public static LinkedListNode <Lexeme> TryParseStruct(LinkedListNode <Lexeme> lexemes, out Stmt resultNode)
{
resultNode = null;
var nextLexeme = DeclStmt.TryParse(lexemes, out var decl);
if (decl != null)
{
resultNode = decl;
return(nextLexeme);
}
return(lexemes);
}
public static LinkedListNode <Lexeme> TryParse(LinkedListNode <Lexeme> lexemes, out DeclStmt resultNode)
{
resultNode = null;
var nextLexeme = Type.TryParse(lexemes, out Type type);
if (type == null)
{
return(lexemes);
}
if (nextLexeme.Value.Type != LT.IDENT)
{
return(lexemes);
}
var nameLexeme = nextLexeme.Value;
nextLexeme = nextLexeme.Next;
if (nextLexeme.Value.Type == LT.OP_ASSIGN)
{
nextLexeme = nextLexeme.Next;
nextLexeme = Expr.TryParse(nextLexeme, out Expr expr);
if (expr == null)
{
throw new Exception($"Missing expression after assignment operator at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
resultNode = new DeclAssignStmt {
Type = type, Value = expr, Token = nameLexeme
};
}
else
{
resultNode = new DeclStmt {
Type = type, Token = nameLexeme
};
}
if (nextLexeme.Value.Type != LT.OP_SC)
{
throw new Exception($"Missing semicolon after statement at {nextLexeme.Value.File}:{nextLexeme.Value.Line}");
}
return(nextLexeme.Next);
}
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);
}
