public bool TryGetVariable(String key, out Sexp s)
{
bool found = _variables.TryGetValue(key, out s);
if (!found)
{
if (_parent != null)
{
return(_parent.TryGetVariable(key, out s));
}
}
return(found);
}
public Sexp Call(ref Environment e, MemoryStream ms, Sexp sexp)
{
if (sexp.Length == _parameterNames.Count)
{
int i = 0;
Environment eClone = new Environment(e);
// add the respective sexps to the parameter names
foreach (String s in _parameterNames)
{
eClone.SetVariable(s, Evaluator.Evaluate(ref eClone, ms, sexp[i]));
++i;
}
// only return the last value so default to Void
Sexp outSexp = Sexp.Void;
foreach (Sexp s in Body)
{
outSexp = Evaluator.Evaluate(ref eClone, ms, s);
}
return(outSexp);
}
throw new CrispArgumentException(String.Format("'{0}' function expects {1} arguments, got {1}", _name, _parameterNames.Count, sexp.Length), sexp.Line);
}
/// <summary>
/// Evaluates an Sexp using a provided environment returning it's value
/// </summary>
/// <param name="e">Supplied environment</param>
/// <param name="ms">Stream that functions can output to</param>
/// <param name="sexp">Sexp to be evaluated</param>
/// <returns>Sexp</returns>
public static Sexp Evaluate(ref Environment e, MemoryStream ms, Sexp sexp)
{
foreach (Sexp innerSexp in sexp)
{
// lists can be evaluated if it doesn't start with a ident
if (innerSexp.Type == SexpType.LIST)
{
if (innerSexp[0].Type == SexpType.IDENT)
{
Evaluate(ref e, ms, innerSexp);
}
else
{
return(innerSexp);
}
}
else if (innerSexp.Type == SexpType.IDENT) // has to be resolved
{
// collects all sexps
List <Sexp> allSexps = new List <Sexp>(sexp);
if (allSexps.Count > 1) // has been given arguments
{
// check for builtin function, if found it executes it
Environment.CrispFunction cf;
if (e.TryGetBuiltinFunction(innerSexp.Value, out cf))
{
return(cf(ref e, ms, Sexp.FromList(allSexps.GetRange(1, allSexps.Count - 1))));
}
else
{
// check for a user defined function, if found executes it
CrispUserFunction cuf;
if (e.TryGetUserFunction(innerSexp.Value, out cuf))
{
return(cuf.Call(ref e, ms, Sexp.FromList(allSexps.GetRange(1, allSexps.Count - 1))));
}
else
{
// check for a varible, if found return it
Sexp s;
if (e.TryGetVariable(innerSexp.Value, out s))
{
return(s);
}
else
{
// not found
throw new CrispNotExistsException(String.Format("'{0}' does not exist in this namespace", innerSexp.Value), innerSexp.Line);
}
}
}
}
else // no args added
{
// check for builtin function, if found it executes it
Environment.CrispFunction cf;
if (e.TryGetBuiltinFunction(innerSexp.Value, out cf))
{
return(cf(ref e, ms, Sexp.Void));
}
else
{
// check for a user defined function, if found executes it
CrispUserFunction cuf;
if (e.TryGetUserFunction(innerSexp.Value, out cuf))
{
return(cuf.Call(ref e, ms, Sexp.Void));
}
else
{
// check for a varible, if found return it
Sexp s;
if (e.TryGetVariable(innerSexp.Value, out s))
{
return(s);
}
else
{
// not found
throw new CrispNotExistsException(String.Format("'{0}' does not exist in this namespace", innerSexp.Value), innerSexp.Line);
}
}
}
}
}
else
{
return(innerSexp);
}
}
return(Sexp.Void);
}
/// <summary>
/// This function turns a list of tokens into a list of Sexps. It recursively creates Sexps
/// of type list, every top-level function call are actually stored in an Sexp
/// </summary>
/// <param name="tokens">The list of tokens to read</param>
/// <param name="i">A shared index to keep track of next token throughout the recursive calls</param>
/// <param name="numberOfParens">A shared interger that marks how many open parenthesises</param>
/// <returns>A list of all Sexp values to be passed to the evaluator</returns>
private Sexp Parse(List <Token> tokens, ref int i, ref int numberOfParens)
{
Sexp curr = new Sexp();
for (; i < tokens.Count; ++i)
{
Token t = tokens[i];
switch (t.Type)
{
case TokenType.OPEN_PAREN:
++i; // needs to be incremented here to stop an infinite recursion error
++numberOfParens;
curr.Type = SexpType.LIST;
curr.Add(Parse(tokens, ref i, ref numberOfParens));
break;
case TokenType.CLOSE_PAREN:
--numberOfParens;
// tests if there is a surplus ')' token
if (numberOfParens < 0)
{
throw new CrispParserExpcetion("Mismatched parenthesises", t.Line);
}
return(curr);
case TokenType.INTEGER_LITERAL:
curr.Add(new Sexp(SexpType.INT, t.Value, t.Line));
break;
case TokenType.FLOAT_LITERAL:
curr.Add(new Sexp(SexpType.FLOAT, t.Value, t.Line));
break;
case TokenType.CHAR_LITERAL:
curr.Add(new Sexp(SexpType.CHAR, t.Value, t.Line));
break;
case TokenType.IDENT:
curr.Add(new Sexp(SexpType.IDENT, t.Value, t.Line));
break;
case TokenType.STRING_LITERAL:
curr.Add(new Sexp(SexpType.STRING, t.Value, t.Line));
break;
case TokenType.BOOL_LITERAL:
curr.Add(new Sexp(SexpType.BOOL, t.Value, t.Line));
break;
case TokenType.EOF:
// In a valid program there should be no unmatched '(' character
if (numberOfParens != 0)
{
throw new CrispParserExpcetion("Mismatched parenthesises", tokens[i - 1].Line);
}
break;
default:
break;
}
}
return(curr);
}
public void SetVariable(String key, Sexp value)
{
_variables[key] = value;
}