Iif

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IIf

Conditional function that returns one of two values.

Syntax

IIf ( condition, expr_if_true, expr_if_false )

Parameters

• condition
• expr_if_true
• condition
• expr_if_false
• condition
• expr_if_true

Description

IIf returns a different numeric or string or UDT value (not a reference) depending of the result of a conditional expression evaluated at run-time.
Its typical use is in the middle of an expression; it avoids splitting it to put a conditional in the middle.

IIf only evaluates the expression that it needs to return. This saves time, and can also be useful to prevent evaluating expressions that might be invalid depending on the condition.

When IIf treats expressions of mixed numeric types (conditional expression evaluated at run-time):

Note: If the condition evaluation can be done at compile time (if the comparison expression is a constant), the usage rules are a bit more flexible and IIf can for example return a reference or even return a function call (but not a sub call).

Return Value

if condition is non-zero, expr_if_true, otherwise expr_if_false

Remarks

Dialect Differences

• Not available in the -lang qb dialect unless referenced with the alias __Iif.

Differences from QB

• New to FreeBASIC

See also

• If...Then

Examples

Dim As Integer a, b, x, y, z

a = (x + y + IIf(b > 0, 4, 7)) \ z

is equivalent to:

Dim As Integer a, b, x, y, z, temp

If b > 0 Then temp = 4 Else temp = 7

a = (x + y + temp) \ z

Dim As Integer I

I = -10

Print I, IIf(I>0, "positive", IIf(I=0, "null", "negative"))

I = 0

Print I, IIf(I>0, "positive", IIf(I=0, "null", "negative"))

I = 10

Print I, IIf(I>0, "positive", IIf(I=0, "null", "negative"))

Sleep

Type UDT1

  Dim As Integer I1

End Type

Type UDT2 Extends UDT1

  Dim As Integer I2

End Type

Dim As UDT1 u1, u10 = (1)

Dim As UDT2 u2, u20 = (2, 3)

u1 = IIf(0, u10, u20)

Print u1.I1

u1 = IIf(1, u10, u20)

Print u1.I1

u2 = IIf(0 , u10, u20)

Print u2.I1; u2.I2

'u2 = Iif(1, u10, u20) ''Invalid assignment/conversion

Sleep

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Category: Miscellaneous Keywords
Kind: keyword

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Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.