Beginners September 2008

beginners@lists.squeakfoundation.org

56 participants
87 discussions

Host OS shell call
by Steve Lloyd 13 Sep '08

13 Sep '08

Is there a Squeak class to allow calling a shell command in the host OS and receiving the result? -- International Baccalaureate Steve Lloyd Research Engineer Publications group Peterson House, Malthouse Avenue, Cardiff Gate, CARDIFF CF23 8GL, United Kingdom Tel: +44 29 2054 7869 Fax: +44 29 2054 7778 Web: http://www.ibo.org

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How to remove System Category
by Rob Rothwell 13 Sep '08

13 Sep '08

Hello, How can I remove a System Category in code? I can't quite figure out the usage of SystemOrganizer>>removeSystemCategory: Thanks, Rob

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Passing multiple parameters.
by Charles Gray 13 Sep '08

13 Sep '08

Is it possible to pass multiple parameters to a method? Suppose I want to have a method that solves for x in the quadratic equation, ax^2 + bx +c =0. We know the equation is ((-b + (b*b -4*a*x) sqrt))/(2*a). I want to pass a, b, and c to a method that might be called quadraticSolution. This is a hypothetical question but its answer will help me with something on which I am working.

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Is Squeak Source now the preferred place to publish code?
by Andy Burnett 12 Sep '08

12 Sep '08

When I was looking for a CSV parser, I checked Squeakmap, thinking it was the central repository. However, I subsequently learnt that Avi Bryant had published a very good parser at Squeak Source. Is that now the vest place to look for new code? Thanks AB

1 0

Testing morphs
by Ian J Cottee 11 Sep '08

11 Sep '08

Hi all I've made some progress with my Connectors development. I can see now how I can find out what arrows are connected to what boxes and where they are going. I think ;). And I have now built some subclasses which extend this behaviour for my own purposes. Of course, to test this I should write some tests to prove it. This poses me with a problem. What I do in my user interface is simple - drag a box out, drag another box out and then drag an arrow and connect it to the two of them. But what is simple to do seems to me to be very hard to test, just from a point of view of knowing what's actually happening when I do such things in the UI. What I think I want is a list of all messages that are being sent when I do those things, then I can capture those messages and build my unit tests around them. How can I do that? Or is there another way of testing such things? I'd hoped to gain some knowledge from the Connectors unit tests but there don't seem to be any :-( ... is this an indication that such things are hard to do ? Many thanks again Ian

1 0

Re: What is the simplest way to create a collection from a text file in CSV format?
by Andy Burnett 10 Sep '08

10 Sep '08

<<I ususally do something like this: (((FileStream readOnlyFileNamed: 'file.csv') contentsOfEntireFile " read and close " findTokens: String crlf) " split into lines " reject: [:e | e isEmpty]) " lose empty lines " collect: [:e | e findTokens: $,] " split into fields " Regards, Zulq.>> Andy Burnett wrote: > I have a small database containing questionnaire responses. The DB can > output the responses (mainly descriptive paragraphs) in CSV format. > Ideally, I would like to read each of the records into a collection of > some kind. I was hoping that there might be a 'fromCSV:' method, but I > haven't found one. One approach I had thought about was to edit the > text so in order to create a series of array definitions, and then paste > that into a workspace. However, that does lack a bit of elegance! So, is > there a neat way of doing this? > > Cheers > AB That's great Zulq, much better than my rather procedural attempts. thanks AB

1 0

Newbie seeks advice for working with connectors
by Ian J Cottee 10 Sep '08

10 Sep '08

Hi all I've spent the last month or so working through the Squeak By Example book and now need to actually try to do something in order to make it all gel in my mind. My current requirement seems quite 'simple' to describe but I am not quite sure where to go from here. For a very simple first step I want to take two text boxes, draw an arrow between them and then, when I switch the box 'on' - box1 will send an item (represented as a simple shape) along the arrow to box2. When it reaches box2, box1 will send the next. As each item reaches box2, box2 will be doing 'something'. This is the first stage of modelling a production system where items are sent from machine to machine down a production line. I've found the Connectors framework which solves the problem of drawing boxes and linking them together. What I can't work out is that if I have a box, how do I know what arrows are connected to it? How do I know if the arrow is pointing out of the box or into the box (so should I be sending down it or receiving through it) and how do I animate that arrow to show an item passing down it? I guess the main question is (first of all) just working out what arrows are joined to a box. Having browsed through the classes NCTextRectangleMorph (my current box class) and NCAAConnectorMorph (my current arrow class) I'm none the wiser. Is there any documentation for programming the Connectors framework? I've googled but turned nothing up so far. Any pointers/advice gratefully received. Ian

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What is the simplest way to create a collection from a text file in CSV format?
by Andy Burnett 10 Sep '08

10 Sep '08

I have a small database containing questionnaire responses. The DB can output the responses (mainly descriptive paragraphs) in CSV format. Ideally, I would like to read each of the records into a collection of some kind. I was hoping that there might be a 'fromCSV:' method, but I haven't found one. One approach I had thought about was to edit the text so in order to create a series of array definitions, and then paste that into a workspace. However, that does lack a bit of elegance! So, is there a neat way of doing this? Cheers AB

2 1

still don't understand how to get rid of obsolete classes and bad references
by Freeman Mayberry 10 Sep '08

10 Sep '08

I have been messing around with the obsolete classes in my image and no matter how many times I Garbage collect , set things to nul, clear command histories and numbers of other things I have tried they don't go away. I have read the cleaning up junk article on the wiki along with others. >From what I understand the classes stick around because something is referencing them. How ever when I find an object that is referencing the obsolete class and set that reference to nul, accept the changes it seems like it just comes back later. Am I supposed to set it to nil from something other than an inspector. Why can't I see the obsolete classes in the system browser. -- Freeman Mayberry

