Is it better to focus on one path, avoiding contamination from others?
Learning multiple programming languages will broaden your perspective and will make you a better and more flexible programmer over time.
Is it better to explore several simultaneously, to make sure you don't miss the best parts?
If you are new and learning on your own, you should focus on one language at a time. Pick a project to work on and then pick the language you are going to use. I like to code a Mandelbrot set image generator in each language I learn.
Which one results in converting time to dollars the most quickly?
If you make your dollars only from the finished product, then pick the language with the highest productivity for your target platform and problem domain. This will probably be a garbage collecting language with a clean syntax, with a good integrated development environment, and with a large available set of libraries.
Right now this will probably be Python, Java or C#.
If you make your dollars by producing lines of code for a company, then you will want to learn a language that is heavily used. There is generally a large demand for C++, C#, Java, Python, and PHP programmers. Companies in certain domains will focus on other languages like Lisp, Smalltalk and Ada.
Which one most reliably converts you to a higher value programmer over a longer period of time?
No single language will do this in the long run, but you might take temporary advantage of the current rise of Python, or the large install base of Java and C++.
For a broad basic education I suggest:
If you want to do web-related development:
If you want to do engineering related development:
Learn an assembly language. Your platform of choice.
One way to do this is by writing small C programs and looking at the assembler a compiler generates e.g. by calling gcc with -S. (You can also use this to get some understanding of the optimisations a compiler performs by comparing the difference between the assembler with optimisations and the assembler with full optimisations.)
As you do this, you should also start replacing bits of the C code with inline assembler that you have written yourself, since writing code is better than just reading code.
(Al...
Learning to program in a given language requires a non-trivial amount of time. This seems to be agreed upon as a good use of LessWrongers' time.
Each language may be more useful than others for particular purposes. However, like e.g. the choice of donation to a particular charity, we shouldn't expect the trade-offs of focusing on one versus another not to exist.
Suppose I know nothing about programming... And I want to make a choice about what language to pick up beyond merely what sounds cool at the time. In short I would want to spend my five minutes on the problem before jumping to a solution.
As an example of the dilemma, if I spend my time learning Scheme or Lisp, I will gain a particular kind of skill. It won't be a very directly marketable one, but it could (in theory) make me a better programmer. "Code as lists" is a powerful perspective -- and Eric S. Raymond recommends learning Lisp for this reason.
Forth (or any similar concatenative language) presents a different yet similarly powerful perspective, one which encourages extreme factorization and use of small well-considered definitions of words for frequently reused concepts.
Python encourages object oriented thinking and explicit declaration. Ruby is object oriented and complexity-hiding to the point of being almost magical.
C teaches functions and varying abstraction levels. Javascript is more about the high level abstractions.
If a newbie programmer focuses on any of these they will come out of it a different kind of programmer. If a competent programmer avoids one of these things they will avoid different kinds of costs as well as different kinds of benefits.
Is it better to focus on one path, avoiding contamination from others?
Is it better to explore several simultaneously, to make sure you don't miss the best parts?
Which one results in converting time to dollars the most quickly?
Which one most reliably converts you to a higher value programmer over a longer period of time?
What other caveats are there?