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Category：Languages

A hash, by default, converts all keys to strings. This causes issues when your keys are numbers which may be close:

`> my %h; %h{1/3} = 1; %h{0.333333} = 2; dd %h; Hash %h = {"0.333333" => 2} `

This can, of course, be fixed as follows:

`> my %h{Real}; %h{1/3} = 1; %h{0.333333} = 2; dd %h; Hash[Any,Real] %h = (my Any %{Real} = 0.333333 => 2, <1/3> => 1) `

But now I need a hash of hashes of numbers, e.g. `{ 1/3 => { 2/3 => 1, 0.666667 => 2 } }`

.

`> my %h{Real}; %h{1/3}{2/3} = 1; %h{1/3}{0.666667} = 2; dd %h; Hash[Any,Real] %h = (my Any %{Real} = <1/3> => ${"0.666667" => 2}) `

How do I fix that?

Best I can figure out is the following workaround:

`> my %h{Real}; %h{1/3} //= my %{Real}; %h{1/3}{2/3} = 1; %h{1/3}{0.666667} = 2; dd %h; Hash[Any,Real] %h = (my Any %{Real} = <1/3> => $(my Any %{Real} = <2/3> => 1, 0.666667 => 2)) `

but that's just annoying.

The following works:

`my Hash[Real,Real] %h{Real}; %h{1/3} .= new; %h{1/3}{2/3} = 1; `

Which is not great.

The following also works as a work-around.

`my Hash[Real,Real] %h{Real}; %h does role { method AT-KEY (|) is raw { my /result = callsame; result .= new unless defined result; result } } %h{1/3}{2/3} = 1; say %h{1/3}{2/3}; # 1 `

If you have more than one such variable:

`role Auto-Instantiate { method AT-KEY (|) is raw { my /result = callsame; result .= new unless defined result; result } } my Hash[Real,Real] %h{Real} does Auto-Instantiate; `