbols, FunCall fun)
{
return math_op(symbols, fun, perform_division, "/");
}
public static EvalResult head(SymbolTable symbols, FunCall list)
{
return list_access(symbols, list, get_head, "head");
}
public static bool isList(FunCall list)
{
return list.value == null;
}
public static EvalResult equality_test(SymbolTable symbols, FunCall funcall)
{
return eval_args(symbols, funcall, "==", 2, (s, func) =>
{
var left = func.args[0];
var right = func.args[1];
string result = "";
switch (left.value.type)
{
case Lexical.Bool: result = (left.value.value == right.value.value).ToString(); break;
case Lexical.Int:
case Lexical.Float: result = (Convert.ToDouble(left.value.value) == Convert.ToDouble(right.value.value)).ToString(); break;
case Lexical.String: result = (left.value.value == right.value.value).ToString(); break;
default: return new EvalResult(new Error(0, "Unknown lex type passed to equality_test"));
}
return new EvalResult(new EvalT(symbols, FunCall.id_val(Lexical.Bool, 0, result)));
});
}
public static EvalResult tail(SymbolTable symbols, FunCall list)
{
return list_access(symbols, list, get_tail, "tail");
}
public static EvalResult multiplication(SymbolTable symbols, FunCall fun)
{
return math_op(symbols, fun, perform_multiplication, "*");
}
public static EvalResult get_tail(SymbolTable symbols, FunCall result_list)
{
var new_list = FunCall.id_list(result_list.args_tail());
return new EvalResult(new EvalT(symbols, new_list));
}
public static EvalResult addition(SymbolTable symbols, FunCall fun)
{
return math_op(symbols, fun, perform_additon, "+");
}