On Tue, 18 Nov 2008 17:12:57 -0500 (EST), beginners-request@haskell.org said:

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Today's Topics:

1. Re: Profiling haskell code (Brent Yorgey) 2. Parsing arithmentic expressions (Glurk) 3. Re: Parsing arithmentic expressions (Bernie Pope) 4. RE: Profiling haskell code (Sayali Kulkarni) 5. Re: Profiling haskell code (Brent Yorgey) 6. Type polymorphism with size (Michael Snoyman) 7. Re: Type polymorphism with size (Brent Yorgey) 8. Re: Type polymorphism with size (Michael Snoyman)

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Message: 1 Date: Fri, 14 Nov 2008 15:53:34 -0500 From: Brent Yorgey Subject: Re: [Haskell-beginners] Profiling haskell code To: beginners@haskell.org Message-ID: <20081114205334.GA30261@seas.upenn.edu> Content-Type: text/plain; charset=us-ascii

...

quicksort [ ] = [ ]

quicksort (x : xs) = quicksort larger ++ [x ] ++ quicksort smaller

where

smaller = [a | a <- xs, a <= x ]

larger = [b | b <- xs, b > x ]

When I compile the code with the following command :

$ ghc --make Project.hs -prof -auto-all

Then I tested it with the following command :

$ Project +RTS -p

It generates the .hi and the .o file but I cannot get the .prof file.

Please let me know if any of the steps is missing or where could I check my profiling info.

Hi Sayali,

Is the code shown above *everything* in your Project.hs file? You will also need a main function for it to actually do anything. If there is more to your Project.hs file that you have not shown, could you send the complete version?

Do you get any errors? Does Project produce the output that you expect?

-Brent

------------------------------

Message: 2 Date: Sun, 16 Nov 2008 00:15:29 +0000 (UTC) From: Glurk Subject: [Haskell-beginners] Parsing arithmentic expressions To: beginners@haskell.org Message-ID: Content-Type: text/plain; charset=us-ascii

Hi,

I'm just trying to learn how to use Parsec and am experimenting with parsing arithmetic expressions.

This article gives a good example -> http://www.haskell.org/haskellwiki/Parsing_expressions_and_statements

However, like most other examples I could find, the grammar for the expression doesn't take operator precedence into account, and allows for expressions of any size by defining expr recursively, eg :-

expr ::= var | const | ( expr ) | unop expr | expr duop expr

So, you can keep extending the expression by adding another operator and expression.

The data to hold the expression is then very easily derived :-

data Expr = Var String | Con Bool | Uno Unop Expr | Duo Duop Expr Expr

The grammar I want to parse is slightly different in that it allows for operator precendence. Part of the grammar is something like :-

expression = SimpleExpression {relation SimpleExpression}. SimpleExpression = ["+"|"-"] term {AddOperator term}.

So, instead of recursively defining expression, it is made up of multiples occurrences of SimpleExpression joined together with Relation operators.

Where I am confused is how I should best represent this stucture in my data. Should I have something like :-

data Expr = Expr SimpleExpr [(RelOp, SimpleExpression)]

ie, an initial SimpleExpr, followed by a list of operator and SimpleExpression pairs.

I haven't seen any example similar to this, so I was wondering if I'm going down the wrong track ?

Perhaps another alternative is to modify the grammar somehow ?

I guess, the question is, in general how do you handle such repeated elements as definied in an EBNF grammar, in structuring your data ?

Any advice appreciated !

Thanks :)

------------------------------

Message: 3 Date: Mon, 17 Nov 2008 16:35:02 +1100 From: Bernie Pope Subject: Re: [Haskell-beginners] Parsing arithmentic expressions To: Glurk Cc: beginners@haskell.org Message-ID: <57383C16-16DD-4032-9CBC-5D6CC27A6E6E@csse.unimelb.edu.au> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes

Hi,

Have you seen the buildExpressionParser combinator in Parsec?

http://legacy.cs.uu.nl/daan/download/parsec/parsec.html#buildExpressionParse...

It allows you to specify precedence and associativity for operator parsers declaratively, and it generally saves you from lots of refactoring in the grammar.

You could probably stick with the straightforward data representation of expressions.

Cheers, Bernie.

On 16/11/2008, at 11:15 AM, Glurk wrote:

...

Hi,

I'm just trying to learn how to use Parsec and am experimenting with parsing arithmetic expressions.

This article gives a good example -> http://www.haskell.org/haskellwiki/Parsing_expressions_and_statements

However, like most other examples I could find, the grammar for the expression doesn't take operator precedence into account, and allows for expressions of any size by defining expr recursively, eg :-

expr ::= var | const | ( expr ) | unop expr | expr duop expr

So, you can keep extending the expression by adding another operator and expression.

The data to hold the expression is then very easily derived :-

data Expr = Var String | Con Bool | Uno Unop Expr | Duo Duop Expr Expr

The grammar I want to parse is slightly different in that it allows for operator precendence. Part of the grammar is something like :-

expression = SimpleExpression {relation SimpleExpression}. SimpleExpression = ["+"|"-"] term {AddOperator term}.

So, instead of recursively defining expression, it is made up of multiples occurrences of SimpleExpression joined together with Relation operators.

Where I am confused is how I should best represent this stucture in my data. Should I have something like :-

data Expr = Expr SimpleExpr [(RelOp, SimpleExpression)]

ie, an initial SimpleExpr, followed by a list of operator and SimpleExpression pairs.

I haven't seen any example similar to this, so I was wondering if I'm going down the wrong track ?

