public SScope SpawnScopeWith(string[] names, SObject[] values)
{
if (names.Length < values.Length)
{
throw new Exception("too many arguments");
}
var scope = new SScope(this);
for (int i = 0; i < names.Length; ++i)
{
scope._symbolTable.Add(names[i], values[i]);
}
return(scope);
}
public static void KeepInterpretingInConsole(this SScope scope, Func <string, SScope, SObject> evaluate)
{
while (true)
{
//try
{
Console.ForegroundColor = ConsoleColor.Gray;
Console.Write(">> ");
String code;
if (!String.IsNullOrWhiteSpace(code = Console.ReadLine()))
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine(">> " + evaluate(code, scope));
}
}
//catch (Exception ex)
//{
// Console.ForegroundColor = ConsoleColor.Red;
// Console.WriteLine(">> " + ex.Message);
//}
}
}
public static SBool ChainRelation(this SExpression[] expressions, SScope scope, Func <SNumber, SNumber, Boolean> relation)
{
if (expressions.Length <= 1)
{
throw new Exception("too few arguments.");
}
var current = expressions[0].Evaluate(scope) as SNumber;
foreach (var obj in expressions.Skip(1))
{
var next = obj.Evaluate(scope) as SNumber;
if (relation(current, next))
{
current = next;
}
else
{
return(SBool.False);
}
}
return(SBool.True);
}
public SFunction(SExpression body, string[] parameters, SScope scope)
{
Body = body;
Parameters = parameters;
Scope = scope;
}
public SObject Evaluate(SScope scope)
{
if (Children.Count == 0)
{
Int64 number;
if (Int64.TryParse(Value, out number))
{
return(number);
}
else
{
return(scope.Find(Value));
}
}
else
{
var first = Children[0].Value;
if (first == "list")
{
return(new SList(this.Children.Skip(1).Select(exp => exp.Evaluate(scope))));
}
else if (first == "if")
{
var condition = Children[1].Evaluate(scope) as SBool;
return(condition ? Children[2].Evaluate(new SScope(scope)) :Children[3].Evaluate(new SScope(scope)));
}
else if (first == "define")
{
var child = Children[1];
if (child.Value == "(")
{
var funcName = child.Children[0].Value;
var body = Children[2];
var parameters = child.Children.Skip(1).Select(exp => exp.Value).ToArray();
var newScope = new SScope(scope);
var func = new SFunction(body, parameters, newScope);
return(scope.Define(funcName, func));
}
return(scope.Define(Children[1].Value, Children[2].Evaluate(scope)));
}
else if (first == "set!")
{
var variableName = Children[1].Value;
var newValue = Children[2];
if (scope.Find(variableName) != null)
{
return(scope.Reset(variableName, newValue.Evaluate(scope)));
}
}
else if (first == "begin")
{
SObject result = null;
foreach (var statement in Children.Skip(1))
{
result = statement.Evaluate(scope);
}
return(result);
}
else if (SScope.BuiltinFunctions.ContainsKey(first))
{
var arguments = Children.Skip(1).ToArray();
return(SScope.BuiltinFunctions[first](arguments, scope));
}
else
{
var func = first == "(" ? /*High-order function*/ Children[0].Evaluate(scope) as SFunction
: scope.Find(first) as SFunction;
var arguments = Children.Skip(1).Select(s => s.Evaluate(scope)).ToArray();
return(func.Update(arguments).Evaluate());
}
}
throw new Exception("Sorry!");
}
public SScope(SScope parent)
{
Parent = parent;
_symbolTable = new Dictionary <string, SObject>();
}
public static IEnumerable <T> Evaluate <T>(this IEnumerable <SExpression> expressions, SScope scope)
where T : SObject
{
return(expressions.Evaluate(scope).Cast <T>());
}
public static IEnumerable <SObject> Evaluate(this IEnumerable <SExpression> expressions, SScope scope)
{
return(expressions.Select(exp => exp.Evaluate(scope)));
}