Inside the Simulink Library "User Defined Functions" section, there are about 16 different kinds of blocks. I'm guessing you are talking about the MATLAB Function Block kind.
If that guess is correct, this information may help.
MATLAB code inside a MATLAB Function Block or called by that code is handled by MathWorks code generation technologies even for simulation. Those technologies place some restrictions on the use of numerictype and fixdt.
Neither fixdt nor numerictype can be function argument, use dummy var instead
I believe neither numeric type object can be an input or output argument of a MATLAB function being handled by code generation technologies. The technique to pass numeric type information in or out of these functions is to create a dummy constant variable.
dummyVarToHoldDataType = fi( 0, numerictype( 1, 8, 7 ) )
dummyVarToHoldDataType =
0
DataTypeMode: Fixed-point: binary point scaling
Signedness: Signed
WordLength: 8
FractionLength: 7
numerictype OK in body, but not fixdt, until R2024a
Inside the body of the MATLAB function being handled by coder technologies you can create numerictype variables. But again, I believe these can't cross function boundaries, that variable needs to stay inside that function body.
Suppose you passed numeric type information into a function using a dummy variable, you could then extract that information to a numerictype object using this utility.
nt = fixed.extractNumericType(dummyVarToHoldDataType)
nt =
DataTypeMode: Fixed-point: binary point scaling
Signedness: Signed
WordLength: 8
FractionLength: 7
FYI: fixed.extractNumericType can support many other types of inputs.
help fixed.extractNumericType
extractNumericType Extract embedded.numerictype from input.
T = fixed.extractNumericType(X) returns an embedded.numerictype
object that is extracted from numeric value input X, or is
specified by the input argument X.
The following inputs are supported.
Numeric values:
MATLAB's 11 builtin numeric type variables
double, single, logical, int8, ... uint64
Half-precision floating-point (half)
Fixed-point numeric object (fi)
Numeric type specification objects:
embedded.numerictype objects
Simulink.NumericType objects
Data type name strings:
Class name of MATLAB's 11 builtin numeric types
'double', 'single', 'logical', 'int8', ... 'uint64'
Simulink's canonical name of a data type (not aliases)
'bool','sfix16_En3'
Constructor strings that evaluate to a numeric type object:
embedded.numerictype
'numerictype(1,33,55)'
Simulink.NumericType
'fixdt(0,77,22)'
Examples:
% To extract the numeric type from a numeric value:
T = fixed.extractNumericType(pi) % numerictype('double')
T = fixed.extractNumericType(single(pi)) % numerictype('single')
T = fixed.extractNumericType(half(pi)) % numerictype('half')
T = fixed.extractNumericType(int8(0)) % numerictype(1,8,0)
T = fixed.extractNumericType(fi(pi,1,24,12)) % numerictype(1,24,12)
% To extract the numeric type from a numeric type specification object:
T = fixed.extractNumericType(numerictype(1,32,16)) % numerictype(1,32,16)
T = fixed.extractNumericType(fixdt(0,18,0)) % numerictype(0,18,0)
% To extract the numeric type from a data type name string:
T = fixed.extractNumericType('int8') % numerictype(1,8,0)
T = fixed.extractNumericType('sfix16_En3') % numerictype(1,16,3)
% To extract the numeric type from a constructor string:
T = fixed.extractNumericType('numerictype(1,33,55)') % numerictype(1,33,55)
T = fixed.extractNumericType('fixdt(0,77,22)') % numerictype(0,77,22)
See also fi, numerictype, fixdt.
Documentation for fixed.extractNumericType
doc fixed.extractNumericType
In R2023b and earlier, a fixdt object cannot be used inside the body of a function being handled by coder technologies.
Once R2024a ships, that restriction on fixdt will be removed.
