public static object Eval(Evaluator v, InvocationExpr e)
{
if (e.Count != 1)
{
throw new Exception("`eval` requires 1 parameter");
}
var quoteExpr = e[0] as QuoteExpr;
if (quoteExpr == null)
{
throw new Exception("`eval` parameter must be a quoted s-expression");
}
return(v.Eval(((QuoteExpr)quoteExpr).SExpr));
}
public static object If(Evaluator v, InvocationExpr e)
{
if (e.Count != 3)
{
throw new Exception("`if` requires 3 parameters: condition, then, else");
}
var testExpr = e[0];
var trueExpr = e[1];
var falseExpr = e[2];
// Eval the test s-expression:
var test = v.Eval(testExpr);
if (test == null)
{
// Null is logically false:
return(v.Eval(falseExpr));
}
else
{
// Check if the test value is a boolean or not:
if (test is bool)
{
// Test the boolean value:
if ((bool)test)
{
return(v.Eval(trueExpr));
}
else
{
return(v.Eval(falseExpr));
}
}
else if (!test.GetType().IsValueType)
{
// Non-null reference is logically true:
return(v.Eval(trueExpr));
}
else
{
throw new Exception("`if` condition parameter must be a boolean or reference type");
}
}
}
public static object Ne(Evaluator v, InvocationExpr e)
{
if (e.Count != 2)
{
throw new Exception("`ne` requires 2 parameters");
}
var a = v.Eval(e[0]);
var b = v.Eval(e[1]);
if (a == null && b == null)
{
return(false);
}
else if (a == null || b == null)
{
return(true);
}
else
{
return(!a.Equals(b));
}
}
public object Invoke(InvocationExpr e)
{
if (e.Identifier.Kind == SExprKind.ScopedIdentifier)
{
// Check the function name:
var name = ((ScopedIdentifierExpr)e.Identifier).Name.Text;
// TODO(jsd): Support CLR property/method invocation for objects!
// Find the function in the `externs` dictionary:
ExternFunction func;
if (!externs.TryGetValue(name, out func))
{
throw new Exception("Undefined function '{0}'".F(name));
}
// Execute it:
return(func(this, e));
}
else if (e.Identifier.Kind == SExprKind.StaticMemberIdentifier)
{
// Find the type by namespace/class:
var ident = (StaticMemberIdentifierExpr)e.Identifier;
var typeName = String.Join(".", ident.TypeName.Select(ns => ns.Text));
var memberName = ident.Name.Text;
var type = Type.GetType(typeName, false);
if (type == null)
{
throw new Exception("Could not find type by name '{0}'".F(typeName));
}
// Member can be either a method or property:
// Find a method:
var mt = type.GetMethod(memberName);
if (mt != null)
{
object[] parms;
if (e.Count > 0)
{
parms = Eval(e.Parameters);
}
else
{
parms = null;
}
// TODO(jsd): handle invocation exception:
return(mt.Invoke(null, parms));
}
// Find a property:
var pr = type.GetProperty(memberName);
if (pr != null)
{
// TODO(jsd): Turn this into a property reference expression so we can (set x) it.
if (e.Count > 0)
{
var parms = Eval(e.Parameters);
return(pr.GetValue(null, parms));
}
else
{
return(pr.GetValue(null));
}
}
throw new Exception("Could not find method or property with name '{0}' on instance of type '{1}'".F(memberName, type.FullName));
}
else if (e.Identifier.Kind == SExprKind.InstanceMemberIdentifier)
{
// Find the type by namespace/class:
var ident = (InstanceMemberIdentifierExpr)e.Identifier;
var memberName = ident.Name.Text;
var instance = Eval(e[0]);
if (instance == null)
{
throw new Exception("Cannot call method or property '{0}' on a null object instance".F(memberName));
}
var type = instance.GetType();
// Member can be either a method or property:
// Evaluate parameter expressions:
var parmExprs = e.Parameters.Skip(1).ToArray();
object[] parms;
Type[] parmTypes;
if (parmExprs.Length > 0)
{
parms = Eval(parmExprs);
parmTypes = parms.Select(p => p == null ? (Type)null : p.GetType()).ToArray();
}
else
{
parms = null;
parmTypes = Type.EmptyTypes;
}
// Find a method:
var mt = type.GetMethod(memberName, parmTypes);
if (mt != null)
{
// TODO(jsd): handle invocation exception:
return(mt.Invoke(instance, parms));
}
// Find a property:
var pr = type.GetProperty(memberName);
if (pr != null)
{
// TODO(jsd): Turn this into a property reference expression so we can (set x) it.
return(pr.GetValue(instance, parms));
}
throw new Exception("Could not find method or property with name '{0}' on instance of type '{1}'".F(memberName, type.FullName));
}
throw new Exception("Unknown or unsupported member identifier kind '{0}'".F(e.Identifier.Kind));
}