Re: [Haskell-cafe] About code style ?
thanks for all suggestions.
zaxis wrote:
For me i like C style instead of layout. For example,
func1 a = do
-- ...
a * 2
-- ...
I always write it as:
func1 a = do {
-- ...;
a * 2;
-- ...;
}
However, i donot know how to write pure function using C style.
func1 a = {
-- ...;
a * 2;
-- ...;
}
will not compile without `do`.
Sincerely!
-
fac n = foldr (*) 1 [1..n]
--
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Re: [Haskell-cafe] About code style ?
fac n = let {
f = foldr (*) 1 [1..n]
} in f
:D
sorry for double reply, need to cc cafe, this is fun.
On Tue, Feb 2, 2010 at 4:33 PM, zaxis z_a...@163.com wrote:
thanks for all suggestions.
zaxis wrote:
For me i like C style instead of layout. For example,
func1 a = do
-- ...
a * 2
-- ...
I always write it as:
func1 a = do {
-- ...;
a * 2;
-- ...;
}
However, i donot know how to write pure function using C style.
func1 a = {
-- ...;
a * 2;
-- ...;
}
will not compile without `do`.
Sincerely!
-
fac n = foldr (*) 1 [1..n]
--
View this message in context:
http://old.nabble.com/About-code-style---tp27414627p27416932.html
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jinjing
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RE: [Haskell-cafe] About code style ?
From: haskell-cafe-boun...@haskell.org
[mailto:haskell-cafe-boun...@haskell.org] On Behalf Of zaxis
For me i like C style instead of layout. For example,
func1 a = do {
-- ...;
a * 2;
-- ...;
}
The report has all the gory details. The brace+semicolon syntax isn't
just for do-blocks; it can be used anywhere that indenting is used to
specify scope.
Section 2.7:
http://www.haskell.org/onlinereport/lexemes.html#lexemes-layout
Section 9.3:
http://www.haskell.org/onlinereport/syntax-iso.html#layout
Alistair
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Re: [Haskell-cafe] About code style ?
fac n = let { f = foldr (*) 1 [1..n] } in f
VERY interesting :)
Jinjing Wang wrote:
fac n = let {
f = foldr (*) 1 [1..n]
} in f
:D
sorry for double reply, need to cc cafe, this is fun.
On Tue, Feb 2, 2010 at 4:33 PM, zaxis z_a...@163.com wrote:
thanks for all suggestions.
zaxis wrote:
For me i like C style instead of layout. For example,
func1 a = do
-- ...
a * 2
-- ...
I always write it as:
func1 a = do {
-- ...;
a * 2;
-- ...;
}
However, i donot know how to write pure function using C style.
func1 a = {
-- ...;
a * 2;
-- ...;
}
will not compile without `do`.
Sincerely!
-
fac n = foldr (*) 1 [1..n]
--
View this message in context:
http://old.nabble.com/About-code-style---tp27414627p27416932.html
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fac n = foldr (*) 1 [1..n]
--
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[Haskell-cafe] About code style ?
For me i like C style instead of layout. For example,
func1 a = do
-- ...
a * 2
-- ...
I always write it as:
func1 a = do {
-- ...;
a * 2;
-- ...;
}
However, i donot know how to write pure function using C style.
func1 a = {
-- ...;
a * 2;
-- ...;
}
will not compile without `do`.
Sincerely!
-
fac n = foldr (*) 1 [1..n]
--
View this message in context:
http://old.nabble.com/About-code-style---tp27414627p27414627.html
Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.
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Re: [Haskell-cafe] About code style ?
zaxis z_a...@163.com writes:
However, i donot know how to write pure function using C style.
func1 a = {
-- ...;
a * 2;
-- ...;
}
You mean imperatively? Short answer: you can't and you shouldn't.
Slightly longer answer: you can possibly fudge something together using
the Identity monad from mtl, but that will involve wrapping/unwrapping
everywhere.
Learn to think about how to chain/group functions together to form more
of a pipeline rather than a sequence of statements. Haskell =/= C.
--
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] About code style ?
zaxis wrote:
For me i like C style instead of layout. For example,
func1 a = do
-- ...
a * 2
-- ...
I always write it as:
func1 a = do {
-- ...;
a * 2;
-- ...;
}
Honestly, don't do this.
When you're coding in Haskell you should write idiomatic Haskell and when
doing C, do idiomatic C.
Inventing your own coding style for a language will make it difficult for
other people who know and use that language to read your code and sooner
or later you will want to or need to work with others.
Erik
--
--
Erik de Castro Lopo
http://www.mega-nerd.com/
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Re: [Haskell-cafe] About code style ?
However, i donot know how to write pure function using C style.
func1 a = {
-- ...;
a * 2;
-- ...;
}
What do you mean by a * 2? If you don't use this value, don't
calculate it.
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Re: [Haskell-cafe] About code style ?
Ditto what everyone else has said. But to clarify what's going on:
The braces are used to introduce a list of things, such as monadic actions,
data fields, or declarations. For example, consider the following code:
f a =
let {
a_times_2 = a*2;
a_times_4 = a*4;
} in a_times_2+a_times_4
main = putStrLn $ f 3 = ++ show (f 3)
The reason why my code compiled and yours didn't is because the compiler saw
that the braces were being used to introduce a list of declarations, and the
reason why it knew this was because of the let keyword. By contrast, in your
code it doesn't see a let, so it assumes that you must be introducing a list
of monadic actions. Hence it yells at you for not putting in a do.
Remember that a pure function is merely a definition of what the output is for
a given input. It does not say anything about *how* to do this. Thus, you
should never think of a pure function as being a list of actions but rather
(approximately) a definition which may require some additional declarations
(such as introduced by let) solely for the purpose of making it easier for
*you* to *express* what its value is. (I say approximately because the way you
express it does affect the way it gets computed despite technically being pure,
but this is not something you should be worrying about right now.)
But again, even though you could use curly brackets and semicolons as I
illustrated above, you really should be using whitespace as it is the standard
practice; others reading your code may be confused by their presence and so
have to work harder to figure out what is going on.
Cheers,
Greg
On Feb 1, 2010, at 6:22 PM, zaxis wrote:
For me i like C style instead of layout. For example,
func1 a = do
-- ...
a * 2
-- ...
I always write it as:
func1 a = do {
-- ...;
a * 2;
-- ...;
}
However, i donot know how to write pure function using C style.
func1 a = {
-- ...;
a * 2;
-- ...;
}
will not compile without `do`.
Sincerely!
-
fac n = foldr (*) 1 [1..n]
--
View this message in context:
http://old.nabble.com/About-code-style---tp27414627p27414627.html
Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.
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