If-Else

This example shows how to implement an if-else construct by using Simulink® blocks, Stateflow® Charts, and MATLAB® Function block.

C Construct

if (u1 > u2)
{
  y1 = u1;
}
else
{
  y1 = u2;
}

Modeling Pattern for If-Else: Switch block

One method to create an if-else statement is to use a Switch block from the Simulink > Signal Routing library.

1. Open example model ex_if_else_SL.

The model contains the Switch block with the block parameter Criteria for passing first input of u2~=0. The software selects u1 if u2 is TRUE, otherwise u2 passes.

2. To build the model and generate code, press Ctrl+B.

The code implementing the if-else construct is in the ex_if_else_SL_step function in ex_if_else_SL.c:

/* External inputs (root inport signals with default storage) */
ExternalInputs U;

/* External outputs (root outports fed by signals with default storage) */
ExternalOutputs Y;

/* Model step function */
void ex_if_else_SL_step(void)
{
  /* Switch: '<Root>/Switch' incorporates:
   *  Inport: '<Root>/u1'
   *  Inport: '<Root>/u2'
   *  RelationalOperator: '<Root>/Relational Operator'
   */
  if (U.u1 > U.u2) {
    /* Outport: '<Root>/y1' */
    Y.y1 = U.u1;
  } else {
    /* Outport: '<Root>/y1' */
    Y.y1 = U.u2;
  }

  /* End of Switch: '<Root>/Switch' */
}

Modeling Pattern for If-Else: Stateflow Chart

1. Open example model ex_if_else_SF.

The model contains an If-Else decision pattern that you add by right clicking inside the chart > Add Pattern in Chart > Decision > If-Else.

2. To build the model and generate code, press Ctrl+B.

The code implementing the if-else construct is in the ex_if_else_SF_step function in ex_if_else_SF.c:

/* External inputs (root inport signals with default storage) */
ExternalInputs U;

/* External outputs (root outports fed by signals with default storage) */
ExternalOutputs Y;

/* Model step function */
void ex_if_else_SF_step(void)
{
  /* Chart: '<Root>/Chart' incorporates:
   *  Inport: '<Root>/u1'
   *  Inport: '<Root>/u2'
   */
  /*  If-Else  */
  if (U.u1 >= U.u2) {
    /* Outport: '<Root>/y1' */
    Y.y1 = U.u1;
  } else {
    /* Outport: '<Root>/y1' */
    Y.y1 = U.u2;
  }

  /* End of Chart: '<Root>/Chart' */
}

Modeling Pattern for If-Else: MATLAB Function Block

1. Open example model ex_if_else_ML.

2. The MATLAB Function Block contains this function:

function y1 = fcn(u1, u2)
if u1 > u2;
    y1 = u1;
else y1 = u2;
end

2. To build the model and generate code, press Ctrl+B.

The code implementing the if-else construct is in the ex_if_else_ML_step function in ex_if_else_ML.c:

/* External inputs (root inport signals with default storage) */
ExternalInputs U;

/* External outputs (root outports fed by signals with default storage) */
ExternalOutputs Y;

/* Model step function */
void ex_if_else_ML_step(void)
{
  /* MATLAB Function: '<Root>/MATLAB Function' incorporates:
   *  Inport: '<Root>/u1'
   *  Inport: '<Root>/u2'
   */
  if (U.u1 >= U.u2) {
    /* Outport: '<Root>/y1' */
    Y.y1 = U.u1;
  } else {
    /* Outport: '<Root>/y1' */
    Y.y1 = U.u2;
  }

  /* End of MATLAB Function: '<Root>/MATLAB Function' */
}