@spec fun(MapSorter.SortSpecs.t()) :: comp_fun()

Generates an Enum.sort/2 compare function from a list of sort specs.

Examples

iex> alias MapSorter.Compare
iex> sort_specs = [:dob, desc: :likes]
iex> fun = Compare.fun(sort_specs)
iex> is_function(fun, 2)
true

# Compare function always true => no reordering...
iex> alias MapSorter.Compare
iex> sort_specs = {:dob, desc: :likes}
iex> fun = Compare.fun(sort_specs)
iex> is_function(fun, 2) and fun.(1, 2) and fun.(:any, 'any')
true

iex> alias MapSorter.Compare
iex> sort_specs = fn -> [:dob, desc: :likes] end
iex> fun = Compare.fun(sort_specs.())
iex> is_function(fun, 2)
true

iex> alias MapSorter.Compare
iex> sort_specs = Tuple.to_list({:dob, {:desc, :likes}})
iex> fun = Compare.fun(sort_specs)
iex> is_function(fun, 2)
true

@spec heredoc(MapSorter.SortSpecs.t()) :: String.t()

Generates a cond/1 expression as a heredoc to become a compare function.

The heredoc may be converted into its quoted form at compile time or else have its contents evaluated at runtime.

This function cannot be named cond as it is among the Kernel.SpecialForms.

Examples

iex> alias MapSorter.Compare
iex> Compare.heredoc([])
"""
& cond do
true -> true or &1 * &2
end
"""

iex> alias MapSorter.Compare
iex> sort_specs = [:name, {:desc, :dob}]
iex> Compare.heredoc(sort_specs)
"""
& cond do
&1[:name] < &2[:name] -> true
&1[:name] > &2[:name] -> false
&1[:dob] > &2[:dob] -> true
&1[:dob] < &2[:dob] -> false
true -> true or &1 * &2
end
"""

iex> alias MapSorter.Compare
iex> sort_specs = [:name, {:desc, {:dob, Date}}]
iex> Compare.heredoc(sort_specs)
"""
& cond do
&1[:name] < &2[:name] -> true
&1[:name] > &2[:name] -> false
&1[:dob] != nil and Date.compare(&1[:dob], &2[:dob]) == :gt -> true
&1[:dob] != nil and Date.compare(&1[:dob], &2[:dob]) == :lt -> false
true -> true or &1 * &2
end
"""

iex> alias MapSorter.Compare
iex> sort_specs = [:name, {:desc, {:account, Path}}]
iex> Compare.heredoc(sort_specs)
"""
& cond do
&1[:name] < &2[:name] -> true
&1[:name] > &2[:name] -> false
&1[{:account, Path}] > &2[{:account, Path}] -> true
&1[{:account, Path}] < &2[{:account, Path}] -> false
true -> true or &1 * &2
end
"""