Brian Hulley wrote:
Consider the scenario when you want to find a function that returns the i'th element of an array but all you know is that there is a module called Data.Array.IArray that will probably have such a function in it. So you start typing in your program:
let ith = Data.Array.IArray.
at this point, you'd hope the editor you're using would somehow display a list of avaliable values exported from Data.Array.IArray including the indexing function, so you could select it, thus I would *like* to be able to use the syntax:
let ith = Data.Array.IArray.(!)
because it's not the user's fault that the person who wrote Data.Array.IArray decided to use a symbol instead of an identifier for this function - the user of Data.Array.IArray in this case just wants to see normal identifiers to use with prefix application so the use of (!) at this point effectively gets rid of the unwanted operatorness associated with the function.
However the current syntax of Haskell would not allow this. Instead you have to write:
let ith = (Data.Array.IArray.!)
The problem is that the user of Data.Array.IArray has to know already in advance, before typing the 'D' of "Data", that the indexing function has been named with a symbol instead of an identifier, but this knowledge is only available later, when the user has typed the '.' after "IArray", so the current syntax would be frustrating for the user because the user then has to go all the way back and insert an opening paren before the 'D'.
Sorry, but I can't see the problem here. Why can't the editor offer the operator as '!' in the list of options, and if the user selects it insert both '(' and ')' at the right places (i.e. before the module name and after the operator)? Is there some unwritten law that forbids editors or IDEs to insert stuff at positions other than the current cursor position? Isn't Haskell (assuming you are programming your editor in Haskell) not supposed to make hard things easy(er)? Rather than complain about libraries that offer operators (which i personally like very much, thank you) or proposing to change the language, use your imagination and design a new human interface that deals with the language in the most useful way. [BTW, I recommend you take a look at what Conor BcBride did to support 'visual' (dependently typed) programming in Epigram. There's many good ideas there to steal from ;)] Generally speaking, I would always hesitate to change the language so it better suits programming tools(*). It is the tools which should adapt to the language, even if that means the programmer has to find new ways of suporting the user (and the language). The most important reason being that code is more often read than written. That said, there still might be good arguments to change the syntax in the way you propose, just not the one you gave above. In fact, I am half of a mind to say I like Data.Array.IArray.(!) better than (Data.Array.IArray.!). My reason is that the former is more readable because it highlights the operator symbol by surrounding it with parentheses, whereas the latter obscures it. At the danger of becoming completely off-topic now (sorry!), I have to say that I find /both/ versions ugly and unnecessarily hard to read. My personal solution is to generally avoid qualified imports. I use it only if absolutely necessary to disambiguate some symbol, and then just for that symbol. I am aware that there is an opposing faction here, who tries to convinve everyone that qualified import should be the standard (and the actual exported symbols --at least some of them-- meaningless, such as 'C' or 'T'). I think such a convention is inappropriate for a functional language (especially one with user defined operators). There simply is no natural 1:1 correspondence between data type declaration and functions acting on that data built into the language, as opposed to e.g. OO languages. Extensibility in the functional dimension, i.e. the ability to arbitrarily add functions that operate on some data without having to change the code (module) that defines the data, is one of the hallmarks of functional programming, as opposed to OO programming.(**) Cheers Ben -- (*) Yes I know it has at least to be compilable, preferably in an efficient way. However, that doesn't invalidate the argument. Indeed, it is bad enough that we have to compromise in order to make our languages implementable with current compiler technology. No need to compromise on much less essential equipment, such as syntax aware editing tools. (**) One could argue that this extensibility is lost anyway as soon as /abstract/ data types come into play. However, [warning: it gets even more off-topic from here on] nothing prevents us from offering /two/ interfaces (visible modules), one where the data type is abstract ("client interface") and a different one where it is concrete ("extension interface"). Of course, only the abstract (client) interface guarantees that invariants cannot be broken by the user code. But that doesn't mean a concrete interface wouldn't be useful. How often have there been requests to add this or that function to some standard library abstract data type? If the concrete type would be available via an extension interface, users who need additional functions that operate directly on the underlying data structure (for instance for efficiency reasons) could then build and also publish such extension modules (with, again, an abstract interface so usage is safe). [I am aware that this can lead to maintenance problems if the internal data type or invariants get changed. I still think it is better to have the possibility to add new functions (and live with eventual consequences) than to not have it.]