HP 48G - Page 31

You'll find most of the commonly used postfix pro-
gramming commands collected in groups under the
key. Recall that all postfix commands consume
their arguments before leaving their stack results (if
any). Here is an overview of the various groups, with
some highlights noted (for more details on a com-
mand, see the Command Index on pages 41-77):
The program branching commands (under IEFE)
let you build programs that make execution decisions
“on the fly,” testing values or conditions and directing
program control according to the results of those tests
via constructs such as I[F-THEM-ELSE, START-STEF,
FOR-MEST, OO-UMTIL, WHILE-FEFEHT, and CHSE state-
ments. Notes: Thetestthattriggers abranching deci-
sion may be of any length; the sole issue is whether
its ultimate resultis zero (false) or non-zero (true). For
program repetitions (“loops”), use “TART orF O if you
know the number of repetitions; use [ or WHILE if
you don't.
The testcommands (under [l test the states of
flags or compare values, allowing decisions (such as
program branching—see above) during program ex-
ecution. Notes: The logical tests (HMO, OF, HOF and
MOT) let you form compound tests by combining what
would otherwise be separate tests. Two of the flag
tests (FSTC and FLTC) clear the given flag after test-
ingits status. The two equality tests, == and SAI'E , are
similar except when testing algebraic objects.
The type commands (under [EETI) offer commands
that form various object types from their constituent
parts. Notes: As for the converse, the one necessary
command—an all-purpose object de-constructor (for
most object types)—is [IE.l+. Also, two commands
(TYPE andYT'PE) test the type of a given object (see
also page 1).
The list commands (under ERM) offer two groups
of commands. Those in the first group manipulate
just a single given element in a given list; those in the
other group run procedures on all elements in a given
list. Notes: Various combinations of commands such
as HEAD, TAIL, REVLIST and SORT offer powerful
ways to quickly re-order and present lists (and recall
that you can put almost any type of object into a list).
And DOLIST, DOSUE, STREAM and SER will quickly
send each element in turn through a given process,
with the result(s) appearing in a list, too.
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