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Multiple numerics as one map key / Merge Objects based on parameters

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I want to use two numerics as a single key for a map to merge similar objects of a class. How can I do that?
My class looks like this:
classdef Foo
properties
a double
b double
val double
end
methods
function obj = Foo(a,b,val)
obj.a = a;
obj.b = b;
obj.val = val;
end
function o = plus(l,r)
o = Foo(l.a,l.b,l.val+r.val);
end
function k = getKey(obj)
<...>
end
end
end
The code should do the following:
fooCell = {Foo(3,4,100) Foo(3,4,20) Foo(2,5,20)};
fooMap = containers.Map('KeyType', <...> ,'ValueType','any');
for i=1:length(fooCell)
k = fooCell{i}.getKey;
if fooMap.isKey(k)
fooMap(k) = fooMap(k)+fooCell{i};
else
fooMap(k) = fooCell{i};
end
end
fooMap.values %Should contain 2 objects: Foo(3,4,120) & Foo(2,5,20)
How should the getKey method look like?

Accepted Answer

Jan Siegmund
Jan Siegmund on 3 Jul 2020
The only keytype which can hold two doubles is the character key type. So one may use char as key type and then simply
function k = getKey(obj)
k = num2str([obj.a obj.b],'%d');
end
An even faster approach could be
function k = getKey(obj)
k = char(typecast([obj.a obj.b],'uint16'));
end
As every char in MATLAB is 16bit. This may produce non-printable keys though.

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