HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 287

The Branch commands, IF <test> THEN <true clause> [ELSE <false clause>] END, CASE <if clauses> …END:

Page 287 highlights

The Branch commands IF THEN [ELSE ] END Note the need for a double = sign when comparing equalities. Any number of statements can be placed in the true and false sections. Enclosing brackets are not required, as they are in some other languages. CASE ...END: This command removes the need for nested IF commands but is only worth it if you have more than two or three nested IFs. Note that colons are not required for the ENDs which terminate the internal IF clauses. IFFERR THEN [ELSE ] END This can be used to error trap programs where there is a possibility of something going wrong which would normally crash the program, such as evaluating a function at a point for which it is undefined. By trapping the suspect code you can supply an alternative which will perform some other action. This will tend to make your programs more user friendly and is a very good idea! 287

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The Branch commands
IF <test> THEN <true clause> [ELSE <false clause>] END
Note the need for a double
=
sign when comparing equalities. Any
number of statements can be placed in the true and false sections.
Enclosing brackets are not required, as they are in some other
languages.
CASE <if clauses> …END:
This command removes the need for nested
IF
commands but is only
worth it if you have more than two or three nested
IF
s. Note that colons
are not required for the
END
s which terminate the internal
IF
clauses.
IFFERR <statements> THEN <statements> [ELSE <statements>] END
This can be used to error trap programs where there is a possibility of
something going wrong which would normally crash the program, such
as evaluating a function at a point for which it is undefined. By trapping
the suspect code you can supply an alternative which will perform some
other action. This will tend to make your programs more user friendly
and is a very good idea!
287