[Haskell-cafe] How to use "bracket" properly ?

zaxis z_axis at 163.com
Mon Oct 19 07:44:30 EDT 2009


oh! thanks!  But why ?


Heinrich Apfelmus wrote:
> 
> zaxis wrote:
>> It works very well. However, as i am used to C style so i want convert it
>> into
>> 
>> winSSQ count noRed noBlue = do {
>>     let yesRed =  [1..33] \\ noRed;
>>     let yesBlue = [1..16] \\ noBlue;
>>     bracket (openFile "ssqNum.txt" WriteMode) (hClose) (\hd1 -> pickSSQ
>> count yesRed yesBlue hd1);
>> } 
> 
> You need to put brackets around the declarations in a  let  as well:
> 
>     winSSQ count noRed noBlue = do {
>         let { yesRed =  [1..33] \\ noRed  };
>         let { yesBlue = [1..16] \\ noBlue };
>         bracket (openFile "ssqNum.txt" WriteMode) (hClose)
>                 (\hd1 -> pickSSQ count yesRed yesBlue hd1);
>     }
> 
> 
> Regards,
> apfelmus
> 
> --
> http://apfelmus.nfshost.com
> 
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