(no subject)

Fri, 13 Sep 2002 12:12:02 -0700

This is a multi-part message in MIME format.

------=_NextPart_000_001C_01C25B1E.CB0BCD50
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: 7bit

I'm just learning Haskell with Hugs98. I can't understand why the line
defining "foo" is acceptable while the line defining "bar" (only
difference is the unary minus) generates the error message at the end.
If someone could explain this, or, better yet, tell me how I can figure
this out for myself. Thanks.

data Entry = Ent {date :: String, amount :: Double}
foo = [Ent "baz"  1.0]
bar = [Ent "baz" -1.0]

Type checking......
ERROR "...test.hs":7 - Unresolved top-level overloading
*** Binding             : bar
*** Outstanding context : Fractional (Double -> Entry)

------=_NextPart_000_001C_01C25B1E.CB0BCD50
Content-Type: text/html;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable

<html xmlns:o=3D"urn:schemas-microsoft-com:office:office" =
xmlns:w=3D"urn:schemas-microsoft-com:office:word" =
xmlns=3D"http://www.w3.org/TR/REC-html40">

<head>
<META HTTP-EQUIV=3D"Content-Type" CONTENT=3D"text/html; =
charset=3Dus-ascii">

<meta name=3DProgId content=3DWord.Document>
<meta name=3DGenerator content=3D"Microsoft Word 10">
<meta name=3DOriginator content=3D"Microsoft Word 10">
<link rel=3DFile-List href=3D"cid:filelist.xml@01C25B1E.C48EE200">
<!--[if gte mso 9]><xml>
 <o:OfficeDocumentSettings>
  <o:DoNotRelyOnCSS/>
 </o:OfficeDocumentSettings>
</xml><![endif]--><!--[if gte mso 9]><xml>
 <w:WordDocument>
  <w:GrammarState>Clean</w:GrammarState>
  <w:DocumentKind>DocumentEmail</w:DocumentKind>
  <w:EnvelopeVis/>
  <w:Compatibility>
   <w:BreakWrappedTables/>
   <w:SnapToGridInCell/>
   <w:WrapTextWithPunct/>
   <w:UseAsianBreakRules/>
  </w:Compatibility>
  <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel>
 </w:WordDocument>
</xml><![endif]-->
<style>
<!--
 /* Font Definitions */
 @font-face
	{font-family:CMTT10;
	panose-1:0 0 0 0 0 0 0 0 0 0;
	mso-font-charset:0;
	mso-generic-font-family:auto;
	mso-font-format:other;
	mso-font-pitch:auto;
	mso-font-signature:3 0 0 0 1 0;}
 /* Style Definitions */
 p.MsoNormal, li.MsoNormal, div.MsoNormal
	{mso-style-parent:"";
	margin:0in;
	margin-bottom:.0001pt;
	mso-pagination:widow-orphan;
	font-size:12.0pt;
	font-family:"Times New Roman";
	mso-fareast-font-family:"Times New Roman";}
a:link, span.MsoHyperlink
	{color:blue;
	text-decoration:underline;
	text-underline:single;}
a:visited, span.MsoHyperlinkFollowed
	{color:purple;
	text-decoration:underline;
	text-underline:single;}
span.ital
	{mso-style-name:ital;
	mso-ansi-font-size:11.0pt;
	mso-bidi-font-size:11.0pt;
	font-family:CMTT10;
	mso-ascii-font-family:CMTT10;
	mso-hansi-font-family:CMTT10;
	mso-bidi-font-family:CMTT10;
	font-style:italic;
	mso-bidi-font-style:normal;}
span.EmailStyle18
	{mso-style-type:personal-compose;
	mso-style-noshow:yes;
	mso-ansi-font-size:10.0pt;
	mso-bidi-font-size:10.0pt;
	font-family:Arial;
	mso-ascii-font-family:Arial;
	mso-hansi-font-family:Arial;
	mso-bidi-font-family:Arial;
	color:windowtext;}
span.GramE
	{mso-style-name:"";
	mso-gram-e:yes;}
@page Section1
	{size:8.5in 11.0in;
	margin:1.0in 1.25in 1.0in 1.25in;
	mso-header-margin:.5in;
	mso-footer-margin:.5in;
	mso-paper-source:0;}
div.Section1
	{page:Section1;}
-->
</style>
<!--[if gte mso 10]>
<style>
 /* Style Definitions */=20
 table.MsoNormalTable
	{mso-style-name:"Table Normal";
	mso-tstyle-rowband-size:0;
	mso-tstyle-colband-size:0;
	mso-style-noshow:yes;
	mso-style-parent:"";
	mso-padding-alt:0in 5.4pt 0in 5.4pt;
	mso-para-margin:0in;
	mso-para-margin-bottom:.0001pt;
	mso-pagination:widow-orphan;
	font-size:10.0pt;
	font-family:"Times New Roman";}
</style>
<![endif]-->
</head>

<body lang=3DEN-US link=3Dblue vlink=3Dpurple =
style=3D'tab-interval:.5in'>

<div class=3DSection1>

I&#8217;m just learning Haskell with Hugs98. I =
can&#8217;t
understand why the line defining &#8220;foo&#8221; is acceptable while =
the line
defining &#8220;bar&#8221; (only difference is the unary minus) =
generates the
error message at the end. If someone could explain this, or, better yet, =
tell
me how I can figure this out for myself. =
Thanks.<o:p></o:p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p>&nbsp;</o:p></span></font></p>

<p class=3DMsoNormal><span class=3DGramE><font size=3D2 =
face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>data</span></font></span><fo=
nt
size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;font-family:Arial'> Entry =3D Ent
{date :: String, amount :: Double}<o:p></o:p></span></font></p>

<p class=3DMsoNormal><span class=3DGramE><font size=3D2 =
face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>foo</span></font></span><fon=
t
size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;font-family:Arial'> =3D [Ent
&quot;baz&quot;<span style=3D'mso-spacerun:yes'>&nbsp; =
</span>1.0]<o:p></o:p></span></font></p>

<p class=3DMsoNormal><span class=3DGramE><font size=3D2 =
face=3DArial><span
style=3D'font-size:10.0pt;font-family:Arial'>bar</span></font></span><fon=
t
size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;font-family:Arial'> =3D [Ent
&quot;baz&quot; -1.0]<o:p></o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p>&nbsp;</o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Type checking......<o:p></o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>ERROR &quot;...test.hs&quot;:7 - Unresolved top-level
overloading<o:p></o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>*** Binding<span
style=3D'mso-spacerun:yes'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;
</span>: bar<o:p></o:p></span></font></p>

<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>*** Outstanding <span class=3DGramE>context :</span>
Fractional (Double -&gt; Entry)<o:p></o:p></span></font></p>

</div>

</body>

</html>

------=_NextPart_000_001C_01C25B1E.CB0BCD50--