Perhaps another alternative is to modify the grammar somehow ?

I guess, the question is, in general how do you handle such repeated elements as definied in an EBNF grammar, in structuring your data ?

Any advice appreciated !

Thanks :)

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

------------------------------

Message: 4 Date: Mon, 17 Nov 2008 09:35:26 +0530 From: "Sayali Kulkarni" Subject: RE: [Haskell-beginners] Profiling haskell code To: "Brent Yorgey" , Message-ID: <82C3BC9106BCE149B63464D79D0A22FD0761A60E@sohm.kpit.com> Content-Type: text/plain; charset="us-ascii"

Hello Brent,

I just have written a quick sort program. There is nothing more in the code than that I have shown.

What is it about the main function? What do I need to do in the main function?

I do not get any errors. And I get the expected output. The only thing that I am stuck at is that I do not get the ".prof" file which will give me the profile details of the code.

Also it would be great if you could through a light on whether there is any other method to profile a code in Haskell?

Regards, Sayali.

-----Original Message----- From: beginners-bounces@haskell.org [mailto:beginners-bounces@haskell.org] On Behalf Of Brent Yorgey Sent: Saturday, November 15, 2008 2:24 AM To: beginners@haskell.org Subject: Re: [Haskell-beginners] Profiling haskell code

...

quicksort [ ] = [ ]

quicksort (x : xs) = quicksort larger ++ [x ] ++ quicksort smaller

where

smaller = [a | a <- xs, a <= x ]

larger = [b | b <- xs, b > x ]

When I compile the code with the following command :

$ ghc --make Project.hs -prof -auto-all

Then I tested it with the following command :

$ Project +RTS -p

It generates the .hi and the .o file but I cannot get the .prof file.

Please let me know if any of the steps is missing or where could I

check

...

my profiling info.

Hi Sayali,

Is the code shown above *everything* in your Project.hs file? You will also need a main function for it to actually do anything. If there is more to your Project.hs file that you have not shown, could you send the complete version?

Do you get any errors? Does Project produce the output that you expect?

-Brent _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

------------------------------

Message: 5 Date: Mon, 17 Nov 2008 09:07:57 -0500 From: Brent Yorgey Subject: Re: [Haskell-beginners] Profiling haskell code To: beginners@haskell.org Message-ID: <20081117140757.GA13235@seas.upenn.edu> Content-Type: text/plain; charset=us-ascii

On Mon, Nov 17, 2008 at 09:35:26AM +0530, Sayali Kulkarni wrote:

...

Hello Brent,

I just have written a quick sort program. There is nothing more in the code than that I have shown.

What is it about the main function? What do I need to do in the main function?

I do not get any errors. And I get the expected output. The only thing that I am stuck at is that I do not get the ".prof" file which will give me the profile details of the code.

Also it would be great if you could through a light on whether there is any other method to profile a code in Haskell?

Regards, Sayali.

Hi Sayali,

Just writing a quicksort function by itself is fine if you want to test it interactively in ghci. But if you want to profile it you will have to make an executable, which means you will need a 'main' function which says what to do when the program is run. Your main function might look something like this:

main = do print "Sorting..." print (length (quicksort (reverse [1..1000000]))) print "Done!"

Of course, sorting a list in reverse order might not be a very representative task; you might also want to look into the System.Random module to generate a list of a million random elements and sort that.

-Brent

...

-----Original Message----- From: beginners-bounces@haskell.org [mailto:beginners-bounces@haskell.org] On Behalf Of Brent Yorgey Sent: Saturday, November 15, 2008 2:24 AM To: beginners@haskell.org Subject: Re: [Haskell-beginners] Profiling haskell code

...

quicksort [ ] = [ ]

quicksort (x : xs) = quicksort larger ++ [x ] ++ quicksort smaller

where

smaller = [a | a <- xs, a <= x ]

larger = [b | b <- xs, b > x ]

When I compile the code with the following command :

$ ghc --make Project.hs -prof -auto-all

Then I tested it with the following command :

$ Project +RTS -p

It generates the .hi and the .o file but I cannot get the .prof file.

Please let me know if any of the steps is missing or where could I

check

...

my profiling info.

Hi Sayali,

Is the code shown above *everything* in your Project.hs file? You will also need a main function for it to actually do anything. If there is more to your Project.hs file that you have not shown, could you send the complete version?

Do you get any errors? Does Project produce the output that you expect?

-Brent _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

------------------------------

Message: 6 Date: Tue, 18 Nov 2008 10:02:20 -0800 From: "Michael Snoyman" Subject: [Haskell-beginners] Type polymorphism with size To: beginners@haskell.org Message-ID: <29bf512f0811181002k7ea715f3o8d797aae6a4b3855@mail.gmail.com> Content-Type: text/plain; charset="utf-8"

I am trying to write some code to read flat files from a mainframe system. This includes some character fields. This is a fixed width file, so each field will have a consistent length between records, but there are fields of different length within a record. For example, I might have a "name" field length 20 and an eye color field length 5.

I am trying to use the binary library to read in this file. I've written a binary type, MFChar2, for reading in a 2-length character field. It is defined as such (you can safely ignore the ebcdicToAscii piece, it is just doing character conversion):

data MFChar2 = MFChar2 [Word8] instance Binary MFChar2 where put = undefined get = do ebcdic <- replicateM 2 getWord8 return $ MFChar2 $ map ebcdicToAscii ebcdic

What I would like to do is have some kind of generic "MFChar" data type which could take any character length, but I can't figure out how to do it. Any help would be appreciated.

Thanks, Michael