Invalid default value for property error in class properties

Greeting

I made a class and run dthe code in .m file

classdef myclass
    properties (Constant)
        a=physconst('LightSpeed');
        b=a/2
    end
end

it occurs error and says

Invalid default value for property 'b' in 'myclass':

Unrecognized function or variable 'a'.

physconst("LightSpeed") is a function in addon which name is 'Phased Array System Toolbox'

and its version is 4.3

a=physconst('LightSpeed')
b=a/2

I put thosdde two lines in command window

and it works fine...

so I have removed constant and tried to initialize them with class constructor

classdef myclass
    properties
        a;
        b;
    end
    methods
        function obj=myclass(obj)
            a=physconst('LightSpeed');
            b=a/2;
        end
    end
end

but the same error occured

I want to initialize my class property value with addon function but it have bring out error

How to deal with this error?

Answer 1

[per isakson]

In the properties block one must refer to a as MyClass.a when Constant.

>> mc = MyClass
mc = 
  MyClass with properties:
    a: 299792458
    b: 149896229
>> which physconst -all
C:\Program Files\MATLAB\R2018b\toolbox\shared\siglib\physconst.m
>> 

where

classdef MyClass
    properties (Constant)
        a = physconst('LightSpeed');
        b = MyClass.a/2;
    end
end

In your second class definition the constructor

function obj=myclass(obj)
    a=physconst('LightSpeed');
    b=a/2;
end

shall be

function obj=myclass()
    obj.a = physconst('LightSpeed');
    obj.b = obj.a /2;
end

[NoYeah]

thank you sir, I love you