Operations for Stateflow Data

Stateflow^® charts in Simulink^® models have an action language property that defines the operations that you can use in state and transition actions. The language properties are:

MATLAB^® as the action language.
C as the action language.

Stateflow charts support standard programming operations like addition, comparison, and assignment. The specific operations available depend on the action language of your chart.

Both action languages support basic arithmetic (+, -, *) and comparison (>, <, ==)
C action language supports additional operations like bitwise operators (&, |)
MATLAB action language uses functions for some operations that C does with operators.

All operations work with Stateflow data types including integers, floating-point numbers, and boolean values. For more information, see Differences Between MATLAB and C as Action Language Syntax.

Arithmetic Operations

Use arithmetic operations to perform calculations with sensor values, control signals, and system parameters.

Operation	Precedence	Description	Example
`^`	0	Power	`voltage_squared = voltage ^ 2`
`*`	1	Multiplication	`power = voltage * current`
`/`	1	Division	`efficiency = output_power / input_power`
`+`	2	Addition	`total_force = applied_force + friction_force`
`-`	2	Subtraction	`error = setpoint - measured_value`

Comparison Operations

Use comparison operations to evaluate conditions and thresholds in control logic.

Operation	Precedence	Description	Example
`>`	4	Greater than	if (temperature > max_temp)
`<`	4	Less than	if (pressure < min_pressure)
`>=`	4	Greater than or equal to	if (speed >= target_speed)
`<=`	4	Less than or equal to	if (voltage <= safety_limit)
`==`	5	Equal to	if (mode == CALIBRATION)
`~=`	5	Not equal to (MATLAB)	if (status ~= READY)
`!=`	5	Not equal to (C)	if (status != READY)

Logical Operations

Use logical operations to combine multiple conditions.

Operation	Precedence	MATLAB Action Language	C Action Language
`&&`	9	Logical AND.	Logical AND.
`\|\|`	10	Logical OR.	Logical OR.
`~a`	5	Logical NOT	Logical NOT
`!a`	5	Not supported	Logical NOT

Assignment Operations

Assign values to variables using the = operator:

sensor_reading = adc_value;
control_output = pid_result;

For charts that use C as the action language, you can use these compound assignment operators.

Operation	Equivalent	Example
a += b	`a = a + b`	`accumulator += sample`
`a -= b`	`a = a - b`	`error -= correction`
`a *= b`	`a = a * b`	`gain *= adjustment`
`a /= b`	`a = a / b`	`average /= sample_count`

Increment and Decrement

In charts that use C as the action language, you can use ++ or –- to increment or decrement your data values. For example:

counter++; // Equivalent to counter = counter + 1
sample_index--; // Equivalent to sample_index = sample_index - 1

Type Conversion Operations

You can use MATLAB Type functions in any Stateflow chart.

pressure_int = int16(pressure_reading);
voltage_single = single(voltage_measurement);

Using the cast function is different depending on your action language.

In charts that use MATLAB as the action language, use:

result = cast(sensor_value, "int32");
scaled_value = cast(raw_data, "like", reference_signal);

In charts that use C as the action language, use:

result = cast(sensor_value, int32);
scaled_value = cast(raw_data, type(reference_signal));

Type Cast Operations

To convert a value of one type to another type, use type cast operations. You can cast data to an explicit type or to the type of another variable.

Cast to Explicit Data Type

To cast a numeric expression to an explicit data type, use one of these type conversion functions: double, single, int8, int16, int32, int64, uint8, uint16, uint32, uint64, and boolean. For example, this statement casts the expression x+3 to a 16-bit unsigned integer and assigns the value to the data y:

y = uint16(x+3);

Alternatively, in charts that use MATLAB as the action language, you can use the cast function and specify "double", "single", "int8", "int16", "int32", "int64", "uint8", "uint16", "uint32", "uint64", or "logical" as an input argument. For example, this statement casts the expression x+3 to a 16-bit unsigned integer and assigns the value to y:

y = cast(x+3,"uint16");

To cast an expression to a fixed-point type, charts that use MATLAB as the action language support calling the fi (Fixed-Point Designer) function. For example, this statement casts the expression x+3 as a signed fixed-point value with a word length of eight bits and a fraction length of three bits:

y = fi(x+3,1,8,3);

In charts that use C as the action language, call the cast function using a fixdt (Simulink) expression as an argument. For example, this statement casts the expression x+3 as a signed fixed-point value with a word length of eight bits and a fraction length of three bits:

y = cast(x+3,fixdt(1,8,3));

Cast Type Based on Other Data

To make type casting easier, you can convert the type of a numeric expression to the same type as another Stateflow data.

