Notations (Using Stateflow)

Using Stateflow

ml() Functions

You can specify calls to MATLAB functions that return scalars (of type double) in the action language.

ml() Function Format

The format of the ml() function is

ml(evalString, arg1, arg2, arg3,...);

where the return value is scalar (of type double).

If the result returned is:

A vector, then the first element is returned.
A void, then an appropriate format must be used (an assignment statement cannot be used).
A string, a structure, or a cell array, then the behavior is undefined.

evalString is a string that is evaluated in the MATLAB workspace with formatted substitutions of arg1, arg2, arg3, etc.

Example One: ml() Function Call

This is an example of an ml() function call as part of a condition action.

If S1 is active, an event occurs, and if [c_one] is true, the expression sin(x) is evaluated in the MATLAB workspace and the return value assigned to a. (x must be a variable in the MATLAB workspace and a is a data object in the Stateflow diagram). The result of the evaluation must be a scalar. If x is not defined in the MATLAB workspace, a runtime error is generated.

Example Two: ml() Function Call

This is an example of a ml() function call that passes Stateflow data as arguments. Notice the use of format specifiers %g and %d as are used in the C language function printf.

These data objects are defined:

d1 and a are Local data objects of type double in the Stateflow diagram
d2 is an Output to Simulink data object of type integer in the Stateflow diagram
x must be defined in the MATLAB workspace prior to the execution of the condition action where it is used; if it is not defined, a runtime error is generated.

These three values are passed as arguments to a user-written function. The %g and %d characters are format specifiers that print the current values of d1 and d2 into evalString at appropriate locations.

For example if d1 equals 3.4 and d2 equals 5, using the format specifiers these are mapped into my_func(3.4,x,5). This string is then sent to MATLAB and is executed in the MATLAB workspace.

Example Three: ml() Function Call

This is an example of a ml() function call with string arguments.

These data objects are defined in the Stateflow diagram:

d1 is a Local data object of type double
d2 is an Output to Simulink data object of type integer

The user-written function my_string_func expects four arguments, where the second argument is a string. The %g and %d characters are format specifiers that print the current values of d1 and d2 into evalString at appropriate locations. Notice that the string is enclosed in two single quotes.

Use Guidelines

These guidelines apply to ml() functions:

The first argument must be a string.
If there are multiple arguments, ensure that the number and types of format specifiers (%g, %d, etc.) match the actual number and types of the arguments. These format specifiers are the same as those used in the C function printf.
A scalar (of type double) is returned.
ml() function calls can be nested.
Calls to ml() functions should be avoided if you plan to build an RTW target that includes code from Stateflow Coder.

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