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« → x « IF ‘x<3’ THEN ‘x^2‘ ELSE ‘1-x’ END EVAL ”Done” MSGBOX
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and save it under the name ‘f2’. Press
J and verify that variable @@@f2@@@ is
indeed available in your variable menu. Verify the following results:
0 @@@f2@@@ Result: 0 1.2 @@@f2@@@ Result: 1.44
3.5 @@@f2@@@ Result: -2.5 10 @@@f2@@@ Result: -9
These results confirm the correct operation of the IF…THEN…ELSE…END
construct. The program, as written, calculates the function
−
<
=
otherwisex
xifx
xf
,1
3,
)(
2
2
Note: For this particular case, a valid alternative would have been to use an
IFTE function of the form: ‘f2(x) = IFTE(x<3,x^2,1-x)’
Nested IF…THEN…ELSE…END constructs
In most computer programming languages where the IF…THEN…ELSE…END
construct is available, the general format used for program presentation is the
following:
IF logical_statement THEN
program_statements_if_true
ELSE
program_statements_if_false
END
In designing a calculator program that includes IF constructs, you could start
by writing by hand the pseudo-code for the IF constructs as shown above.
For example, for program @@@f2@@@, you could write
IF x<3 THEN
x
2
ELSE
1-x
END
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