On Thu, Apr 9, 2015 at 5:40 PM, Peng Yu pengyu...@gmail.com wrote:
However, the real problem is that global variable make larger programs
difficult to maintain. Therefore, the problem becomes severe for
people using bash for making bash libraries. Any ad hoc use of bash
can always get away from this problem.
The solution is namespaces. ksh93 supports namespace blocks (including nested
namespaces), though it's still quite buggy.
Note C doesn't have namespaces either and gets by despite being used as
a library language to a much greater extent than bash. It's worked around with
naming conventions. There are many prefix conventions even within the
C standard library and POSIX for various headers - atomic_*, mtx_*, pthread_*,
sem_*, etc.
On Fri, Apr 10, 2015 at 8:54 AM, Peng Yu pengyu...@gmail.com wrote:
You don't know functional programming, do you? That example is
functional program (not full fledged though) but not OO.
It seems that you don't know its importance, either? With functional
programming, you basically can make OO on top of it, but not the other
way around. R has examples on how to make OO using functional
programing.
Functional programming is a style, not a language feature. Features that
facilitate it are common in OO langs.
C# implements first-class functions with closures by translating them in the IL
to inner classes that maintain the lexical state. I'm pretty sure Java 8 does
essentially the same with its lambdas. People have been using the inner class
trick for ages prior to that.
function as first class citizen is just one of the feature that makes
javascript so successful now days.
The type of function you're talking about isn't merely a local function.
JavaScript doesn't exactly have local functions, and probably isn't the best
example because of its numerous ways of defining functions. It also doesn't
have a separate namespace for functions. No matter how you define them, you're
likely using sugar that in the end results in a function object that's
accessed through an identifier that's in the same namespace as any other
variable (which might be local).
Bash needs several major features before it could even think about supporting
function objects.
First it needs yet another type of function (probably with yet another syntax)
which supports returning a value, and declaration as an expression so it can
be passed around and treated as a value.
At the same time it needs to add some sort of type system so that data other
than strings (objects or functions) can be bound to variables and formal
parameters.
ksh93 has the beginnings of an object system which supports user-defined types,
but functions are still insufficient for doing anything functional. Some of
its basic ideas are nice but I have pretty much given up on understanding David
Korn's design. It's obviously half-baked in its current state and hard to use
for getting real work done. It's better than nothing I guess.
Anyway, you can probably do something resembling FP with some combination of
`typeset -T` wrappers to contain your functions, and `typeset -M` and `-C` to
move and copy objects around by reference. It's not pretty.
--
Dan Douglas
