Re: [Haskell-cafe] Layout rule (was Re: PrefixMap: code review request)
On 28/02/06, Brian Hulley [EMAIL PROTECTED] wrote: Why? Surely typing one tab is better than having to hit the spacebar 4 (or 8) times? I'm really puzled here. I've been using tabs to indent my C++ code for at least 10 years and don't see the problem. The only problem would be if someone mixed tabs with spaces. Since it has to be either tabs only or spaces only I'd choose tabs only to save keystrokes. I suppose though it is always going to be a matter of personal taste... It's easy to configure most editors (vim and emacs included of course) to treat multiple spaces as if they were tabs, but to only save spaces into your file. This is what I do, as it ensures that the way that the code looks to me in my editor is exactly what it looks like to the compiler. Quite often, if it looks better, I will align things past a tab stop with a few extra spaces (which only has to be done once, if your editor will start the next line at the same indentation as the previous). - Cale ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Layout rule (was Re: PrefixMap: code review request)
On Wednesday 01 March 2006 02:36, Brian Hulley wrote:
Ben Rudiak-Gould wrote:
Brian Hulley wrote:
Here is my proposed layout rule:
1) All layout keywords (where, of, let, do) must either be
followed by a single element of the corresponding block type, and
explicit block introduced by '{', or a layout block whose first
line starts on the *next* line
I wouldn't have much trouble adapting to that.
and whose indentation is accomplished *only* by tabs
You can't be serious. This would cause far more problems than the
current rule.
Why? Surely typing one tab is better than having to hit the spacebar
4 (or 8) times?
What kind of editor are you using? Notepad?
I am used to hitting TAB key and get the correct number of spaces,
according to how I configured my editor (NEdit) for the current
language mode.
TAB characters in program text should be forbidden by law. As well as
editors that by default insert a tab char instead of spaces.
Ben
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Re: [Haskell-cafe] Layout rule (was Re: PrefixMap: code review request)
Am Mittwoch, 1. März 2006 11:57 schrieb Benjamin Franksen: TAB characters in program text should be forbidden by law. As well as editors that by default insert a tab char instead of spaces. As founding member of the church of The only good Tabbing involves Michaela, I wholeheartedly agree. Cheers, Daniel -- In My Egotistical Opinion, most people's C programs should be indented six feet downward and covered with dirt. -- Blair P. Houghton ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Layout rule (was Re: PrefixMap: code review request)
Brian Hulley wrote:
Here is my proposed layout rule:
1) All layout keywords (where, of, let, do) must either be followed by a
single element of the corresponding block type, and explicit block
introduced by '{', or a layout block whose first line starts on the
*next* line
I wouldn't have much trouble adapting to that.
and whose indentation is accomplished *only* by tabs
You can't be serious. This would cause far more problems than the current rule.
I would also make it that explicit braces are not allowed to switch off
the layout rule (ie they can be used within a layout),
I don't understand. What does used within a layout mean?
multiline strings would not be permitted,
They aren't now, except with \ escapes. A stray will be caught on the same
line unless the line happens to end with \ and the next line happens to
begin with \, which is exceedingly unusual.
and multiline comments would not be permitted
(pragmas could easily be used just by using --#)
But --# doesn't introduce a comment. And this would make UNPACK pragmas
rather inconvenient to use.
1) When you see a ';' you could immediately tell which block it belongs
to by looking backwards till the next '{'
I guess that might be helpful, but it doesn't seem easier than looking left
to the beginning of the current line and then up to the first less-indented
line.
2) Variable width fonts can be used,
They can be used now, if you adhere to a certain style, but not everyone
likes that style. I wrote in C++ with a variable width font and tabs at one
time, but eventually went back to fixed width. One reason was that I
couldn't use comment layout conventions that tend (in my experience) to
improve readability more than monospacing hurts it. Another reason was that
glyph widths appropriate to natural languages didn't work all that well for
source code. Spaces are much more important in source code than in natural
language, for example. A proportional font designed for source code would be
nice, but I haven't found one yet. Stroustrup used a mixture of proportional
and monospaced glyphs in _The C++ Programming Language_ and it worked well.
or different font faces to
represent different sorts of identifier eg class names, tycons, value
constructors, operators like `seq` as opposed to seq etc
Lots of editors do this with monospaced fonts; I think it's orthogonal to
the layout issue.
