// AnalyzeLetStar returns a Block with vars, each initialized in the order
// they appear. Each var's init expr can refer to vars initialized before it.
// The Block's body is the Let*'s body.
//
public static Expression AnalyzeLetStarExpr(SymplLetStarExpr expr,
AnalysisScope scope)
{
var letscope = new AnalysisScope(scope, "let*");
// Analyze bindings.
List <Expression> inits = new List <Expression>();
List <ParameterExpression> varsInOrder = new List <ParameterExpression>();
foreach (var b in expr.Bindings)
{
// Need richer logic for mvbind
var v = Expression.Parameter(typeof(object), b.Variable.Name);
varsInOrder.Add(v);
inits.Add(
Expression.Assign(
v,
Expression.Convert(AnalyzeExpr(b.Value, letscope), v.Type))
);
// Add var to scope after analyzing init value so that init value
// references to the same ID do not bind to his uninitialized var.
letscope.Names[b.Variable.Name.ToLower()] = v;
}
List <Expression> body = new List <Expression>();
foreach (var e in expr.Body)
{
body.Add(AnalyzeExpr(e, letscope));
}
// Order of vars to BlockExpr don't matter semantically, but may as well
// keep them in the order the programmer specified in case they look at the
// Expr Trees in the debugger or for meta-programming.
inits.AddRange(body);
return(Expression.Block(typeof(object), varsInOrder.ToArray(), inits));
}
public static Expression AnalyzeBinaryExpr(SymplBinaryExpr expr,
AnalysisScope scope)
{
// The language has the following special logic to handle And and Or
// x And y == if x then y
// x Or y == if x then x else (if y then y)
if (expr.Operation == ExpressionType.And)
{
return(AnalyzeIfExpr(
new SymplIfExpr(
expr.Left, expr.Right, null),
scope));
}
else if (expr.Operation == ExpressionType.Or)
{
// Use (LetStar (tmp expr) (if tmp tmp)) to represent (if expr expr)
// to remore duplicate evaluation.
// So x Or y is translated into
// (Let* (tmp1 x)
// (If tmp1 tmp1
// (Let* (tmp2 y) (If tmp2 tmp2))))
//
IdOrKeywordToken tmp2 = new IdOrKeywordToken(
// Real implementation needs to ensure unique ID in scope chain.
"__tmpLetVariable2");
var tmpExpr2 = new SymplIdExpr(tmp2);
var binding2 = new LetBinding(tmp2, expr.Right);;
var ifExpr2 = new SymplIfExpr(
tmpExpr2, tmpExpr2, null);
var letExpr2 = new SymplLetStarExpr(
new[] { binding2 },
new[] { ifExpr2 });
IdOrKeywordToken tmp1 = new IdOrKeywordToken(
// Real implementation needs to ensure unique ID in scope chain.
"__tmpLetVariable1");
var tmpExpr1 = new SymplIdExpr(tmp1);
LetBinding binding1 = new LetBinding(tmp1, expr.Left);;
SymplExpr ifExpr1 = new SymplIfExpr(
tmpExpr1, tmpExpr1, letExpr2);
return(AnalyzeLetStarExpr(
new SymplLetStarExpr(
new[] { binding1 },
new[] { ifExpr1 }
),
scope
));
}
return(Expression.Dynamic(
scope.GetRuntime().GetBinaryOperationBinder(expr.Operation),
typeof(object),
AnalyzeExpr(expr.Left, scope),
AnalyzeExpr(expr.Right, scope)
));
}