Paris, 2006-02-24APL and OO Morten Kromberg Technical Director, Dyalog Ltd

Paris, 2006-02-24 APL and OO

APL and OO

Morten KrombergTechnical Director, Dyalog Ltd.


Why OO in APL (MUST we)?• Everyone else is doing it• Microsoft says we MUST• Terrorists will attack my system

unless it is running as ”managed” code


Good Reasons for Wanting OOBecause Object Orientation is

a Valuable Tool of Thought!We will be able to Share Tools

and Components more EasilyIt will help us Manage

Complexity in all Project Phases


Agenda

• Introduce Key OO Concepts• Demonstrate the Benefits• Show that APL can Profit from OO

... without losing it’s Soul


Some History...

Back in the old days, in 1962, A feller named Ken Iverson decided what to do. He gathered all the papers he'd been writing for

a spell And he put them in a little book and called it APL.

(first verse of ”APL Blossom Time”)


0 1 2 3 4 5 6 7 8 9 10 1112 13 1415 16 17 18 19 2021 22 2324 25 26

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3Meanwhile, in Oslo...


In Oslo...

SIMULA represents an effort to [describe complex systems as] discrete-event networks, that is, where the flow may be thought of as being composed of discrete units demanding service at discrete service elements, and entering and leaving the elements at definite moments [sic] of time.

Examples of such systems are ticket counter systems, production lines, production in development programs, neuron systems, and concurrent processing of programs on computers.

Kristen Nygaard, Norwegian Computing Centre, ca. 1962


Sons of Norway...

Arrays: SALES←10 11 12 13 15 (+/SALES)÷⍴SALES

Functions: {(+/⍵)÷⍴⍵} SALES

+/ % # SALES

Objects: q←⎕NEW Queue q.Join ⎕NEW Customer 'Jill' q.Join ⎕NEW Customer 'Jack'

q.Length1

Kenneth E. Iverson1920-2004

Kristen Nygaard1926-2002


Stop Me Any Time!


:Class Queue :Field Public History←⍬ Customers←⍬ ⍝ Private Field ∇ r←Length :Access Public r←1⊃⍴Customers ∇ ∇ Join Customer :Access Public Customers←Customers,⊂Customer,(3⊃⎕AI),1+⍴Customers :If 1=⍴Customers ⋄ Serve&0 ⋄ :EndIf ⍝ Start Server ∇ ∇ Serve dummy;t;elapsed ⍝ Start serving queue in new thread when queue length grows to 1 ⍝ Stop when queue is empty. :Repeat ⎕DL 9+?11 ⍝ Processing takes between 10 and 20 seconds elapsed←(3⊃⎕AI)-1 2⊃Customers ⍝ Total time spent in the queue History,←⊂(elapsed,1⊃Customers)[2 1 4] ⍝ History records: Customer, Total Time, Queue Length Customers←1↓Customers ⍝ The customer has left the building :Until 0=⍴Customers ∇ :EndClass ⍝ Class Queue

Queue Class


:Class Queue :Field Public History←⍬ Customers←⍬ ∇ r←Length :Access Public r←1⊃⍴Customers ∇ ∇ Join Customer :Access Public Customers←Customers, ⊂Customer,(3⊃⎕AI),1+⍴Customers :If 1=⍴Customers ⋄ Serve&0 ⋄ :EndIf ∇ ∇ Serve dummy;t;elapsed ⍝ Start serving queue in new thread when queue length grows to 1 ⍝ Stop when queue is empty. :Repeat ⎕DL 9+?11 ⍝ Processing takes between 10 and 20 seconds elapsed←(3⊃⎕AI)-1 2⊃Customers ⍝ Since customer entered queue History,←⊂(elapsed,1⊃Customers)[2 1 4] ⍝ History records (Cust#, Total Time, Initial Queue Length) Customers←1↓Customers ⍝ Customer has left the building :Until 0=⍴Customers ∇ :EndClass ⍝ Class Queue

Queue Class aQueue←⎕NEW Queue


:Class Customer :Field Public CashRequired←60 ⍝ Amount of Cash Required :Field Public SkillLevel←5 ⍝ Average Skills (1-10) :Field Public Sneaky←0 ⍝ Will try to sneak ∇ make args :Access Public :Implements Constructor (CashRequired SkillLevel Sneaky)←args,(⍴,args)↓CashRequired SkillLevel Sneaky ⎕DF '[Customer wanting ',(⍕CashRequired),']' ⍝ Display Form ∇:EndClass ⍝ Customer

Benefit: Object Orientation+ No Type Declarations= Easy Prototyping:


Information Hiding

Specificationshave changed...

A new kind of queue...

