internal override Value Copy()
{
var res = new SExprValue();
foreach (var c in Cell)
{
res.Cell.Add(c.Copy());
}
return(res);
}
/// <summary>
/// Creates an S-Expr from the Q-Expr
/// </summary>
/// <returns>The SE xpression.</returns>
internal SExprValue CreateSExpression()
{
var res = new SExprValue();
foreach (var c in Cell)
{
res.Cell.Add(c.Copy());
}
return(res);
}
/// <summary>
/// Consumes an ASTNode + Child elements to produce a JListValue node + Child elements.
/// </summary>
/// <returns>The ASTN ode.</returns>
/// <param name="astNode">Ast node.</param>
internal static Value FromASTNode(AbstractSyntaxNode astNode)
{
AbstractSyntaxTerminalNode terminalNode = astNode.As <AbstractSyntaxTerminalNode>();
AbstractSyntaxRuleNode ruleNode = astNode.As <AbstractSyntaxRuleNode>();
if (terminalNode != null)
{
if (terminalNode.TerminalSymbol.Name.Equals("NUMBER", StringComparison.Ordinal))
{
long l;
if (long.TryParse(terminalNode.Value, out l))
{
return(new LongValue(l));
}
else
{
return(new ErrorValue($"Invalid number '{terminalNode.Value}'."));
}
}
else if (terminalNode.TerminalSymbol.Name.Equals("SYMBOL", StringComparison.Ordinal))
{
return(new SymbolValue(terminalNode.Value));
}
else if (terminalNode.TerminalSymbol.Name.Equals("STRING", StringComparison.Ordinal))
{
return(StringValue.ReadRegexString(terminalNode.Value));
}
else if (terminalNode.TerminalSymbol.Name.Equals("COMMENT", StringComparison.Ordinal))
{
return(new SExprValue());
}
}
else if (ruleNode != null)
{
if (new string[] { "JLisp", "SExpr" }.Contains(ruleNode.ProductionRule.Name))
{
var s = new SExprValue();
BuildJLispExprValueChildren(ruleNode, s.Cell);
return(s);
}
else if (ruleNode.ProductionRule.Name.Equals("QExpr", StringComparison.Ordinal))
{
var q = new QExprValue();
BuildJLispExprValueChildren(ruleNode, q.Cell);
return(q);
}
else if (ruleNode.ProductionRule.Name.Equals("Expr", StringComparison.Ordinal))
{
return(FromASTNode(ruleNode.Children[0])); // Should only be one !!
}
}
return(new ErrorValue("No handling for astNode: " + astNode));
}
static Value EvalSexpr(Env environment, SExprValue sexpr)
{
// Evaluate Children
for (int i = 0; i < sexpr.Cell.Count; i++)
{
sexpr.Cell[i] = Eval(environment, sexpr.Cell[i]);
}
// Check for errors - and return the first encountered
var errored = sexpr.Cell.Where(c => c is ErrorValue).FirstOrDefault();
if (errored != null)
{
return(errored);
}
// Empty Expression
if (sexpr.Cell.Count == 0)
{
return(sexpr);
}
// Single Expression
if (sexpr.Cell.Count == 1)
{
return(sexpr.Cell[0]);
}
// Ensure first element is a function after evaluation
Value first = sexpr.Cell[0];
sexpr.Cell.RemoveAt(0);
if (!(first is FuncValue))
{
return(new ErrorValue($"s-expr Does not start with a function. Encountered '{first.Type}'."));
}
// Call the function
return(Call(environment, first.As <FuncValue>(), sexpr));
}
internal static Value Call(Env environment, FuncValue function, SExprValue arguments)
{
BuiltinFuncValue builtin = function.As <BuiltinFuncValue>();
LambdaFuncValue lambda = function.As <LambdaFuncValue>();
// If Builtin then simply call that
if (builtin != null)
{
return(builtin.BuiltinFunction(environment, arguments));
}
// Record Argument Counts
int given = arguments.Cell.Count;
int total = lambda.Formals.Cell.Count;
// While arguments still remain to be processed
while (arguments.Cell.Count > 0)
{
// If we've ran out of formal arguments to bind
if (lambda.Formals.Cell.Count == 0)
{
return(new ErrorValue($"Function passed too many arguments. Got {given}, Expected {total}."));
}
// Pop the first symbol from the formals
SymbolValue symbol = lambda.Formals.Cell[0].As <SymbolValue>();
lambda.Formals.Cell.RemoveAt(0);
// Special Case to deal with '&'
if (symbol.Value == "&")
{
// Ensure '&' is followed by another symbol
if (lambda.Formals.Cell.Count != 1)
{
return(new ErrorValue("Function format invalid. Symbol '&' not followed by single symbol."));
}
// Next formal should be bound to remaining arguments.
SymbolValue nsym = lambda.Formals.Cell[0].As <SymbolValue>();
lambda.Formals.Cell.RemoveAt(0);
lambda.Environment.Put(nsym.Value, Builtins.List(environment, arguments));
break;
}
// Pop the next argument from the list
Value val = arguments.Cell[0];
arguments.Cell.RemoveAt(0);
// Bind a copy into the function's environment
lambda.Environment.Put(symbol.Value, val);
}
// Argument list is now bound.
// if '&' remains in formal list after we've bound arguments then bind to empty list
if (lambda.Formals.Cell.Count > 0 &&
lambda.Formals.Cell[0].As <SymbolValue>().Value == "&")
{
// check to ensure that & is not passed invalidly.
if (lambda.Formals.Cell.Count != 2)
{
return(new ErrorValue("Function format invalid. Symbol '&' not followed by single symbol."));
}
// Pop and throw away '&' symbol
lambda.Formals.Cell.RemoveAt(0);
// Pop next symbol and create empty list
SymbolValue symbolValue = lambda.Formals.Cell[0].As <SymbolValue>();
lambda.Formals.Cell.RemoveAt(0);
QExprValue val = new QExprValue();
// Bind to environment and delete
lambda.Environment.Put(symbolValue.Value, val);
}
// If all formals have been bound evaluate
if (lambda.Formals.Cell.Count == 0)
{
// Set environment parent to evaluation environment
lambda.Environment.Parent = environment;
// Evaluate and return
var sexpr = new SExprValue();
sexpr.Cell.Add(lambda.Body.Copy());
return(Builtins.Eval(lambda.Environment, sexpr));
}
else
{
// Otherwise return partially evaluated function
return(lambda.Copy());
}
}
