public object Evaluate(Environment environment, object expression) => Evaluation(environment, Syntax.Parse((string)(expression as object[])[0]), true);
protected virtual object Evaluation(Environment environment, object expression, bool topLevel)
{
var list = expression as object[];
var symbol = Syntax.Symbol(expression);
if (environment == null)
{
return(Validate().Evaluation(new Environment(this, Semantics), expression));
}
else if (list != null)
{
Keyword keyword;
if ((list.Length > 1) && ((symbol = Syntax.Symbol(list[1])) != null) && ((keyword = Keyword(symbol.Id)) != null))
{
if (keyword.IsInfix)
{
var head = Syntax.Symbol(list[0]);
var lead = head != null?Keyword(head.Id) : null;
if ((lead == null) || !IsReserved(lead))
{
return(keyword.Semantic(environment, new[] { list[0] }.Concat(list.Skip(2)).ToArray()));
}
throw Error("infix keyword {0} not allowed after reserved keyword {1}", keyword, lead);
}
throw Error("not an infix keyword at position 2: {0}", keyword);
}
if ((list.Length > 0) && ((symbol = Syntax.Symbol(list[0])) != null) && ((keyword = Keyword(symbol.Id)) != null))
{
return(keyword.Semantic(environment, list.Skip(1).ToArray()));
}
else
{
int length;
list = list.Select(item => Evaluation(environment, item)).ToArray();
if (((length = list.Length) > 0) && ((symbol = Syntax.Symbol(list[0])) != null) && (symbol is Callable))
{
var callable = (Callable)symbol;
var variadic = callable.Variadic;
var arguments = new object[variadic ? length - 1 : length];
if (length > 1)
{
Array.Copy(list, 1, arguments, variadic ? 0 : 1, length - 1);
}
if (variadic)
{
return(callable.Invoke(environment, arguments));
}
else
{
arguments[0] = environment;
return(callable.Invoke(arguments));
}
}
else
{
return(list);
}
}
}
else if (symbol != null)
{
return((Delegator != null ? Delegator(environment, symbol) : null) ?? environment.Get(symbol.Id));
}
else
{
return((Delegator != null ? Delegator(environment, expression) : null) ?? expression);
}
}
public Language(Syntax syntax)
{
Syntax = syntax ?? new Syntax();
Semantics = new Dictionary <string, object>(GetReflectedSemantics());
Reserved = new HashSet <Semantic>(new Semantic[] { Evaluation, Application, Quoting, Construction, Letting, Abstraction, Testing });
}
public override string ToString()
{
var pair = (object[])Definition; return(string.Concat(Syntax.ToString(pair[0]), " => ", Syntax.ToString(pair[1])));
}
