protected override void PrintExpr(string argNameVarPrompt, Exprs.Expr e) => WriteLine($"{argNameVarPrompt} {e}");
//protected override void PrintExpr(string argNameVarPrompt, Exprs.Expr e)=>mFrm.pri public override void PrintExprOut(string argNameVarPrompt, Exprs.Expr e) => mFrm.PrintExprOut(argNameVarPrompt, e);