Page 21-50
While this simple construct works fine when your function has only two
branches, you may need to nest IF…THEN…ELSE…END constructs to deal
with function with three or more branches. For example, consider the
function
−
<
≤
<
≤
<
≤
−
<
=
elsewhere
x
if
x
x
if
x
x
if
x
x
if
x
x
f
,
2
15
3
),
exp(
3
5
),
sin(
5
3
,
1
3
,
)
(
2
3
π
π
Here is a possible way to evaluate this function using IF… THEN … ELSE …
END constructs:
IF x<3 THEN
x
2
ELSE
IF x<5 THEN
1-x
ELSE
IF
x<3
π
THEN
sin(x)
ELSE
IF
x<15
THEN
exp(x)
ELSE
-2
END
END
END
END
A complex IF construct like this is called a set of
nested
IF … THEN … ELSE …
END constructs.
A possible way to evaluate f3(x), based on the nested IF construct shown
above, is to write the program: