APL in Second Gear. Does APL have a future? What’s the point of APL?

APL in Second Gear

Does APL have a future?

What’s the point of APL?

Did Ken Iverson invent APL?

Did Ken Iverson discover APL?

APL Exists in the Mind of the Beholder

APL is a Tool of Thought

But of whose thoughts?

APL Big Bang Theory

What’s the point of APL?

A notation of direct abstraction is possible

Skip the fluff

Trim the fat

Keep it simple Cut the crap

1-to-1 (notion to notation)

Don’t waste my time

The APL Food Chain

The Consumer

The Business

The Industry Software Expert

The APLer

The Utility Wizard

The APL Interpreter Developer

The Operating System Developer

The Consumer

The Business

The Industry Software Expert

The APLer

The Utility Wizard

The APL Interpreter Developer

The Operating System Developer

The Invisible Utility Wizard

I don’t buy it.We don’t have a Utility Wizard and we don’t

needone. We do just fine.

We already know how to compute an average. We

don’t need another method.

Our method works just fine.

(Prepare to fall in love again.)

A notation of direct abstraction is possible

or

Trim the fat

First gear: Primitives

And so on.

Second gear: Utilities built on primitives

Third gear: Utilities built on utilities

Given today’s date TODAY (yyyymmdd)

and a birthdate DOB (yyyymmdd), what

is the age of the policyholder?

„„

„

Given today’s date TODAY (yyyymmdd)

and the contract date POLDAT (yyyymmdd), how many days has

the policy been in effect?

„

Given today’s date TODAY (yyyymmdd), what will be the date (yyyymmdd) in 90 days,

180 days, 360 days?

„

Format these dates as a 10-column matrix in

mm/dd/yyyy notation.

„

Compute the average ofa set of numbers V.

„

‘‘

1.  Communications2.  User Input3.  Calculations4.  File Handling5.  Reports/output6.  Miscellaneous

File Handling: Given a comma-delimited file that looks like the following, read its fields (except SS No.) into a set of APL variables:

Policy No.,Date of Birth,Sex,SSNo,LastName,Premiums

12614,03/15/1940,M,022-14-1567,Smith,103500

12983,05/30/1937,F,038-15-1129,Jones,58200

„„„„„„„„…„„†

File Handling: Given a fixed-format file with the following layout, read its fields

(except SS No.) into a set of APL variables:

Bytes Length Description

----- ------ -------------

1-8 8 Policy number

9-18 10 Date of birth

19 1 Sex (M or F)

20-30 11 Social Security No.

31-50 20 Last name

51-65 15 Premiums ($)

„„„„„„„„…„„†

File Handling: Save theseAPL variables in an APL file.

…

Calculations: Sum premiums and the

number of policies by year of birth.

„„„›

Reports/output: Generate thisreport, and display it on the screen:

Policy Summary Report

As of 09/22/2009

Number Total

Year of Policies Premium $

---- ----------- ---------

1940 17 12,345

1945 302 3,125,889

1946 45 55,013

„ƒ†Œ„„„„„Œ„„

Reports/output: build thereport as a Word file.

„…„œ„„

Reports/output: build thereport as an .xls file.

…„ƒ†Œ„„„„„„„œ„„„

Communications: Given two .xls filescreated by other functions, send

themas attachments to Fred in

Accounting.

„›œ„œ„œ„œ„œ„œ„„

User Input: Present a menuof choices, from which the

user is to pick one.

„

User Input: Present a menu ofchoices, from which the user

may pick any number of them.

„

User Input: Present a menu of choices, from which the user may pick any number of them. Selected choices are in a list on

the right; remaining choices are in a list on the left; Add/Remove buttons are located in

between.

„

User Input: Present a menu of choices,and allow the user to alter their order by highlighting choices and clicking

the Up or Down buttons.

„

User Input: Present the following input form:

„„„„„„„„„„›„›„›„›„„›„›„›„…„„„

Where have we gone wrong?What’s holding us back?

The ConsumerThe Business

The Industry Software Expert 

The APLerThe Utility Wizard

The APL Interpreter Developer 

The Operating System Developer

The solution: a different(gear-two) mindset.

The APL Interpreter Developer

- Coordinates Wizard communication- Plays “librarian,” not “author”- Documents/distributes both gears

The Utility Wizard

-Works with APLer- Communicates with other Wizards- Develops utilities

The APLer

- Provides feedback to Wizard- Writes APL

APL in Second Gear,The Future of APL