public static LinkedListNode <Lexeme> TryParse(LinkedListNode <Lexeme> lexemes, out AssignStmt resultNode, bool needSC = true)
{
resultNode = null;
var nextLexeme = Var.TryParse(lexemes, out Var lhs);
if (lhs == null)
{
return(lexemes);
}
AssignOp op = AssignOp.ASSIGN;
if (nextLexeme.Value.Type == LT.OP_ADD || nextLexeme.Value.Type == LT.OP_SUB ||
nextLexeme.Value.Type == LT.OP_MUL || nextLexeme.Value.Type == LT.OP_DIV ||
nextLexeme.Value.Type == LT.OP_MOD)
{
op = TypeToOp(nextLexeme.Value.Type);
nextLexeme = nextLexeme.Next;
}
if (nextLexeme.Value.Type != LT.OP_ASSIGN)
{
return(lexemes);
}
Lexeme token = nextLexeme.Value;
nextLexeme = Expr.TryParse(nextLexeme.Next, out Expr rhs);
if (rhs == null)
{
throw new Exception($"Unrecognized right hand member of operator '{OpName(op)}' at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
if (needSC)
{
if (nextLexeme.Value.Type != LT.OP_SC)
{
throw new Exception($"Missing semicolon after statement at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
nextLexeme = nextLexeme.Next;
}
resultNode = new AssignStmt {
LHS = lhs, RHS = rhs, Op = op, Token = token
};
return(nextLexeme);
}
public static LinkedListNode <Lexeme> TryParse(LinkedListNode <Lexeme> lexemes, out ForLoop resultNode)
{
resultNode = null;
if (lexemes.Value.Type != LT.KW_FOR)
{
return(lexemes);
}
var nextLexeme = lexemes.Next;
if (nextLexeme.Value.Type != LT.OP_PAREN_O)
{
throw new Exception($"Missing loop header at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
nextLexeme = nextLexeme.Next;
nextLexeme = DeclStmt.TryParse(nextLexeme, out DeclStmt ds);
if (ds == null || !(ds is DeclAssignStmt init))
{
throw new Exception($"Cannot parse loop initializer at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
nextLexeme = BinaryExpr.TryParseExpr(nextLexeme, out Expr cond);
if (cond == null)
{
throw new Exception($"Cannot parse loop condition at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
if (nextLexeme.Value.Type != LT.OP_SC)
{
throw new Exception($"Missing semicolon after loop condition at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
nextLexeme = nextLexeme.Next;
nextLexeme = AssignStmt.TryParse(nextLexeme, out AssignStmt upd, false);
if (upd == null)
{
throw new Exception($"Cannot parse loop afterthought at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
if (nextLexeme.Value.Type != LT.OP_PAREN_C)
{
throw new Exception($"Missing closing parenthesis for loop header at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
nextLexeme = nextLexeme.Next;
Stmt stmt;
List <Stmt> stmts = new List <Stmt>();
if (nextLexeme.Value.Type == LT.OP_BRACE_O)
{
// block body
nextLexeme = nextLexeme.Next;
nextLexeme = Stmt.TryParse(nextLexeme, out stmt);
while (stmt != null)
{
stmts.Add(stmt);
nextLexeme = Stmt.TryParse(nextLexeme, out stmt);
}
if (nextLexeme.Value.Type != LT.OP_BRACE_C)
{
throw new Exception($"Missing closing bracket for loop body at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
nextLexeme = nextLexeme.Next;
}
else
{
// single statement body
nextLexeme = Stmt.TryParse(nextLexeme, out stmt);
if (stmt == null)
{
throw new Exception($"Missing loop body at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
stmts.Add(stmt);
}
resultNode = new ForLoop
{
Init = init,
Condition = cond,
Update = upd,
Body = new BlockBody(stmts)
};
return(nextLexeme);
}
public static LinkedListNode <Lexeme> TryParse(LinkedListNode <Lexeme> lexemes, out Stmt resultNode)
{
resultNode = null;
if (lexemes.Value.Type == LT.OP_SC)
{
resultNode = new BlankStmt();
return(lexemes.Next);
}
var nextLexeme = IfStmt.TryParse(lexemes, out IfStmt sif);
if (sif != null)
{
resultNode = sif;
return(nextLexeme);
}
nextLexeme = TryParseStruct(lexemes, out Stmt stmt);
if (stmt != null)
{
resultNode = stmt;
return(nextLexeme);
}
nextLexeme = FnCall.TryParse(lexemes, out FnCall fnc);
if (fnc != null)
{
if (nextLexeme.Value.Type == LT.OP_SC)
{
resultNode = new ExprStmt <FnCall>(fnc);
return(nextLexeme.Next);
}
}
nextLexeme = ForLoop.TryParse(lexemes, out ForLoop fl);
if (fl != null)
{
resultNode = fl;
return(nextLexeme);
}
nextLexeme = WhileLoop.TryParse(lexemes, out WhileLoop wl);
if (wl != null)
{
resultNode = wl;
return(nextLexeme);
}
nextLexeme = AssignStmt.TryParse(lexemes, out AssignStmt sa);
if (sa != null)
{
resultNode = sa;
return(nextLexeme);
}
nextLexeme = ReturnStmt.TryParse(lexemes, out ReturnStmt sr);
if (sr != null)
{
resultNode = sr;
return(nextLexeme);
}
if (lexemes.Value.Type == LT.KW_BREAK)
{
if (lexemes.Next.Value.Type != LT.OP_SC)
{
throw new Exception($"Missing semicolon after break keyword at {lexemes.Value.File}:{lexemes.Value.Line}");
}
resultNode = new BreakStmt {
Token = lexemes.Value
};
return(lexemes.Next.Next);
}
if (lexemes.Value.Type == LT.KW_CONT)
{
if (lexemes.Next.Value.Type != LT.OP_SC)
{
throw new Exception($"Missing semicolon after continue keyword at {lexemes.Value.File}:{lexemes.Value.Line}");
}
resultNode = new ContinueStmt {
Token = lexemes.Value
};
return(lexemes.Next.Next);
}
return(lexemes);
}