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Navigation: Language Reference > Statements > If Then Else |
  
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if condition then
equation;
...
else
equation;
...
end;
The if-then-else statement evaluates a condition and performs the first set of equation(s) if the condition is true and the second set of equation(s) if the condition is false. If the condition is true, 20-sim ignores the second set of equation(s). If the condition is false, 20-sim ignores the first set of equation(s).
If-then-else statements may be nested as many times as desired. Do not forget to included the word "end;" to finish every nested statement!
y = step(1);
u = -step(1);
if time > 5 then
y = -ramp(1); // equations to be executed if condition is true,
u = ramp(1); // these are not executed if condition is false
else
y = ramp(1); // equations to be executed if condition is false,
u = -ramp(1); // these are not executed if condition is true
end;
//Nesting
if time < 5 then
a = 1;
b = sin(time*1);
else
if time == 5 then
a = 2;
b = sin(time*2);
else
a = 3
b=sin(time*3);
end;
end;
| 1. | The output of the condition must be a boolean. |
Note
| 1. | Take care when using an event functions in if-then-else statements. In if-then-else statements 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 expression. |
| 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. |