3) Using only tabs ensures that vertical alignment goes to the same
position on the screen regardless of the font and tabs could even have
different widths just like in a wordprocessor
Requiring tabs is a really bad idea. Just forget it. Seriously.
4) Any keypress has a localised effect on the parse tree of the buffer
as a whole ( { no longer kill everything which follows and there would
be no {- )
I don't understand why this is an advantage. If you have an editor that
highlights comments in green, then large sections of the program will flash
green while you type a {- -} comment, which might be annoying, but it also
means you'll never forget to close the comment, so the practical benefit of
forbidding {- -}, as opposed to simply not typing it yourself, seems nil.
5) It paves the way for a much more immersive editing environment, but I
can't say more about this at the moment because I haven't finished
writing it yet and it will be a commercial product :-)))
I guess everything has been leading up to this, but my reaction is that it
renders the whole debate irrelevant. The only reason layout exists in the
first place is to make source code look good in ordinary text editors. If
you have a high-level source code editor that manipulates the AST, then you
don't need layout, or tabs, or any of that silly ASCII stuff. The only time
you need to worry about layout is when interoperating with implementations
that use the concrete syntax, and then there's nothing to stop you from
exporting in any style you like. And when importing, there's no reason to
place restrictions on Haskell's layout rule, because the visual layout you
display in the editor need have no connection to the layout of the imported
file.
Using my self-imposed layout rule I'm currently editing all my Haskell
code in a standard text editor using tabs set to 4 spaces and a variable
width font and have no problems.
Which is the best argument for keeping the current rule! If it were changed
as you propose, then someday Hugh Briley would come along and complain that
Haskell's layout syntax squandered screen space---but he *wouldn't* be able
to program in his preferred style, because it would no longer be allowed.
Religious freedom is a good thing.
{- Ben -}
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Re: [Haskell-cafe] Layout rule (was Re: PrefixMap: code review request)
Ben Rudiak-Gould wrote:
Brian Hulley wrote:
Here is my proposed layout rule:
1) All layout keywords (where, of, let, do) must either be followed
by a single element of the corresponding block type, and explicit
block introduced by '{', or a layout block whose first line starts
on the *next* line
I wouldn't have much trouble adapting to that.
and whose indentation is accomplished *only* by tabs
You can't be serious. This would cause far more problems than the
current rule.
Why? Surely typing one tab is better than having to hit the spacebar 4 (or
8) times?
I would also make it that explicit braces are not allowed to switch
off the layout rule (ie they can be used within a layout),
I don't understand. What does used within a layout mean?
I meant that {;} would be used just like any other construct that has to
respect the layout rule so you could write
let
a = let { b = 6; z = 77;
h = 99;
p = 100} in b+z+h + p
etc but not:
let
a = let { b = 6; z = 77;
h = 99; -- this binding would be part of the outermost
'let'
p = 100} in b+z+h + p
multiline strings would not be permitted,
They aren't now, except with \ escapes. A stray will be caught on
the same line unless the line happens to end with \ and the next line
happens to begin with \, which is exceedingly unusual.
and multiline comments would not be permitted
(pragmas could easily be used just by using --#)
But --# doesn't introduce a comment. And this would make UNPACK
pragmas rather inconvenient to use.
-- # but I hadn't thought about UNPACK...
The motivation in both points is to make it easy for an editor to determine
which lines need to be re-parsed based on the number of leading tabs alone.
1) When you see a ';' you could immediately tell which block it
belongs to by looking backwards till the next '{'
I guess that might be helpful, but it doesn't seem easier than
looking left to the beginning of the current line and then up to the first
less-indented line.
There was an example posted on another thread where someone had got into
confusion by using ; after a let binding in a do construct with an explicit
brace after the 'do' but not after the 'let' (sorry I can't find it again).
Also the current layout rule uses the notion of an implicit opening brace
which is a to be regarded as a real opening brace as far as ';' in concerned
but an unreal non-existent opening brace as far as '}' is concerned. Thus I
think it is a real mix-up.
