Maximally Powerful, Minimally Useful
blog.higher-order.com
blog.higher-order.com
One of the core features of functional programming is “recursion schemes”, that is, generalising patterns of data flow. While “goto” lets you manipulate control flow arbitrarily, it turns out that you don’t usually want arbitrary control flow—and the same is true for data, so rather than “for” loops, it’s often easier to think in terms of the common patterns: “map”, “reduce”, “filter”.
It is. My lament there is that, at least in my experience, optimizers haven't caught up in this department. So while I invariably start with the higher-order operations, all too often the profiler subsequently informs me that I need to replace that code with a for loop.
I suspect that side effects are the culprit there: In a language without referential transparency, the optimizer's very limited in what kinds of reasoning it can make about a function. I'm not quite ready to give up side effects just yet, though. I wish I could work in a language that only allows them in functions that explicitly declare that they want to use them, though.
That’s what Haskell does. The big scary M-word just gives you all the other features you end up wanting from your effect system once you have one. See my explanation here: http://programmers.stackexchange.com/questions/258011/altern...
This exact point (comprehensibility vs. power) is why Smalltalk is so amazing: it adds a lot of power while at the same time being more comprehensible, not less. That's no small feat, and IMHO one that is both under-appreciated and under-analyzed.
EDIT: Of course, see "The Power of Simplicity" http://www.selflanguage.org/_static/published/self-power.pdf
Essentially, you have a tension between laws a models. A larger number of laws means more reasoning power at the expense of fewer models (possibly 0 in which case you're inconsistent). A larger number of models means greater realizability but fewer laws (possibly 0 in which case you've gained nothing through this exercise).
It's always a game of comparative linguistics—does this abstraction pay its way? Well, without it we have this set of laws and with it we gain this new set. Are things in balance such that the abstraction is realizable and the laws are meaningful? That's your tradeoff.
An interesting analog in the arts is the notion that a chosen or imposed constraint can provoke creativity and open up new possibilities.
With it you can basically choose your level of expressiveness while you develop your program (with different levels for different parts of your program). The frustrating trade-off between expressiveness and readability[2] is the main reason I love this paradigm. Unfortunately LOP has never been really trendy. Hope it will change soon.
[1] http://en.wikipedia.org/wiki/Language-oriented_programming
[2] For programming languages I would rather speak of readability (as opposed to analyzability) because a program is often not written in stone but "alive" (it's modified, enhanced over time...). It probably does not apply to the other fields discussed in the article though.
It's extremely easy to do LOP with Lisp thanks to s-expressions (all those parenthesis :). But you can be much more expressive with LOP.
EDIT: elaborating
If you ban (for your whole program) some components then I guess you would loose some expressiveness.
Also I don't know if you can categorize "components" as more or less readable. For some problems a "component" might be highly readable while totally inappropriate for another problem. I see some cases where using more components makes the code more readable.
This is an art of using language features (paradigms etc...) and design patterns that will be the most readable while powerful enough to solve your problem. I love doing it with Lisp or Ruby which are languages with a very modular syntax. But it's time consuming so I'm doing it only for substantial projects I really care about. It's much more efficient to use conventional well established programming style (think RoR for example) and less bug-prone (more secure etc...) because it's well tested by many.
- More powerful than previous concepts but with the same useful properties.
- Or as powerful as the previous concepts but with more useful properties.
One thing that occurs to me is that it relates to what part of a system I identify with. For example, I think very differently about a dictatorship if I imagine myself the benevolent dictator than if I think of myself as a citizen.
I also feel very differently about the different sorts of system depending on what I'm up to. When I'm mainly exploring a problem space, I want powerful tools, but when I'm building something to last, I want something safely constrained. In the former, I place my identity with the lone author, where the power to do the unexpected is vital. In the latter, I identify with those maintaining and debugging a system, where the power to do anything is a giant pain.
What makes these assertions true? Research/data/polls etc would be helpful. It is hard to accept such wide-ranging claims without some proof.
Also, could someone please post the effective definitions of "expressiveness" and "capability" as used in the post ?
Thanks.
Well, the article gave 10 or 20 examples. That's not proof, but it is data...
The interesting bit is that the traditional wisdom in business is "in the end modular approaches to technology always defeat integrated approaches", although how this will play out in Apple's case is hard to predict, because I suppose Apple is kind of special. However if we apply the traditional business wisdom to the software domain here, I wonder the same holds: that the expressive/integrated approach is more powerful initially (where may the modular woudln't be able to get "off the ground"), but over time it looses ground to the constrained/modular approach as the modular benefits are allowed to scale to their full potential.
Today, we have a million different pieces from various sets, and it is difficult to put them together in ways that conform to what we imagine, so they aren't as much fun.
Is this the same idea?