var day : 1 .. 31;
letter : 'A' .. 'Z';
var weight : array[-5 .. 5] of integer; proc set_mode(mode: range[0..3]) ## SPI mode (0-3)All those that existed in Pascal also exist in Ada.
For number ranges you would say
subset HandCountable of Int where 1 <= * <= 5
Like, if I have a variable `i` in range 0...10 and write the Ada equivalent of `i++`, does Ada know that from there on out `i` is in range 1...11? Something like TypeScript's type narrowing?
After 1970, there were less and less innovations in programming languages, in the sense of features that have not existed in any earlier languages.
Many new languages have been introduced since then and some of them might be better than most previous languages, but usually the new languages offer only new combinations of features that have previously existed in different languages and not anything really new.
Ada is important, because in 1979 it included a few features never provided before. Some of those features have been introduced only recently in more popular languages, while others are still missing from most languages.
For anyone who wants to create or improve some programming language, Ada is on a long list of mandatory programming languages that must be understood well, before attempting to do anything that is intended to be better. Sadly, there are many examples of ugly misfeatures in recent programming languages, which demonstrate that their authors were not aware about which was the state of the art 40 years or 50 years ago, and they solved again, but badly, problems that were solved well already in the distant past.
Unfortunately Ada also had defects, some of which were mandated by the Department of Defense requirements.
The defect that is most universally accepted is that it is too verbose.
Another huge barrier (especially to early adoption) was the cost of Ada toolchains.
Even today, there are proprietary Ada implementations that cost thousands of dollars per seat.
Can you give an example of an ADA feature missing from most languages? I know ADA is supposed to be good for writing reliable software, are there any important features related to that which other languages could adopt?
I've seen more misfeatures that seem to come from people not knowing the history of JCL. The lesson would be to plan for expansion of the semantic space.
> The defect that is most universally accepted is that it is too verbose.
It feels less verbose than Java or C#.
I really appreciated the sort of errors the compiler gives you but remember struggling to find good beginner level documentation. I kept landing on more specification-style docs which were more confusing than helpful. Also diving straight into Java after Ada was a shock.
* and variants of Haskell, e.g. Gofer
"I want to point out again the difference between writing a logical and a psychological language. Unfortunately, programmers, being logically oriented, and rarely humanly oriented, tend to write and extol logical languages. Perhaps the supreme example of this is APL. Logically APL is a great language and to this day it has its ardent devotees, but it is also not fit for normal humans to use. In this language there is a game of “one liners”; one line of code is given and you are asked what it means. Even experts in the language have been known to stumble badly on some of them.
A change of a single letter in APL can completely alter the meaning, hence the language has almost no redundancy. But humans are unreliable and require redundancy; our spoken language tends to be around 60% redundant, while the written language is around 40%. You probably think the written and spoken languages are the same, but you are wrong. To see this difference, try writing dialog and then read how it sounds. Almost no one can write dialog so that it sounds right, and when it sounds right it is still not the spoken language.
The human animal is not reliable, as I keep insisting, so low redundancy means lots of undetected errors, while high redundancy tends to catch the errors. The spoken language goes over an acoustic channel with all its noise and must caught on the fly as it is spoken; the written language is printed, and you can pause, back scan, and do other things to uncover the author’s meaning. Notice in English more often different words have the same sounds (“there” and “their” for example) than words have the same spelling but different sounds (“record” as a noun or a verb, and “tear” as in tear in the eye, vs. tear in a dress). Thus you should judge a language by how well it fits the human animal as it is—and remember I include how they are trained in school, or else you must be prepared to do a lot of training to handle the new type of language you are going to use. That a language is easy for the computer expert does not mean it is necessarily easy for the non-expert, and it is likely non-experts will do the bulk of the programming (coding if you wish) in the near future.
What is wanted in the long run, of course, is the man with the problem does the actual writing of the code with no human interface, as we all too often have these days, between the person who knows the problem and the person who knows the programming language. This date is unfortunately too far off to do much good immediately, but I would think by the year 2020 it would be fairly universal practice for the expert in the field of application to do the actual program preparation rather than have experts in computers (and ignorant of the field of application) do the progam preparation.
Unfortunately, at least in my opinion, the ADA language was designed by experts, and it shows all the non-humane features you can expect from them. It is, in my opinion, a typical Computer Science hacking job—do not try to understand what you are doing, just get it running. As a result of this poor psychological design, a private survey by me of knowledgeable people suggests that although a Government contract may specify the programming be in ADA, probably over 90% will be done in FORTRAN, debugged, tested, and then painfully, by hand, be converted to a poor ADA program, with a high probability of errors!"
- Dr. Richard Hamming, "The Art of Doing Science and Engineering..." Written in the late 1990s15 years before Ada, in 1964, IBM PL/I had facilities for multitasking that e.g. included a wait function that could do everything that can be done with WaitForMultipleObjects / WaitForSingleObject. The POSIX threads suck because they lack such a powerful wait function and many other multi-threading libraries, e.g. the C++ standard library, are forced to offer only what is available everywhere, so they do not have anything that is missing in the POSIX threads.
But you can implement an pure userspace or hibrid user/kernel wmo even on top of something like unix poll just fine, so saying that the standard lacks it because of POSIX is wrong.