Auto generated instance codes through 'deriving'
Jong Keun Na
jongkn@microsoft.com
Mon, 10 Feb 2003 11:48:10 +0900
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The following code snippet not works correctly.
=20
>data Obj =3D Obj {_id, p1, p2::Int} deriving (Show, Read)
=20
>showObj :: Obj -> String
>showObj o =3D show o
=20
>main =3D do print (showObj (read "Obj {_id=3D1,p1=3D10,p2=3D20}"))
> return ()
=20
The reason is because I used the property name with underscore char like
"_id".
Looking into auto generated class codes and seeing they show it should
encompass identifiers with special characters with parenthesis, so I
tried "Obj {(_id)=3D1,p1=3D10,p2=3D20}" as argument of read func. But, =
the
result is same, parse error.
=20
Is this problem by-design or bug? Or Am I missing any point?
=20
Thanks,
/JongKeun
=20
=20
-----Original Message-----
From: Simon Peyton-Jones=20
Sent: Friday, February 07, 2003 5:41 PM
To: Jong Keun Na; haskell-cafe@haskell.org
Subject: RE: Auto generated instance codes through 'deriving'
=20
Try -ddump-deriv
=20
http://haskell.cs.yale.edu/ghc/docs/latest/html/users_guide/options-debu
gging.html#DUMPING-OUTPUT
=20
Simon
=20
-----Original Message-----
From: Jong Keun Na [mailto:jongkn@microsoft.com]=20
Sent: 07 February 2003 06:15
To: haskell-cafe@haskell.org
Subject: Auto generated instance codes through 'deriving'
=20
Hello folks,
Is there any method with which I can see instance's codes generated
automatically by using 'deriving' keyword in GHC?
I'm curious in how GHC generates 'Read' class's instance code for
user-defined data type.
Any help will be great appreciated.
/JongKeun
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<title>Auto generated instance codes through 'deriving'</title>
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<div class=3DSection1>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'><!-- Converted =
from text/rtf format -->The
following code snippet not works correctly.</span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'> </span></f=
ont></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>>data Obj =
=3D Obj {_id,
p1, p2::Int} deriving (Show, Read)</span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'> </span></f=
ont></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>>showObj :: =
Obj ->
String</span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>>showObj o =
=3D show o</span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'> </span></f=
ont></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>>main =3D do =
print (showObj
(read "Obj {_id=3D1,p1=3D10,p2=3D20}"))</span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>> =
return ()</span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'> </span></f=
ont></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>The reason is =
because I
used the property name with underscore char like =
“_id”.</span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>Looking into =
auto
generated class codes and seeing they show it should encompass =
identifiers with
special characters with parenthesis, so I tried "Obj =
{(_id)=3D1,p1=3D10,p2=3D20}"
as argument of read func. But, the result is same, parse =
error.</span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'> </span></f=
ont></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>Is this problem
by-design or bug? Or Am I missing any point?</span></font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'> </span></f=
ont></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>Thanks,</span></=
font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'>/JongKeun</span>=
</font></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'> </span></f=
ont></p>
<p class=3DMsoNormal><font size=3D2 color=3Dblue face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma;color:blue'> </span></f=
ont></p>
<p class=3DMsoNormal style=3D'margin-left:39.95pt'><font size=3D2 =
face=3DTahoma><span
lang=3DEN-US style=3D'font-size:10.0pt;font-family:Tahoma'>-----Original
Message-----<br>
<b><span style=3D'font-weight:bold'>From:</span></b> Simon Peyton-Jones =
<br>
<b><span style=3D'font-weight:bold'>Sent:</span></b> Friday, February =
07, 2003
5:41 PM<br>
<b><span style=3D'font-weight:bold'>To:</span></b> Jong Keun Na;
haskell-cafe@haskell.org<br>
<b><span style=3D'font-weight:bold'>Subject:</span></b> RE: Auto =
generated
instance codes through 'deriving'</span></font></p>
<p class=3DMsoNormal style=3D'margin-left:39.95pt'><font size=3D3
face=3D"Times New Roman"><span lang=3DEN-US =
style=3D'font-size:12.0pt'> </span></font></p>
<p class=3DMsoNormal style=3D'margin-left:39.95pt'><font size=3D2 =
color=3Dnavy
face=3DArial><span lang=3DEN-GB =
