[andrewcooke]

i think you can make the case that for many (largely self-educated) programmers, learning new languages is a good way to understand programming at a more abstract level. and that, in turn, means that you can write better code.

for example, if you understand an object-oriented and a functional language then you understand two quite different ways of encapsulating state - as objects and as closures. that leads you to thinking about state as something more general than either, which gives you a higher level view of the problems you are tackling.

so learning multiple languages illustrates different aspects of "deeper" issues in programming and motivates the discovery of those abstract concepts, which then provide a stronger "mental toolbox" to do your work.

from my own work, for example, i feel that google's guava library has improved my java code considerably. using that library well requires (i believe) an understanding of the advantages and disadvantages of both oo and fp programming.

[loup-vaillant]

> if you understand an object-oriented and a functional language then you understand two quite different ways of encapsulating state - as objects and as closures. that leads you to thinking about state as something more general than either, which gives you a higher level view of the problems you are tackling.

Yet, it may not be general enough. With one data point, one doesn't generalize. With two, one tends to think of a spectrum. With three… Now it gets interesting.

For instance, encapsulating state: you had objects and closures. They look pretty different, until you learn of Functional Reactive Programming, where state is handled in a much more timeless fashion.