In charts that use MATLAB as the action language, call the cast function with the keyword "like". For example, this statement converts the value of x+3 to the same type as that of data z and assigns the value to y:

y = cast(x+3,"like",z);

In charts that use C as the action language, the type operator returns the type of an existing Stateflow data. Use this return value in place of an explicit type in a cast operation. For example, this statement converts the value of x+3 to the same type as that of data z and assigns the value to y:

y = cast(x+3,type(z));

Binary Operations

This table summarizes the interpretation of all binary operations in Stateflow charts according to their order of precedence (0 = highest, 10 = lowest). Binary operations are left associative so that, in any expression, operators with the same precedence are evaluated from left to right. The order of evaluation for other operations is unspecified. For example, in this assignment

A = f() > g();

the order of evaluation of f() and g() is unspecified. For more predictable results, it is good coding practice to split expressions that depend on the order of evaluation into multiple statements.

Operation	Precedence	MATLAB as the Action Language	C as the Action Language
`a & b`	6	Logical AND. For bitwise AND, use the `bitand` function.	Bitwise AND (default). Enable this operation by selecting the Enable C-bit operations chart property. Logical AND. Enable this operation by clearing the Enable C-bit operations chart property. For more information, see Bitwise Operations and Enable C-bit operations.
`a ^ b`	7	Not supported. For bitwise XOR, use the `bitxor` function.	Bitwise XOR (default). Enable this operation by selecting the Enable C-bit operations chart property. For more information, see Bitwise Operations and Enable C-bit operations.
`a \| b`	8	Logical OR. For bitwise OR, use the `bitor` function.	Bitwise OR (default). Enable this operation by selecting the Enable C-bit operations chart property. Logical OR. Enable this operation by clearing the Enable C-bit operations chart property. For more information, see Bitwise Operations and Enable C-bit operations.

Operation

Precedence

MATLAB as the Action Language

C as the Action Language

a & b

Logical AND. For bitwise AND, use the bitand function.

Bitwise AND (default). Enable this operation by selecting the Enable C-bit operations chart property.
Logical AND. Enable this operation by clearing the Enable C-bit operations chart property.

For more information, see Bitwise Operations and Enable C-bit operations.

a ^ b

Not supported. For bitwise XOR, use the bitxor function.

Bitwise XOR (default). Enable this operation by selecting the Enable C-bit operations chart property. For more information, see Bitwise Operations and Enable C-bit operations.

a | b

Logical OR. For bitwise OR, use the bitor function.

Bitwise OR (default). Enable this operation by selecting the Enable C-bit operations chart property.
Logical OR. Enable this operation by clearing the Enable C-bit operations chart property.

For more information, see Bitwise Operations and Enable C-bit operations.

Bitwise Operations

This table summarizes the interpretation of all bitwise operations in Stateflow charts that use C as the action language.

Operation	Description
`a & b`	Bitwise AND.
`a \| b`	Bitwise OR.
`a ^ b`	Bitwise XOR.
`~a`	Bitwise NOT.
`a >> b`	Shift `a` to the right by `b` bits.
`a << b`	Shift `a` to the left by `b` bits.

Except for the bit shift operations a >> b and a << b, you must enable all bitwise operations by selecting the Enable C-bit operations chart property. For more information, see Enable C-bit operations.

Bitwise operations work on integers at the binary level. Noninteger operands are first cast to integers. Integer operands follow C promotion rules to determine the intermediate value of the result. This intermediate value is then cast to the type that you specify for the result of the operation.

Note

Bitwise operations are not supported in charts that use MATLAB as the action language. Instead, use the functions bitand, bitor, bitxor, bitnot, or bitshift.

Bitwise Operations and Integer Overflows

This example uses:

Open Model

The implicit cast used to assign the intermediate value of a bitwise operation can result in an overflow. To preserve the rightmost bits of the result and avoid unexpected behavior, disable the chart property Saturate on Integer Overflows.

For example, both charts in this model compute the bitwise operation y = ~u. The charts compute the intermediate value for this operation by using the target integer size of 32 bits, so the 24 leftmost bits in this value are all ones. When the charts assign the intermediate value to y, the cast to uint8 causes an integer overflow. The output from each chart depends on how the chart handles integer overflows.

If Saturate on Integer Overflow is enabled, the chart saturates the result of the bitwise operation and outputs a value of zero.
If Saturate on Integer Overflow is disabled, the chart wraps the result of the bitwise operation and outputs its eight rightmost bits.

Pointer and Address Operations

This table summarizes the interpretation of pointer and address operations in Stateflow charts that use C as the action language.

Operation	Description
`&a`	Address operation. Use with custom code and Stateflow variables.
`*a`	Pointer operation. Use only with custom code variables.

For example, the model sf_bus_demo contains a custom C function that takes pointers as arguments. When the chart calls the custom code function, it uses the & operation to pass the Stateflow data by address. For more information, see Integrate Custom Structures in Stateflow Charts.

Pointer and address operations are not supported in charts that use MATLAB as the action language. Pointers to structures should only be used in read-only mode and are only valid during the call in which they are passed.