Bruce Eckel’s recent blog post on the legacy left by C++ and Java generated a lot of reaction. While mentioning some design mistakes, he concludes that both languages have had a significant role in programming languages evolution and an important positive legacy. But is it not too early to talk about their legacy?
Eckel, a former member of the C++ Standards Committee, recollects the decision made regarding backward compatibility of the language with C from the beginning:
To understand how the language can be both unpleasant and complicated, and well designed at the same time, you must keep in mind the primary design decision upon which everything in C++ hung: compatibility with C. Stroustrup decided -- and correctly so, it would appear -- that the way to get the masses of C programmers to move to objects was to make the move transparent: to allow them to compile their C code unchanged under C++.
While C++ did succeed to attract most C developers to C++, the compatibility decision had a severe negative impact on language’s evolution:
This [compatibility with C] was a huge constraint, and has always been C++'s greatest strength ... and its bane. It's what made C++ as successful as it was, and as complex as it is.
For example, he acknowledges that operator overloading is difficult to use in C++:
They [those who did not understand C++ well enough] thought operator overloading was too hard for programmers to use properly. Which is basically true in C++, because C++ has both stack allocation and heap allocation and you must overload your operators to handle all situations and not cause memory leaks. Difficult indeed.
Of course, such statements are doomed to spark a debate. Archilleas Margaritis does not consider C compatibility should be an issue:
I don't think that C++ is badly designed because of compatibility with C. ADA is compatible with C, but it is a very good language, with strong engineering leading its design.
What is wrong with C++ is source code level compatibility with C. In order to be able to include C headers, C++ maintained the preprocessor system of C. That led to a strange non-context free grammar, which led to a very strange syntax which had to stay compatible with C.
Michele Costabirle considers that missing a standard library from the beginning was one of C++ flaws:
I think that one serious burden of C++ was the lack of a standard library.
If I recall it right, Stroustroup wrote in "The Design and Evolution of C++" that he delayed a standard library in favor of multiple inheritance. I would have enjoyed it more the other way.
Many things can be said regarding C++, but one thing is sure: C++ moved programmers one step up on the programming ladder.
Talking about a different language but on the same tone, Eckel reiterates some of the design mistakes done with Java:
For many years, the partly line from the Java team was "Operator overloading is too complicated." This and many other decisions where someone clearly didn't do their homework is why I have a reputation for disdaining many of the choices made by Gosling and the Java team. …
Primitives "had to be included for efficiency." The right answer is to stay true to "everything is an object" and provide a trap door to do lower-level activities when efficiency was required (this would also have allowed for the hotspot technologies to transparently make things more efficient, as they eventually would have). Oh, and the fact that you can't use the floating point processor directly to calculate transcendental functions (it's done in software instead). …
When I wrote about how badly generics were designed, I got the same response, along with "we must be backwards compatible with previous (bad) decisions made in Java." Lately more and more people have gained enough experience with Generics to see that they really are very hard to use
Bill Venners remembers things differently:
I'm not sure where you got the impression that the choice of leaving out operator overloading was because someone didn't do their homework. I remember asking this Gosling in one of my interviews of him why he left out operator overloading (I don't think that question and answer ended up getting published). What he basically said to me, is what I heard him say in other contexts: Gosling felt that the level of operator overloading abuse he had seen in practice in other languages (I'm not sure if this was just C++, but certainly included C++) had outweighed the benefits of it. That's all. It was a subjective design choice.
James Watson favors the limitations purposely introduced in Java:
What has made Java a good fit for these shops is that it is easy to follow Java code. Yeah, you can write unmaintainable code in any language but you have to work at it in Java. It doesn't provide a lot of the features that are so easy to abuse in other languages.
From an individual's perspective, this is terrible. If I don't want to use a feature I won't use it. Who is Sun to tell me what I should do and shouldn't do? But when you take a group of developers who have different ideas about what a good approach is, the game changes. Having a limited number of ways to do things starts making sense.
Noel Grandin added his bit, broadening the debate even more by including new languages:
Most of the other "hot" languages like Ruby, Scala are never going to hit mainstream, because they're all biased to heavily in favor of writing code, instead of reading code.
Java got this balance correct - Java might be verbose and lack lots of "cool" features, but it's really easy to figure out what some random code is doing.
In the end, Eckel talked about Java’s legacy:
Java brought the mainstream of programmers into the world of garbage collection, virtual machines and a consistent error handling model (especially if you subtract checked exceptions, which is possible using techniques I show in Thinking in Java, 4e). With all its flaws, it moved us up a level, to the point where we are now ready for higher-level languages.
The most positive factor is preparing the way for future languages:
At one point, C++ was the leading language and people thought it would always be so. Many think the same about Java, but Java has made it even easier to replace itself, because of the JVM. It's now possible for someone to create a new language and have it run as efficiently as Java. …
And we are seeing this happen -- both with higher-level static languages like Scala, and with dynamic languages, both new and ports, like Groovy, JRuby and Jython. …
The unintentional benefit, the true accidental brilliance of Java is that it has created a very smooth path for its own replacements, even if Java itself has reached the point where it can no longer evolve. All future languages should learn from this: either create a culture where you can be refactored (as Python and Ruby have done) or allow competitive species to thrive.
Java ignited many disputes when it appeared, especially between C++ and newly formed Java developers. Voices have calmed down since then, and we can see clearer now where we stand and what is the legacy left by both languages. Or maybe is it too early to talk about their legacy? It sounds a bit like they are dead or dying languages. (Opinions are welcome as always.)