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Binary file I/O performance problems
by David Finlayson 08 Sep '08

08 Sep '08

I've been working on my first Smalltalk program which needs to read and write large c structs from a binary file. I wrote two classes BinaryStreamReader and BinaryStreamWriter that take a stream and can read (or write) all of the integer and floating point types I need (also handles byte-swapping if necessary). I wrote a test program that focuses on just reading a small (for us) 123 Mb data file on disk. The program takes about 166 seconds to run compared to 1.2 seconds for an equivalent C version (140x faster than Squeak version). As an example of the style of code I've written, here is the method that reads an unsigned 32-bit integer: uint32 " returns the next unsigned, 32-bit integer from the binary stream " " see PositionableStream for original implimentation." | n a b c d | isBigEndian ifTrue: [ a := stream next. b := stream next. c := stream next. d := stream next ] ifFalse: [ d := stream next. c := stream next. b := stream next. a := stream next ]. ((((a notNil and: [ b notNil ]) and: [ c notNil ])) and: [ d notNil]) ifTrue: [ n := a. n := (n bitShift: 8) + b. n := (n bitShift: 8) + c. n := (n bitShift: 8) + d ] ifFalse: [ n := nil ]. ^ n There are at 4 calls to stream next for each integer and sure enough, a profile of the code (attached below) shows that most of the time is being lost in the StandardFileStream basicNext and next methods. There must be a better way to do this. Scaled up to operational code, I will need to process about 40 Gb of data per day. My C code currently takes about 16 cpu hours to do this work (including number crunching). In Squeak, just reading the data would take 3 cpu months! Hopefully, someone can help me out here. The working code is available on squeaksource.org if anyone is interested: http://www.squeaksource.com/@CWlm_vX4hAPUzk5w/7SVjQQhp Thanks, David Below is a message tally of my program: - 166088 tallies, 166100 msec. **Tree** 100.0% {166100ms} SEAFileReader>>printAllBlocks 99.9% {165934ms} ProcessedPingBlock>>readFrom: 99.9% {165934ms} XYZAPingData>>readFrom: 99.7% {165602ms} XYZATransducerData>>readFrom: 95.9% {159290ms} XYZAPointData>>readFrom: 46.4% {77070ms} BinaryStreamReader>>double |41.9% {69596ms} BinaryStreamReader>>uint32 | |28.1% {46674ms} StandardFileStream>>next | | |14.1% {23420ms} primitives | | |14.0% {23254ms} StandardFileStream>>basicNext | |9.8% {16278ms} LargePositiveInteger>>+ | | |6.1% {10132ms} LargePositiveInteger(Integer)>>+ | | | |3.1% {5149ms} primitives | | | |3.0% {4983ms} SmallInteger(Number)>>negative | | |3.7% {6146ms} primitives | |4.1% {6810ms} primitives |2.5% {4153ms} Float class(Behavior)>>new: |2.0% {3322ms} primitives 13.9% {23088ms} BinaryStreamReader>>float |10.4% {17274ms} BinaryStreamReader>>uint32 | |7.0% {11627ms} StandardFileStream>>next | | |3.5% {5814ms} primitives | | |3.5% {5814ms} StandardFileStream>>basicNext | |2.4% {3986ms} LargePositiveInteger>>+ |2.2% {3654ms} Float class>>fromIEEE32Bit: 13.7% {22756ms} BinaryStreamReader>>int32 |7.7% {12790ms} BinaryStreamReader>>uint32 | |6.8% {11295ms} StandardFileStream>>next | | 3.5% {5814ms} StandardFileStream>>basicNext | | 3.4% {5647ms} primitives |5.2% {8637ms} SmallInteger>>>= | 4.3% {7142ms} SmallInteger(Magnitude)>>>= | 3.5% {5814ms} SmallInteger>>< | 2.6% {4319ms} SmallInteger(Integer)>>< 10.7% {17773ms} BinaryStreamReader>>uint16 |6.9% {11461ms} StandardFileStream>>next | |3.5% {5814ms} StandardFileStream>>basicNext | |3.3% {5481ms} primitives |3.8% {6312ms} primitives 6.8% {11295ms} BinaryStreamReader>>skip: |5.0% {8305ms} StandardFileStream>>skip: 3.4% {5647ms} BinaryStreamReader>>int8 2.6% {4319ms} BinaryStreamReader>>uint8 **Leaves** 25.4% {42189ms} StandardFileStream>>basicNext 25.2% {41857ms} StandardFileStream>>next 6.0% {9966ms} BinaryStreamReader>>uint32 5.6% {9302ms} SmallInteger(Number)>>negative 4.6% {7641ms} LargePositiveInteger>>+ 3.8% {6312ms} LargePositiveInteger(Integer)>>+ 3.8% {6312ms} BinaryStreamReader>>uint16 3.4% {5647ms} Float class(Behavior)>>new: 2.0% {3322ms} BinaryStreamReader>>double **Memory** old +3,705,004 bytes young -28,800 bytes used +3,676,204 bytes free +362,744 bytes **GCs** full 50 totalling 2,524ms (2.0% uptime), avg 50.0ms incr 19959 totalling 2,794ms (2.0% uptime), avg 0.0ms tenures 6,041 (avg 3 GCs/tenure) root table 0 overflows -- David Finlayson, Ph.D. Operational Geologist U.S. Geological Survey Pacific Science Center 400 Natural Bridges Drive Santa Cruz, CA 95060, USA Tel: 831-427-4757, Fax: 831-427-4748, E-mail: dfinlayson(a)usgs.gov

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Beginners September 2008