I am preparing to teach a course this fall from Paul Hudak's _The Haskell School of Expression_. In running Picture.lhs, one of the example programs form the book, I am getting strange graphics behavior. I load the program using ghci and type "main". The graphics window appears, but only one or two of the four shapes is drawn. But if I resize the window (or let the screen or computer sleep and awaken, or cover the window and then uncover it), all four shapes appear. When clicking on a shape to bring it to the front, only the last drawn shape appears on the screen. Again, resizing the window reveals all four shapes drawn correctly.

The fours files needed to produce this behavior are enclosed, and a full session (using the -v flag on ghci) is shown below. I modified the files to use the library Graphics.SOE instead of SOEGraphics, which was needed to run under ghc (as opposed to HUGS).

I am running ghci, version 6.6.1, on an Apple MacBook Pro (2.16 GHz Intel Core Duo, 1 GB 666 MHz Ram) running OS X version 10.4.10. I get similar behavior on an Apple iMac (1.6 GHz PowerPC G5) running 10.4.10.

Scot Drysdale
Professor of Computer Science, Dartmouth College

----------------
scot-macbookpro:~/Documents/Courses/CS 8/SOE/bugtest scot$ ghci -v Picture.lhs
   ___         ___ _
  / _ \ /\  /\/ __(_)
/ /_\// /_/ / / | | GHC Interactive, version 6.6.1, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Using package config file: /opt/local/lib/ghc-6.6.1/package.conf
wired-in package base mapped to base-2.1.1
wired-in package rts mapped to rts-1.0
wired-in package haskell98 mapped to haskell98-1.0
wired-in package template-haskell mapped to template-haskell-2.1
Hsc static flags: -static
Loading package base ... linking ... done.
wired-in package base mapped to base-2.1.1
wired-in package rts mapped to rts-1.0
wired-in package haskell98 mapped to haskell98-1.0
wired-in package template-haskell mapped to template-haskell-2.1
*** Parser:
*** Desugar:
*** Simplify:
*** CorePrep:
*** ByteCodeGen:
*** Parser:
*** Desugar:
*** Simplify:
*** CorePrep:
*** ByteCodeGen:
wired-in package base mapped to base-2.1.1
wired-in package rts mapped to rts-1.0
wired-in package haskell98 mapped to haskell98-1.0
wired-in package template-haskell mapped to template-haskell-2.1
*** Chasing dependencies:
Stable obj: []
Stable BCO: []
unload: retaining objs []
unload: retaining bcos []
Upsweep completely successful.
*** Deleting temp files:
Deleting:
*** Chasing dependencies:
Created temporary directory: /tmp/ghc4524_0
*** Literate pre-processor:
/opt/local/lib/ghc-6.6.1/unlit -h Picture.lhs Picture.lhs /tmp/ ghc4524_0/ghc4524_0.lpp
*** Literate pre-processor:
/opt/local/lib/ghc-6.6.1/unlit -h Region.lhs Region.lhs /tmp/ ghc4524_0/ghc4524_1.lpp
*** Literate pre-processor:
/opt/local/lib/ghc-6.6.1/unlit -h Shape.lhs Shape.lhs /tmp/ghc4524_0/ ghc4524_2.lpp
*** Literate pre-processor:
/opt/local/lib/ghc-6.6.1/unlit -h Draw.lhs Draw.lhs /tmp/ghc4524_0/ ghc4524_3.lpp
Stable obj: []
Stable BCO: []
unload: retaining objs []
unload: retaining bcos []
compile: input file /tmp/ghc4524_0/ghc4524_2.lpp
*** Checking old interface for main:Shape:
[1 of 4] Compiling Shape            ( Shape.lhs, interpreted )
*** Parser:
*** Renamer/typechecker:
*** Desugar:
    Result size = 501
*** Simplify:
    Result size = 910
    Result size = 681
    Result size = 681
*** Tidy Core:
    Result size = 681
*** CorePrep:
    Result size = 831
*** ByteCodeGen:
*** Deleting temp files:
Deleting:
compile: input file /tmp/ghc4524_0/ghc4524_3.lpp
*** Checking old interface for main:Draw:
[2 of 4] Compiling Draw             ( Draw.lhs, interpreted )
*** Parser:
*** Renamer/typechecker:
*** Desugar:
    Result size = 827
*** Simplify:
    Result size = 1173
    Result size = 1093
    Result size = 1093
*** Tidy Core:
    Result size = 1093
*** CorePrep:
    Result size = 1351
*** ByteCodeGen:
*** Deleting temp files:
Deleting:
compile: input file /tmp/ghc4524_0/ghc4524_1.lpp
*** Checking old interface for main:Region:
[3 of 4] Compiling Region           ( Region.lhs, interpreted )
*** Parser:
*** Renamer/typechecker:
*** Desugar:
    Result size = 827
*** Simplify:
    Result size = 1134
    Result size = 945
    Result size = 945
*** Tidy Core:
    Result size = 945
*** CorePrep:
    Result size = 1215
*** ByteCodeGen:
*** Deleting temp files:
Deleting:
compile: input file /tmp/ghc4524_0/ghc4524_0.lpp
*** Checking old interface for main:Picture:
[4 of 4] Compiling Picture          ( Picture.lhs, interpreted )
*** Parser:
*** Renamer/typechecker:
*** Desugar:
    Result size = 1624
*** Simplify:
    Result size = 2423
    Result size = 2083
    Result size = 2083
*** Tidy Core:
    Result size = 2083
*** CorePrep:
    Result size = 2443
*** ByteCodeGen:
*** Deleting temp files:
Deleting:
Upsweep completely successful.
*** Deleting temp files:
Deleting:
Ok, modules loaded: Picture, Region, Shape, Draw.
*Picture> main
*** Parser:
*** Desugar:
*** Simplify:
*** CorePrep:
*** ByteCodeGen:
Loading package X11-1.2.1 ... linking ... done.
Loading package HGL-3.1.1 ... linking ... done.


Attachment: Draw.lhs
Description: Binary data

Attachment: Picture.lhs
Description: Binary data

Attachment: Region.lhs
Description: Binary data

Attachment: Shape.lhs
Description: Binary data

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