The third (as far as I can tell) totally undocumented input argument provides a default value if a specific variable is not found. For example:
function foo()
disp(evalin('base','x','23'))
end
and then
>> clear()
>> foo()
23
>> x = 5;
>> foo()
5
Of course in actual code, it is much better to use efficient methods of passing data between workspaces, rather than slow and obfuscated evalin, in particular passing input/output arguments or using nested functions:
