Computer versions of APL (A
Programming Language) evolved from the algorithmic notation of K. E. Iverson.
APL was implemented as an interactive language by Iverson, Falkof and others at
IBM as APL 360. APL is similar to algebraic notation, but interprets
expressions right to left. APL uses special symbols. The Text
Keyboard used for APL in MYSYS and MYNET. Some comparison of APL with
other traditional computer languages is given in APL is not A Programming
Language. Also in Iverson _ APL + J
Four APL*PLUS interpreters were available for
small computers at UNB. APL/PC, originally for 8088 and
similar machines, APLII with the same features as APL2
by IBM requires a 80386 or higher. APLIII
similar to APLII but for Windows. APL+Windows. These have now been discontinued, but various versions are
available commercially. A number of APL workspaces are included in NUNET. See
the Tools page.
APL uses common algebraic, Greek letters, & other symbols to represent useful
primitive functions and operators..
Consult texts such as 'APL IS EASY', 'APL an
interactive approach' by GILMAN and ROSE, for the basics of APL programming.
See the APL*PLUS documentation for a complete listing of functions, features
and system supplied workspaces.
When not in a defined function (fn) you are in APLie. When 'Enter'
is keyed in APLie the line marked by the cursor on
the computer display is interpreted. This is referred to as Entering. If the
line follows APL syntax rules, it is executed and the result displayed,
otherwise an error message describes why the interpretation failed. APL runs in
a session manager and the default is APLie.
Functions behave like verbs, variables and
constants like nouns, etc. They can be combined as in math. E.g. 3+4 is a
sequence of the constant 3, primitive + and constant 4. Enter 3+4 on one line,
the result 7 will show on the next.
This works with a+b,
where a and b are algebraic variable names. Values
must be assigned to a and b for APL to interpret the a+b expression, otherwise a 'value error' will result. a3 and b4 assigns values. Interpreting a+b
will then produce the same result as 3+4. This is a dyadic or two variable use
of the primitive +. The algebraic y=a+b means the
same as ya+b in APL. Any expression written in
correct APL syntax and where the required information is complete will be
executed when entered. Expressions can be up to 255 characters long. APL does
not have precedence rules like algebra and relies on the right to left sequence
and parentheses for the order of execution.
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End to date: 070828, ams
