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Navigation: Language Reference > Statements > If Then Else (expression) |
  
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y = if condition then
expression
else
expression
end;
The if-then-else expression evaluates a condition and makes y equal to the first expression if the condition is true and makes y equal to the second expression if the condition is true. If the condition is true, 20-sim ignores the second expression. If the condition is false, 20-sim ignores the first expression. Because the complete construct forms one expression, only one semicolon is used at the end.
If-then-else expression may be nested. Take care that no semicolons are used, because no matter how large the construct is, it is still one expression!
y = if time > 5 then
-ramp(1) // statement to be assigned to y if condition is true,
else
ramp(1) // statement to be assigned to y if condition is false,
end;
// Nesting:
x = if time < 1 then
1
else
if time < 2 then
2
else
if time == 2 then
1
else
0
end
end
end;
| 1. | The output of the condition must be a boolean. |
| 2. | If needed, always use the equal operator (==) in the condition. |
Note
| 1. | Take care when using event functions in if-then-else expressions. In if-then-else expressions only the equations of the true parts are evaluated, so event functions may not always be triggered! |
| 2. | There is also an if-then-else statement. |
| 3. | Equations within an if statement have to be written in the correct order of execution, i.e. they are not rewritten into a causal form but executed sequentially. |