private Stmt IfStmt()
{
Expr cond = ParseExpr();
Stmt thenBranch = Block();
if (IsToken("else"))
{
EatToken();
Stmt elseBranch = Block();
IfElseStmt stmt = new IfElseStmt();
stmt.Cond = cond;
stmt.Then = thenBranch;
stmt.Else = elseBranch;
return(stmt);
}
else
{
IfStmt stmt = new IfStmt();
stmt.Cond = cond;
stmt.Then = thenBranch;
return(stmt);
}
}
private void GenStmt(Stmt stmt, Env table, ILGenerator il)
{
if (stmt is Sequence)
{
Sequence seq = (Sequence)stmt;
GenStmt(seq.First, table, il);
GenStmt(seq.Second, table, il);
}
else if (stmt is ImportStmt)
{
// 只能导入.Net模块
ImportStmt import = (ImportStmt)stmt;
Reflect.Assembly asm = null;
if (import.Name == "System")
{
// 首先在核心模块中查找
// 获取int类型所在的程序集(mscorlib.dll)
asm = Reflect.Assembly.GetAssembly(typeof(int));
}
else
{
string root = Framework.GetFrameworkDirectory();
string assembly = IO.Path.Combine(root, import.Name + ".dll");
asm = Reflect.Assembly.LoadFile(assembly); // TODO 错误处理
}
table.AddModule(new Module(import.Name, asm));
}
else if (stmt is DeclareVar)
{
DeclareVar declare = (DeclareVar)stmt;
Type type = declare.Type;
if (type == null)
{
type = TypeOfExpr(declare.Expr, table);
}
if (table.IsDeclared(declare.Name))
{
throw new Exception(String.Format("A local variable named '{0}' is already defined in this scope", declare.Name));
}
// TODO 保存本地变量的位置索引
table[declare.Name] = new LocalVariable(il.DeclareLocal(type));
// set the initial value
BinaryExpr be = new BinaryExpr();
Variable var = new Variable();
var.Name = declare.Name;
be.Left = var;
be.Op = "=";
if (declare.Expr is Undefined)
{
// FIXME 根据所声明变量的类型赋初值
IntLiteral expr = new IntLiteral();
expr.Value = 0;
be.Right = expr;
}
else
{
be.Right = declare.Expr;
}
GenExpr(be, table, il);
}
else if (stmt is Return)
{
Return ret = (Return)stmt;
GenExpr(ret.Expr, table, il);
}
else if (stmt is Function)
{
// 定义全局函数
DefineGlobalMethod((Function)stmt, table);
}
else if (stmt is Print)
{
Print print = (Print)stmt;
GenExpr(print.Expr, table, il);
Reflect.MethodInfo mi = typeof(Console).GetMethod("WriteLine", new Type[] { TypeOfExpr(print.Expr, table) });
il.Emit(OpCodes.Call, mi);
}
else if (stmt is IfStmt)
{
IfStmt ifStmt = (IfStmt)stmt;
// 代码块的结束位置
Label End = il.DefineLabel();
// 生成条件表达式
GenExpr(ifStmt.Cond, table, il);
il.Emit(OpCodes.Brfalse, End);
// then代码块
//il.BeginScope();
GenStmt(ifStmt.Then, table, il);
//il.EndScope();
il.MarkLabel(End);
}
else if (stmt is IfElseStmt)
{
IfElseStmt ifElseStmt = (IfElseStmt)stmt;
// 分支标签
Label ThenEnd = il.DefineLabel();
Label End = il.DefineLabel();
// 条件表达式
GenExpr(ifElseStmt.Cond, table, il);
il.Emit(OpCodes.Brfalse, ThenEnd);
// then分支
GenStmt(ifElseStmt.Then, table, il);
il.Emit(OpCodes.Br, End);
il.MarkLabel(ThenEnd);
// else分支
GenStmt(ifElseStmt.Else, table, il);
il.MarkLabel(End);
}
else if (stmt is WhileLoop)
{
WhileLoop whileLoop = (WhileLoop)stmt;
Label LoopStart = il.DefineLabel();
Label LoopEnd = il.DefineLabel();
il.MarkLabel(LoopStart);
GenExpr(whileLoop.Cond, table, il);
il.Emit(OpCodes.Brfalse, LoopEnd);
GenStmt(whileLoop.Body, table, il);
il.Emit(OpCodes.Br, LoopStart);
il.MarkLabel(LoopEnd);
}
//else if (stmt is ForLoop)
//{
// ForLoop forLoop = (ForLoop)stmt;
// Assign assign = new Assign();
// assign.Ident = forLoop.Name;
// assign.Expr = forLoop.From;
// GenStmt(assign, table, il);
// // jump to the test
// Label test = il.DefineLabel();
// il.Emit(OpCodes.Br, test);
// // statements in the body of the for loop
// Label body = il.DefineLabel();
// il.MarkLabel(body);
// GenStmt(forLoop.Body, table, il);
// // to (increment the value of x)
// il.Emit(OpCodes.Ldloc, table[forLoop.Name]);
// il.Emit(OpCodes.Ldc_I4, 1);
// il.Emit(OpCodes.Add);
// Store(forLoop.Name, table, il);
// // **test** does x equal 100? (do the test)
// il.MarkLabel(test);
// il.Emit(OpCodes.Ldloc, table[forLoop.Name]);
// GenExpr(forLoop.To, table, il);
// il.Emit(OpCodes.Blt, body);
//}
//else if (stmt is Expr)
//{
// GenExpr((Expr)stmt, table, il);
//}
else if (stmt is Simple)
{
Simple simple = (Simple)stmt;
GenExpr(simple.Expr, table, il);
// TODO 无括号的函数调用
}
else if (stmt is EmptyStmt)
{
// empty statement
// do nothing
}
else
{
throw new Exception("don't know how to gen a " + stmt.GetType().Name);
}
}