I was speaking with a friend the other day and we were talking about the interaction of effects and how to explain them.

One informal way to explain some additions to languages are that they are scale down localized structured versions of features that were largely available for the whole program. Let me explain: Did you start programming with an imperative language with global variables? (There is one called C that affected the minds of many people.) When you switch to an object oriented language, someone might have explained to you that there is no longer any need for real global variables. You may make these wannabe globals members of a class. You can turn methods that need the globals into members of that class as well. So they are global as far as the methods in question go, but they are not truly global.

In much the same way, we can explain yield. Programming languages have always had input and output operators - scanf-printf, gets-puts etc. However these operators are global with respect to your program. When you execute a printf, it is the output of the whole program, not of any one part of it. Yield on the other hand can be thought of as a localized input output operator. You can yield values from one part of the program to another part of the program. You get input from one part of the program. A method that yields is a packaged up opaque entity, a little sub-program, that communicates using yield with its consuming-context, the rest of the program.

We can explain exceptions in this way as well. In the absence of exceptions when there was a fault, the whole program would come down. It would core dump, modulo global error handlers. The whole machine does not come down, just the program that faults does. The environment that hosts the program may realize that there is a fault and do something about it. Its much the same with exceptions, but with the difference that only a part of the program "core dumps". Its a localized failure of the program that the environment (the rest of the program) can handle (or not handle, thereby making it a global failure).

So can you play this game or any other global program features, turning them into powerful localized structured operators?

After talking to Pooja, I felt it necessary to mention the great mathematician G. H. Hardy on my blog. Hardy is most famous outside of mathematics for his "A Mathematician's Apology". The book, written in later in life by Hardy, talks among aother things about how mathematics is young man's game. He is also somewhat know for his association with Ramanujan and for being the person responsible for bringing him to Cambridge where his greatest mathematics unfolded.

Quoting one of the mathematicians, C Snow, that Hardy worked with:
http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Hardy.html

A mathematicians apology is, if read with the textual attention it deserves, a book of haunting sadness. Yes, it is witty and sharp with intellectual high spirits: yes, the crystalline clarity and candour are still there: yes, it is the testament of a creative artist. But it is also, in an understated stoical fashion, a passionate lament for creative powers that used to be and that will never come again. I know nothing like it in the language: partly because most people with the literary gift to express such a lament don't come to feel it: it is very rare for a writer to realise, with the finality of truth, that he is absolutely finished.

Hardy was a sort of purist mathematician, one who did his mathematics not for the sake of its applicability to anything, but for the sake of doing great mathematics. Hardy, along with Littlewood and Ramanujan,  is also mention in Apostolos Doxiadis' "Uncle Petros and the Goldbach Conjecture". The link above gives a short summary on his life.

Some quotes:

Asked if he believes in one God, a mathematician answered: "Yes, up to isomorphism".

http://en.wikipedia.org/wiki/G._H._Hardy:

It is never worth a first class man's time to express a majority opinion. By definition, there are plenty of others to do that.

A mathematician, like a painter or a poet, is a maker of patterns. If his patterns are more permanent than theirs, it is because they are made with ideas.

Many years back I worked full time at Microsoft on one of the many projects related to Vista (or what was then called Longhorn). Last December I was visiting friends in the Redmond area when one of the jokingly observed how the code I had written for Microsoft still hadn't seen light of day, while two and a half years later, I had moved on and completed my Masters and had started on my PhD.

This wasn't a sort of accidental slip, but I remember we were told at that time that if we had any ideas to suggest for Vista, they better be ideas that will be new and interesting 3-4 years later when the OS actually ships. This is a tall order for any sort of idea, much less for the volatile world of "software project" ideas.

While this seemed like very ironic humor at that time, over the past month or so, once in a while I thought about what that meant. After all, I had spent a year writing all that code. A very busy year at that - I had spent 15+ hours a day, I daresay, that was my average day, struggling with the turmoil of the massive engineering effort that was Vista.

I wasn't a *great* programmer by many standards, but I'd like to think that I was better than many I had encountered. 15+ hours of my time for about a year, took a lot of out of my life and it didn't seem to have amounted to anything! Sure I was being paid a handsomely, but one one like to think that one's efforts contribute to the world in some way as well. After all that year was full of deadlines and things being rushed to be completed and such. What came of all of it? If it came to nothing, what a waste of life that was...

A few weeks back, I got a call from Steve who works with Google (who has a fascinating blog btw), about coming back and working with them on some stuff. I casually asked what happened about the last thing I had worked on, when I was there last summer. I had made some extensions to the Rhino compiler, the largest part of which was adding the yield control operator to it. Steve said that they were using it. Somewhere in the back of my mind I said "What?!".

Maybe my programming has matured over the years. Maybe the ~6 hrs a day I spent in office as an intern produced production quality code. I somehow assumed that it wouldn't see any real world use. Was it really that special that it was ready for real world use? Don't get me wrong, it wasn't bad code. But it was code that only written, not "baked" for years.

Maybe there was another reason. Maybe, it wasn't a property of the code at all, but of the fact that there was something radically different about the outlooks of both these companies. There are many thing one can say about this "difference in outlook", positive and negative things things about both. But a shift that causes developers to feel effective by default as opposed to feeling ineffective by default, is an empowering thought. "If I build it for you, what will become of it?"

Maybe mine was an isolated case of wasted engineering effort and this is nitpicking. If that's so, I'll be happy for it.