Re: [Haskell-cafe] 2 modules in one file
Maurício [EMAIL PROTECTED] wrote: Is it allowed to write two different modules in a single file? Some compilers permit it (e.g. Freja), most do not (e.g. ghc). The Language Report makes no specification for the mapping between module sources and the files that contain them. Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] 2 modules in one file
Maurício wrote: Is it allowed to write two different modules in a single file? That would be a really nice feature, especially since modules are Haskell's only encapsulation tool. You want it to be a lightweight as possible. Malcolm Wallace wrote: Some compilers permit it (e.g. Freja), most do not (e.g. ghc). The Language Report makes no specification for the mapping between module sources and the files that contain them. The Hierarchical Module Namespace Extension addendum to the Haskell 98 Report http://www.haskell.org/hierarchical-modules/ recommends, but does not require, a Java-like mapping between hierarchical module names and and the filesystem. In particular, compilers complying with that recommendation require there to be only one module per file. Most compilers do comply. In my opinion, that is a bad policy. It is fine as a simple default for small projects, even though it's a bit ugly and ad hoc. (For example - what does this mean on platforms whose filesystem is not hierarchical?) But for large and complex projects, this policy really complicates the task of the project manager who wants to be able to present various views of the source to teams working on different subprojects, while juggling the version control in an intelligent way. Directory tree structure is sometimes the perfect tool for that, but Haskell has stolen it away. It would be nice if compilers would offer, as an optional alternative, a system of locating modules based on manifest files. That would then allow multiple modules per source file. Regards, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] 2 modules in one file
Hi, Yitzchak Gale wrote: But for large and complex projects, this policy really complicates the task of the project manager who wants to be able to present various views of the source to teams working on different subprojects, while juggling the version control in an intelligent way. Directory tree structure is sometimes the perfect tool for that, but Haskell has stolen it away. It would be nice if compilers would offer, as an optional alternative, a system of locating modules based on manifest files. That would then allow multiple modules per source file. Not that it is of any practical relevance now, but this was exactly the thinking behind the design (some 10 - 15 years ago, time flies!) of how Freja manages files and modules, as Malcolm mentioned. I believe a clear separation between a language and aspects of the environment in which programs are developed, such as file systems, is a good thing. And while the Haskell standard as such respects this, I've always found the fact that most tools rely on naming conventions for mapping names of modules to names of files very unfortunate. Hierarchical modules makes this even worse: what says that I necessarily want the module hierarchy reflected in the directory hierarchy? And indeed, as Yitzchak said, what about non-hierarchical file systems, or maybe storing source code by completely different means? And there are also potential issues with not every legal module name being a legal file name across all possible file systems. So, yes, a system of locating modules based on manifest files would be great. I'd use it all the time whenever possible, and never look back! Best, /Henrik -- Henrik Nilsson School of Computer Science The University of Nottingham [EMAIL PROTECTED] This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] 2 modules in one file
I have submitted this as Feature Request #2550 http://hackage.haskell.org/trac/ghc/ticket/2550 Please add any comments as appropriate. Thanks, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] 2 modules in one file
Is it allowed to write two
different modules in a single
file? Something like:
module Mod1 (...) where {
...
}
module Mod2 (...) where {
import Mod1;
...
}
I tried, and got an error,
but would like to confirm
that there's no way to do
that.
No, that's not possible because haskell will use the module name A.B.C
to look the module up in path A/B/C.[l]hs.
So using modules
module A where
..
module B where
the compiler could only find one of them. (naming the file A.hs or B.hs)
You have to use one file for each module
I think there is another tool somewhere to merge many modules into one.
But I don't think that's what you're looking for. (I haven't tried that
myself)
Marc Weber
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[Haskell-cafe] 2 modules in one file
Hi,
Is it allowed to write two
different modules in a single
file? Something like:
module Mod1 (...) where {
...
}
module Mod2 (...) where {
import Mod1;
...
}
I tried, and got an error,
but would like to confirm
that there's no way to do
that.
Thanks,
Maurício
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