style=3D'font-size:10.0pt;font-family:Arial;
color:navy'>Try -ddump-deriv</span></font></p>
<p class=3DMsoNormal style=3D'margin-left:39.95pt'><font size=3D2 =
color=3Dnavy
face=3DArial><span lang=3DEN-GB =
style=3D'font-size:10.0pt;font-family:Arial;
color:navy'> &=
nbsp;
http://haskell.cs.yale.edu/ghc/docs/latest/html/users_guide/options-debug=
ging.html#DUMPING-OUTPUT</span></font></p>
<p class=3DMsoNormal style=3D'margin-left:39.95pt'><font size=3D2 =
color=3Dnavy
face=3DArial><span lang=3DEN-GB =
style=3D'font-size:10.0pt;font-family:Arial;
color:navy'> </span></font></p>
<p class=3DMsoNormal style=3D'margin-left:39.95pt'><font size=3D2 =
color=3Dnavy
face=3DArial><span lang=3DEN-GB =
style=3D'font-size:10.0pt;font-family:Arial;
color:navy'>Simon</span></font></p>
<p class=3DMsoNormal style=3D'margin-left:39.95pt'><font size=3D2 =
color=3Dnavy
face=3DArial><span lang=3DEN-GB =
style=3D'font-size:10.0pt;font-family:Arial;
color:navy'> </span></font></p>
<div style=3D'border:none;border-left:solid blue 1.5pt;padding:0cm 0cm =
0cm 4.0pt'>
<p class=3DMsoNormal style=3D'margin-left:39.95pt'><font size=3D2 =
face=3DTahoma><span
lang=3DEN-US style=3D'font-size:10.0pt;font-family:Tahoma'>-----Original
Message-----<br>
<b><span style=3D'font-weight:bold'>From:</span></b> Jong Keun Na
[mailto:jongkn@microsoft.com] <br>
<b><span style=3D'font-weight:bold'>Sent:</span></b> 07 February 2003 =
06:15<br>
<b><span style=3D'font-weight:bold'>To:</span></b> =
haskell-cafe@haskell.org<br>
<b><span style=3D'font-weight:bold'>Subject:</span></b> Auto generated =
instance
codes through 'deriving'</span></font></p>
<p class=3DMsoNormal style=3D'margin-left:39.95pt'><font size=3D3
face=3D"Times New Roman"><span lang=3DEN-GB =
style=3D'font-size:12.0pt'> </span></font></p>
<p style=3D'margin-left:39.95pt'><font size=3D2 face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma'>Hello =
folks,</span></font></p>
<p style=3D'margin-left:39.95pt'><font size=3D2 face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma'>Is there any =
method</span></font><span
lang=3DEN-US> </span><font size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:
10.0pt;font-family:Tahoma'>with which I can see</span></font><span =
lang=3DEN-US> </span><font
size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:10.0pt;font-family:Tahoma'>instance’s</span></fo=
nt><span
lang=3DEN-US> </span><font size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:
10.0pt;font-family:Tahoma'>codes</span></font><span lang=3DEN-US> =
</span><font
size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:10.0pt;font-family:Tahoma'>generated
automatically</span></font><span lang=3DEN-US> </span><font size=3D2 =
face=3DTahoma><span
lang=3DEN-US style=3D'font-size:10.0pt;font-family:Tahoma'>by =
using</span></font><span
lang=3DEN-US> </span><font size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:
10.0pt;font-family:Tahoma'>‘<b><span =
style=3D'font-weight:bold'>deriving’</span></b>
keyword in GHC?</span></font></p>
<p style=3D'margin-left:39.95pt'><font size=3D2 face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma'>I’m curious in how =
GHC
generates</span></font><span lang=3DEN-US> </span><font size=3D2 =
face=3DTahoma><span
lang=3DEN-US =
style=3D'font-size:10.0pt;font-family:Tahoma'>‘<b><span
style=3D'font-weight:bold'>Read’</span></b></span></font><span =
lang=3DEN-US> </span><font
size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:10.0pt;font-family:Tahoma'>class’s</span></font>=
<span
lang=3DEN-US> </span><font size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:
10.0pt;font-family:Tahoma'>instance code for</span></font><span =
lang=3DEN-US> </span><font
size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:10.0pt;font-family:Tahoma'>user-defined</span></font><=
span
lang=3DEN-US> </span><font size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:
10.0pt;font-family:Tahoma'>data type.</span></font></p>
<p style=3D'margin-left:39.95pt'><font size=3D2 face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma'>Any</span></font><span =
lang=3DEN-US> </span><font
size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:10.0pt;font-family:Tahoma'>help
will be</span></font><span lang=3DEN-US> </span><font size=3D2 =
face=3DTahoma><span
lang=3DEN-US =
style=3D'font-size:10.0pt;font-family:Tahoma'>great</span></font><span
lang=3DEN-US> </span><font size=3D2 face=3DTahoma><span lang=3DEN-US =
style=3D'font-size:
10.0pt;font-family:Tahoma'>appreciated.</span></font></p>
<p style=3D'margin-left:39.95pt'><font size=3D2 face=3DTahoma><span =
lang=3DEN-US
style=3D'font-size:10.0pt;font-family:Tahoma'>/JongKeun</span></font></p>=
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