c# barcode generator open source WHAT DOES SUBSTITUTABILITY REALLY MEAN in Font

Printer QR Code 2d barcode in Font WHAT DOES SUBSTITUTABILITY REALLY MEAN

CHAPTER 24 WHAT DOES SUBSTITUTABILITY REALLY MEAN
Draw QR Code ISO/IEC18004 In None
Using Barcode maker for Font Control to generate, create QR Code image in Font applications.
www.OnBarcode.com
Data Matrix ECC200 Drawer In None
Using Barcode generation for Font Control to generate, create ECC200 image in Font applications.
www.OnBarcode.com
So what about that business of certain method calls succeeding on 64-bit integers but failing on 32-bit ones Presumably what the authors have in mind here is methods such as DOUBLE, where the result of doubling a 32-bit integer might be too large to represent using only 32 bits. All right then: Obviously, the result is of type 64-bit integer, not 32-bit integer. What s the problem 19 Well ... Actually I need to pursue this example a little further. In the previous paragraph, I was tacitly assuming that DOUBLE was an observer, not a mutator. In terms of Tutorial D the language we use to illustrate the ideas of The Third Manifesto DOUBLE might look like this: OPERATOR DOUBLE ( I INT64 ) RETURNS INT64 ; RETURN ( I + I ) ; END OPERATOR ; When invoked, this operator sorry, method has no effect on the argument corresponding to its sole parameter I. And note too that, thanks to LSP, that argument can be of type INT32 as well as INT64. (Of course, I m assuming here that INT32 and INT64 have the obvious semantics and that, pace Liskov and Wing, INT32 is indeed a subtype of INT64.) However, suppose we were to make DOUBLE a mutator instead, thus: OPERATOR DOUBLE ( I INT64 ) UPDATES { I } ; I := I + I ; END OPERATOR ; When this revised DOUBLE operator is invoked, it definitely does have an effect on the argument corresponding to its sole parameter I. And if that argument is of type INT32, not INT64, then the invocation might fail on an overflow error.20 Note: I really need to be a bit more precise here. In our model, the problem under discussion can occur only if the argument is of declared type INT32. If its current most specific type is INT32 but its declared type is INT64, then the problem under discussion doesn t arise. See the subsequent discussion of generalization by constraint. Anyway, it s presumably because of such possibilities (e.g., the possibility that the DOUBLE mutator might give an overflow if invoked on an INT32 object when it doesn t do so on a corresponding INT64 object ) that Liskov and Wing claim that INT32 isn t a subtype of INT64. Instead, they say, in effect, that we need to define a type INT consisting of all possible integers and having two distinct proper subtypes INT32 and INT64, neither of which is a subtype of the other. Then different versions of DOUBLE DOUBLE32 and DOUBLE64, say can be defined, with different preconditions (see later for a discussion of preconditions and postconditions), and the problem goes away. But do you see what s happened We ve been forced into defining what s surely a rather strange and counterintuitive type hierarchy,21 basically because the model doesn t allow objects to change their type as I ll now try to explain.
Barcode Creation In None
Using Barcode generation for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
GS1 - 12 Creator In None
Using Barcode maker for Font Control to generate, create UPCA image in Font applications.
www.OnBarcode.com
19. In our model, the result will actually be of type 64-bit integer only if it is indeed too large to represent using 32 bits; otherwise it ll be of type 32-bit integer. See the subsequent discussion of specialization by constraint. 20. Just as an aside, therefore, I d like to point out that examples like this one can be seen as an argument no pun intended against the idea of mutators in the first place. 21. I don t even want to get into all of the complexities caused by the fact that the two subtypes INT32 and INT64 neither one of which is a subtype of the other, remember overlap, in the sense that many integers (232 of them, to be precise) are values of both types. Let me just observe that overlapping types is yet another topic that our own model does address, gracefully, that isn t even discussed in the Liskov/Wing paper.
Create GTIN - 128 In None
Using Barcode creation for Font Control to generate, create EAN128 image in Font applications.
www.OnBarcode.com
Drawing EAN / UCC - 13 In None
Using Barcode creator for Font Control to generate, create EAN-13 image in Font applications.
www.OnBarcode.com
Printing Barcode In None
Using Barcode creator for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
Make ISSN - 10 In None
Using Barcode encoder for Font Control to generate, create International Standard Serial Number image in Font applications.
www.OnBarcode.com
Creating QR Code In None
Using Barcode generator for Font Control to generate, create QR image in Font applications.
www.OnBarcode.com
QR Code Drawer In Objective-C
Using Barcode creation for iPhone Control to generate, create QR image in iPhone applications.
www.OnBarcode.com
Denso QR Bar Code Drawer In Visual Basic .NET
Using Barcode encoder for .NET framework Control to generate, create QR Code image in .NET framework applications.
www.OnBarcode.com
Paint Code 39 Full ASCII In Java
Using Barcode printer for Java Control to generate, create Code 3/9 image in Java applications.
www.OnBarcode.com
USS Code 39 Recognizer In Visual C#.NET
Using Barcode decoder for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Recognize Barcode In Java
Using Barcode reader for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
Print Code 128 Code Set B In Java
Using Barcode encoder for Android Control to generate, create Code 128A image in Android applications.
www.OnBarcode.com
PDF417 Generation In .NET Framework
Using Barcode encoder for ASP.NET Control to generate, create PDF 417 image in ASP.NET applications.
www.OnBarcode.com
Generate Barcode In Java
Using Barcode maker for Android Control to generate, create Barcode image in Android applications.
www.OnBarcode.com
QR Code 2d Barcode Drawer In None
Using Barcode printer for Online Control to generate, create QR-Code image in Online applications.
www.OnBarcode.com
Printing Quick Response Code In Objective-C
Using Barcode encoder for iPhone Control to generate, create Denso QR Bar Code image in iPhone applications.
www.OnBarcode.com
Encoding QR In Java
Using Barcode drawer for BIRT reports Control to generate, create QR-Code image in Eclipse BIRT applications.
www.OnBarcode.com
Copyright © OnBarcode.com . All rights reserved.