Slashdot Mirror
Donald Knuth Rips On Unit Tests and More
eldavojohn writes "You may be familiar with Donald Knuth from his famous Art of Computer Programming books but he's also the father of TeX and, arguably, one of the founders of open source. There's an interesting interview where he says a lot of stuff I wouldn't have predicted. One of the first surprises to me was that he didn't seem to be a huge proponent of unit tests. I use JUnit to test parts of my projects maybe 200 times a day but Knuth calls that kind of practice a 'waste of time' and claims 'nothing needs to be "mocked up."' He also states that methods to write software to take advantage of parallel programming hardware (like multi-core systems that we've discussed) are too difficult for him to tackle due to ever-changing hardware. He even goes so far as to vent about his unhappiness toward chipmakers for forcing us into the multicore realm. He pitches his idea of 'literate programming' which I must admit I've never heard of but find it intriguing. At the end, he even remarks on his adage that young people shouldn't do things just because they're trendy. Whether you love him or hate him, he sure has some interesting/flame-bait things to say."
the prize was not US$1000. it started out very small. Knuth did indeed pay out, and indeed doubled it, several times. From wikipedia: "The award per bug started at $2.56 (one "hexadecimal dollar"[24]) and doubled every year until it was frozen at its current value of $327.68. This has not made Knuth poor, however, as there have been very few bugs claimed. In addition, people have been known to frame a check proving they found a bug in TeX instead of cashing it."
That's not literate programming at all. A tad more research on your part is required. I actually remember when "web" in a computing context a literate programming tool rather than that thing you're surfing right now.
Literate Programming interleaves the documentation (written in TeX, naturally) and code into a single document. You then run that (Web) document through one of two processors (Tangle or Weave) to produce code or documentation respectively. The code is then compiled, and the documentation built with your TeX distribution. The documentation includes the nicely formatted source code within.
You can use literate programming in any language you want. I even wrote rules for Microsoft C 7.0's Programmer's Workbench to use it within the MSC environment.
I've frequently thought about going back. Javadoc and/or Sandcastle are poor alternatives.
The snippets have markup to indicate when some snippet needs to come textually before another to keep a compiler happy, but mostly this is figured out automatically. But in general, the resulting C code is in a different order than it appears in the source documentation. For instance, the core algorithm might come first, with all the declarations and other housekeeping at the end. (With documentation about why you're using this supporting library and not that, of course.)
Literate Programming is not about making programming languages incredibly verbose; it's about *describing* your program in a normal, human way, by explaining it step by step and quoting bits and pieces of the program. Sounds ideal from a documentation point of view, right ? only that if that was all there was with Literate Programming, it would be a stupid idea, as documentation has a nasty habit to not follow up with code modification.
... and then remove all the green inputs:
:-P
The really cool idea with LP is that the code snippets you use in the documentation are then weaved together to generate the "real" code of your program. So a LP document is BOTH the documentation and the code. A code snippet can contains references ("include") to other code snippets, and you can adds stuff to an existing code snippet.
Let me show you an example in simple (invented) syntax:
{my program}
{title}My super program{/title}
Blablabla we'd need to have the code organized in the following loop:
{main}:
{for all inputs}:
{filter inputs}
{apply processing on the filtered inputs}
{/}
{/}
The {for all inputs} consist in the following actions:
{for all inputs}:
some code
{/}
The filtering first remove all blue inputs:
{filter inputs}:
remove all blue inputs
{/}
{filter inputs}+:
remove all green inputs
{/}
etc.
{/}
The above is purely to illustrate the idea, the actual CWEB syntax is a bit different. But you can see how, starting with a single source document, you could generate both the code and the documentation of the code, and how you can introduce and explain your code gradually, explaining things in whichever way that makes the most sense (bottom-up, top-down, a mix of those..).
In a way, Doxygen or JavaDoc have similar goals: put documentation and code together and generate documentation. But they take the problem in reverse from what literate programming propose; with Doxygen/JavaDoc, you create your program, put some little snippets of documentation, and you automatically generate a documentation of your code. With LP, you write your documentation describing your program and you generate the program.
Those two approaches produce radically different results -- the "documentation" created by Doxygen/JavaDoc is more a "reference" kind of documentation, and does little to explain the reason of the program, the choice leading to the different functions or classes, or even something as important as explaining the relationships between classes. With some effort it's possible to have such doc system be the basis of nice documentation (Apple Cocoa documentation is great in that aspect for example), but 1/ this requires more work (Cocoa has descriptive documents in addition to the javadoc-like reference) 2/ it really only works well for stuff like libraries and frameworks.
LP is great because the documentation is really meant for humans, not for computers. It's also great because by nature it will produces better documentation and better code. It's not so great as it poorly integrates with the way we do code nowadays, and it poorly integrates with OOP.
But somehow I've always been thinking that there is a fundamentally good idea to explore there, just waiting for better tools/ide to exploit it
(also, the eponymous book from Knuth is a great read)
The GP must have been confused by the example on Wikipedia, which a) wasn't literate programming and b) used a shitty made-up language where "multiplyby" was one of the operators. Literate programming is programming (in your favourite language) with a code-in-documentation approach instead of the usual documentation-in-code approach. So, for example, the flow of your literate program is defined by how best to explain what's happening to a human reader, rather than being constrained by the order the compiler requires. You run your literate program through a tool and it spits out compilable code or pretty documentation.
It's called ravioli code
The world has changed and we all have become metal men.