2) Variable width fonts can be used,
They can be used now, if you adhere to a certain style, but not
everyone likes that style. I wrote in C++ with a variable width font and
tabs
at one time, but eventually went back to fixed width. One reason was
that I couldn't use comment layout conventions that tend (in my
experience)
to improve readability more than monospacing hurts it. Another reason
was that glyph widths appropriate to natural languages didn't work
all that well for source code. Spaces are much more important in
source code than in natural language, for example. A proportional
font designed for source code would be nice, but I haven't found one
yet. Stroustrup used a mixture of proportional and monospaced glyphs
in _The C++ Programming Language_ and it worked well.
or different font faces to
represent different sorts of identifier eg class names, tycons, value
constructors, operators like `seq` as opposed to seq etc
Lots of editors do this with monospaced fonts; I think it's
orthogonal to the layout issue.
For example on Windows Trebuchet MS is a very nice font, also Verdana, both
of which are not monospaced. But yes I agree it's not a major issue and I
just see the option of being able to use them as a nice side-effect.
3) Using only tabs ensures that vertical alignment goes to the same
position on the screen regardless of the font and tabs could even
have different widths just like in a wordprocessor
Requiring tabs is a really bad idea. Just forget it. Seriously.
I'm really puzled here. I've been using tabs to indent my C++ code for at
least 10 years and don't see the problem. The only problem would be if
someone mixed tabs with spaces. Since it has to be either tabs only or
spaces only I'd choose tabs only to save keystrokes. I suppose though it is
always going to be a matter of personal taste...
4) Any keypress has a localised effect on the parse tree of the
buffer as a whole ( { no longer kill everything which follows and
there would be no {- )
I don't understand why this is an advantage. If you have an editor
that highlights comments in green, then large sections of the program
will flash green while you type a {- -} comment, which might be
annoying, but it also means you'll never forget to close the comment,
so the practical benefit of forbidding {- -}, as opposed to simply
not typing it yourself,
Re: [Haskell-cafe] Layout rule (was Re: PrefixMap: code review request)
On Wed, 1 Mar 2006, Brian Hulley wrote: Ben Rudiak-Gould wrote: Brian Hulley wrote: Here is my proposed layout rule: snip and whose indentation is accomplished *only* by tabs You can't be serious. This would cause far more problems than the current rule. Why? Surely typing one tab is better than having to hit the spacebar 4 (or 8) times? Not when it prevents me from ever exhibiting the slightest shred of style in my code. I use that control for readability purposes in my code. -- [EMAIL PROTECTED] My religion says so explains your beliefs. But it doesn't explain why I should hold them as well, let alone be restricted by them. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Layout rule (was Re: PrefixMap: code review request)
BH Why? Surely typing one tab is better than having to hit the spacebar 4 (or 8) BH times? PC Not when it prevents me from ever exhibiting the slightest shred of style PC in my code. I use that control for readability purposes in my code. [snip] BH I'm really puzled here. I've been using tabs to indent my C++ code for at BH least 10 years and don't see the problem. At least two reasons: 1. C++ doesn't care about any whitespace (except to separate tokens). Haskell cares about leading whitespace (which it is clear you are thinking a lot about...) but 2. as Philippa mentioned, Haskell programmers care a ton about inter-line, inter-word layout/alignment, for example, lining up = signs and arguments to functions in pattern matches, etc. C++ does not invite this style of declarative programming so it is not surprising that it wasn't an issue: aside from the indentation, I rarely type fancy whitespace inside a giving line of C++ code to align elements with those on a preceding line. In Haskell, this unofficial layout style doesn't affect the machine-parsing of the code, but rather the human-parsing of the code. (In fact, it's one of my favorite things about Haskell.) If you want to see what can be accomplished with variable width fonts and complex layouts (not just beginning of lines but rather inter-line, inter-word alignment) you should checkout lhs2TeX. They accomplish all their magic with spaces. BH The only problem would be if BH someone mixed tabs with spaces. Since it has to be either tabs only or BH spaces only I'd choose tabs only to save keystrokes. BTW, tab doesn't type the tab character (at least in emacs and I think vim) but instead moves the left edge of the current line by adding or deleted spaces (or trying to ident the right amount). This usually means you don't have to type 4 or 8 spaces. (And anyway, I would just hold the key down if I had to type more than one spacebar, etc.) [snip] For example on Windows Trebuchet MS is a very nice font, also Verdana, both of which are not monospaced. But yes I agree it's not a major issue and I just see the option of being able to use them as a nice side-effect. Very few programmers I know would go to variable width fonts just to use some Microsoft font to edit code... (BTW I like Trebuchet and Verdana too.) To each his/her own! Cheers, Jared. -- http://www.updike.org/~jared/ reverse )-: ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