Benefit: ”Information Hiding”= Easy Maintenence


Key OO Concepts

• ”Encapsulation”– Related code and data are together

• ”Information Hiding”– Implementor decides what to make

public– Only public behavior is guaranteed– User can rely on ”upwards

compatibility” of public interface


TimeSeries Class

:Class TimeSeries :Field Public Shared DefaultDegree←3 ⍝ 3rd degree polynomials by default

:Field Public Obs ⍝ Observed values :Field Public Degree ⍝ Degree of polynominals to fit

∇ r←PolyFit x;coeffs :Access Public ⍝ Fit polynomial to observed points to compute values at x coeffs←Obs⌹(⍳⍴Obs)∘.*0,⍳Degree ⍝ Find polynomial coeffs r←coeffs+.×⍉x∘.*0,⍳Degree ⍝ Compute fitted f(x) ∇ ∇ make args :Access Public :Implements Constructor Obs←args Degree←DefaultDegree ⍝ Pick up default from Class ∇ :EndClass ⍝ Class TimeSeries


Inheritance

Benefit: Easy & Safe

Code Sharing


Summary of Key Concepts• Method is the OO name for a function• Field is the OO name for a variable• Properties look like Fields, but are

implemented by Get [and Set] functions

• Constructors initialise instances• Destructors clean up


Public vs. Private

• Private members can only be seen by code which is inside the class

• Public members can be seen from inside and outside


Shared vs. Instance

• Shared members are shared by all instances

• They can be used directly from the class without first creating an instance

• Instance members have different content from one instance to the next

• Compiled languages often use the name Static for Shared


Inheritance

• One class can Extend another• This makes code sharing both

easier and safer


New names⎕

• ⎕NEW creates an instance of a class• ⎕CLASS returns the class of an instance• ⎕INSTANCES returns the list of instances

of a class• ⎕THIS returns a reference to the current

instance• ⎕BASE refers to a name in a base class


When NOT to OO


We Want:

Arrays

Functions

Objects

APL

1 2 3

4 5 6

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3

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3


DotNet

• *IS* Important• C# has been our

Design Guide. • Any v11 class can be

used by .Net languages• Managed Code ”Event

Horizon” ~4/5 years• But we want OO under

Windows 32&64, Unix,Linux, and on Pocket PC


To Do List• Unicode (including APL session)• High Precision Arithmetic (& Complex?)• ”Structs”: Classes with Fixed Structure

:Class Employee:Field Public FirstName←'' :Field Public LastName←'’:Field Public Salary←0

:EndClass

• DotNet ”Managed Code” (”Interop” available since version 10)


For More Information

• See Dyalog APL version 11.• Tutorial ”Introduction to OO for

APLers” will be ”serialised” in Vector

• Watch http://www.vector.org.uk• Subscribe to Vector!• Google...!

http://www.vector.org.uk/

http://www.vector.org.uk/


Thanks to...

John Daintree

Geoff Streeter

John Scholes

Pete

Ken

Kristen

... And many, many more ...


Refactoring SQAPL/APL+LinkPro ∇ Test_Old[1] SQAConnect 'C1' 'MS Access Database'

('DriverOptions' 'DBQ=C:\temp\sqaoo.mdb')[2] SQAPrepare 'C1.S1' 'SELECT * FROM EMPLOYEES WHERE FirstName LIKE :<C10:'[3] SQAExec 'C1.S1' 'D%’[4] SQAFetch 'C1.S1' ('Columnwise' 1)[5] SQAClose 'C1' ∇

∇ Test_New;Connection;Sel[1] Connection←⎕NEW SQA.Connection

('MS Access Database' 'DBQ=C:\temp\sqaoo.mdb')[2] Sel←Connection.Prepare 'SELECT * FROM EMPLOYEES

WHERE FirstName LIKE :<C10:'[3] Sel.Columnwise←1[4] Sel.Execute 'D%‘[5] Sel.Fetch 1 ∇


Refactoring SQASet fns ∇ TestSet_Old;z[1] SQAConnect 'C1' 'MS Access Database’

('DriverOptions' 'DBQ=C:\temp\sqaoo.mdb')[2] z←2⊃SQASetPrepare 'C1.S1' 'SELECT ID,SALARY FROM EMPLOYEES'[3] z[;2]×←1+0.1×z[;2]>1000 ⍝ 10% Salary Increase for the Rich[4] SQASetExec'C1.S1' z[5] SQAClose'C1.S1'[6] SQAClose'C1' ∇

∇ TestSet_New;Connection;Set;z[1] Connection←⎕NEW SQA.Connection

('MS Access Database' 'DBQ=C:\temp\sqaoo.mdb')[2] Set←⎕NEW SQA.Set (Connection 'Select ID,SALARY FROM EMPLOYEES')[3] z←Set.Data ⋄ z[;2]×←1+0.1×z[;2]>1000 ⍝ 10% Salary Increase ...[4] Set.Exec z ∇


