// Return the value of a target symbol in this or an outer scope.
public JKLVal Get(JKLSym keySymbol)
{
Env e = Find(keySymbol);
if (e == null)
{
switch (keySymbol.ToString(true))
{
// Some symbols are only valid when used in a particular context.
case "unquote":
throw new JKLEvalError("'unquote' used incorrectly (missing macro?)");
case "quasiquote":
throw new JKLEvalError("'quasiquote' used incorrectly (missing macro?)");
case "splice-unquote":
throw new JKLEvalError("'splice-unquote' used incorrectly (missing macro?)");
}
//// If here the symbol simply hasn't been defined or is mis-spelt.
throw new JKLLookupError("Get - Symbol not found '" + keySymbol.ToString(true) + "'");
}
else
{
if (e.data.TryGetValue(keySymbol.getName(), out JKLVal value))
{
return(value);
}
else
{
throw new JKLInternalError("Get - Find successful but symbol retrieval failed '" + keySymbol.ToString(true) + "'");
}
}
}
public void Set(JKLSym keySymbol, JKLVal value)
{
// Takes a symbol key and a JKL value and adds them to the environment.
if (!data.TryAdd(keySymbol.getName(), value))
{
// Symbol can shadow an equivalent in an outer scope but cannot be duped.
throw new JKLEvalError("Attempt to redefine '" + keySymbol.ToString(true) + "'");
}
}
// Search for and return the environment (scope) that contains a target symbol.
public Env Find(JKLSym keySymbol)
{
if (data.ContainsKey(keySymbol.getName()))
{
// Symbol exists in the current scope.
return(this);
}
else if (outer != null)
{
// Recurse to search for the symbol in an outer scope.
return(outer.Find(keySymbol));
}
else
{
// Symbol is not defined.
return(null);
}
}
// Setup the REPL.
public REPL()
{
// Load built-in functions into the initial eval environment.
try
{
myEnv = new Env(null);
// Load core functions.
foreach (var thing in JKLNameSpace)
{
JKLSym mSym = new JKLSym(thing.Key);
if (myEnv.Find(mSym) == null)
{
myEnv.Set(mSym, thing.Value);
}
else
{
// The namespace itself may already have thrown an error but if not.
throw new JKLInternalError("Attempt to refine symbol: '" + mSym.ToString(true) + "' with '" + thing.Value.ToString(true) + "'");
}
}
// Load the special eval core function. We have to do it here to access the REPL env.
myEnv.Set(new JKLSym("eval"), new JKLFunc(args =>
{
return(EVAL(args[0], myEnv));
}));
//// EVAL(READ("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \"))\")))))"), myEnv);
//myEnv.Set(new JKLSym("load-file"), new JKLFunc(args =>
//{
// if (args[0] is JKLString mStr)
// {
// try
// {
// string FileText = File.ReadAllText(mStr.unbox());
// // Ee have the text of the file. Now build a file loader to eval.
// StringBuilder sb = new StringBuilder();
// sb.Append("(do ");
// sb.Append(FileText);
// sb.Append(") ");
// return EVAL(read_str(sb.ToString()), myEnv);
// }
// catch (Exception e)
// {
// throw new JKLEvalError("slurp: " + e.Message);
// }
// }
// throw new JKLEvalError("load-file: expected filename but got '" + args[0] + "'");
//}));
// Add 'core' functions defined using JKL itself.
EVAL(READ("(def! *ARGV* (list))"), myEnv);
EVAL(READ("(def! not (fn* (a) (if a false true)))"), myEnv);
// Establish a gensym mechanism
EVAL(READ("(def! *gensym-counter* (atom 0))"), myEnv);
EVAL(READ("(def! gensym (fn* [] (symbol (str \"G__\" (swap! *gensym-counter* (fn* [x] (+ 1 x)))))))"), myEnv);
// This differs from the reference in that it uses a JKL-specific function slurp-do to
// avoid the string quoting problem that can occur when trying to add a (do ... ) form
// around the text retuned by raw slurp.
EVAL(READ("(def! load-file (fn* (f) (eval (read-string (slurp-do f)))))"), myEnv);
EVAL(READ("(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))"), myEnv);
EVAL(READ("(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) (let* (condvar (gensym)) `(let* (~condvar ~(first xs)) (if ~condvar ~condvar (or ~@(rest xs)))))))))"), myEnv);
}
catch (System.TypeInitializationException e)
{
// Typically happens if there is a duplicate symbol in the namespace list
Console.WriteLine("Unrecoverable error: " + e.InnerException.Message);
}
catch (JKLLookupError e)
{
Console.WriteLine(e.Message);
}
catch (JKLEvalError e)
{
Console.WriteLine(e.Message);
}
catch (JKLParseError e)
{
Console.WriteLine(e.Message);
}
}