∇ r←SetExec ctl;cur;⎕IO;c;d;i;m;n;s;t;rcds;data;table ;types;cols;keys;dk;rd[1] ⍝ Execute changes required to update Data Set[2] ⍝ Return 0 (#updates, #inserts, #deletes)[3][4] ⎕IO←1[5] cur rcds←ctl ⋄ n←0 0 0[6] →((⍴d)<i←(d←1⊃⍙SQASets)⍳⊂cur)⍴e1 ⋄ t←(s←1+i)⊃⍙SQASets[7] table cols types keys data←t[8][9] dk←⊂[2]data[;keys] ⋄ rd←⊂[2]rcds[;keys][10] →(0=n[3]←+/m←~dk∊rd)⍴l1[11] →(0≠1⊃r←SetDelete cur(m⌿data[;keys]))⍴0 [12] m←~m ⋄ data←m⌿data ⋄ dk←m/dk[13][14] l1:→(0=n[2]←+/m←(1⊃⍴data)<d←dk⍳rd)⍴l2[15] →(0≠1⊃r←SetInsert cur(m⌿rcds))⍴0[16] m←~m ⋄ rcds←m⌿rcds ⋄ rd←m/rd[17][18] l2:data←data[dk⍳rd;][19] →(0=n[1]←+/m←~∧/rcds≡¨data)⍴l9[20] →(0≠1⊃r←SetUpdate cur(m⌿rcds))⍴0[21] l9:r←0 n ⋄ →0[22][23] e1:r←90003 'Set does not exist' ⋄ →0 ∇

∇ r←Exec rcds;c;d;i;m;n;s;t;dk;rd;data[1] :Access Public[2] ⍝ Execute changes required to update Data Set[3] ⍝ Return 0 (#updates, #inserts, #deletes)[4][5] n←0 0 0[6] data←DATA[7] dk←⊂[2]data[;Keys] ⋄ rd←⊂[2]rcds[;Keys][8] →(0=n[3]←+/m←~dk∊rd)⍴l1[9] →(0≠1⊃r←Delete(m⌿data[;Keys]))⍴0 ⍝ Delete from set[10] m←~m ⋄ data←m⌿data ⋄ dk←m/dk[11][12] l1:→(0=n[2]←+/m←(1⊃⍴data)<d←dk⍳rd)⍴l2[13] →(0≠1⊃r←Insert(m⌿rcds))⍴0[14] m←~m ⋄ rcds←m⌿rcds ⋄ rd←m/rd[15][16] l2:data←data[dk⍳rd;][17] →(0=n[1]←+/m←~∧/rcds≡¨data)⍴l9[18] →(0≠1⊃r←Update(m⌿rcds))⍴0[19] l9:r←0 n ⋄ →0 ∇


∇ r←SQASetUpdate ctl;cur;⎕IO;c;d;i;j;m;s;t;rcds;data ;table;cols;keys;data;stmt;z[1] ⍝ Update records in a Data Set[2][3] ⎕IO←1[4] cur rcds←ctl[5] →((⍴d)<i←(d←1⊃⍙SQASets)⍳⊂cur)⍴e1 ⋄ t←(s←1+i)⊃⍙SQASets[6] table cols types keys data←t[7][8] j←(⍳⍴cols)~keys[9] →(∨/m←(1⊃⍴data)<d←(↓data[;keys])⍳↓rcds[;keys])⍴e2[10][11] t←cols,¨'=',¨types[12] stmt←5↓⊃,/(⊂' AND '),¨cols[keys],¨'=',¨types[keys][13] stmt←'UPDATE ',table,' SET ',(1↓,⊃,/',',¨t[j])[14] stmt←stmt,' WHERE ',stmt[15][16] r←ExecDirect(c←cur,'Update')stmt(rcds[;j,keys])[17] z←Close c[18] →(0<1⊃r)⍴0[19][20] data[d;]←rcds[21] ((s,5)⊃⍙SQASets)←data[22] r←,0 ⋄ →0[23][24] e1:r←90003 'Set does not exist' ⋄ →0[25] e2:r←90005('Keys not in set: ',,' ',⍕m⌿rcds[;keys]) ∇

∇ r←SQA.Set.Update rcds;d;m;j;t;stmt[1] ⍝ Update records in a Data Set[2][3] j←(⍳⍴Cols)~Keys[4] →(∨/m←(1⊃⍴DATA)<d←(⊂[2]DATA[;Keys])⍳⊂[2]rcds[;Keys])⍴e2[5][6] t←Cols,¨'=',¨Types[7] stmt←5↓⊃,/(⊂' AND '),¨Cols[Keys],¨'=',¨Types[Keys][8] stmt←'UPDATE ',Table,' SET ',(1↓,⊃,/',',¨t[j])[9] stmt←stmt,' WHERE ',stmt[10][11] r←Connection.ExecDirect stmt(rcds[;j,Keys])[12] →(r.State≡'Error')⍴e1[13] DATA[d;]←rcds[14] r←,0 ⋄ →0[15][16] e1:(⍕Connection.GetWarning)⎕SIGNAL 90001[17] e2:('Keys not in set: ',,' ',⍕m⌿rcds[;Keys])⎕SIGNAL ∇

Documents

Paris, 2006-02-24APL and OO Morten Kromberg Technical Director, Dyalog Ltd