49 lines
2.7 KiB
Markdown
49 lines
2.7 KiB
Markdown
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# Hints
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## General
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- Use `?` to work with the character [code points][codepoint].
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- `\s` can be used to represent a space.
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- Use [integer binary notation][integer-literal] for working with the codes.
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- Try to use the tail call recursion strategy.
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## 1. Encode nucleic acid to binary value
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- This function needs to map one integer to another.
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- This function doesn't need recursion.
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- Making use of multiple clause functions may make this easier by breaking it down.
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## 2. Decode the binary value to the nucleic acid
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- This function is the opposite of part 1's function.
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- This function doesn't need recursion.
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- Making use of multiple clause functions may make this easier by breaking it down.
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## 3. Encode a DNA charlist
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- Create a tail-recursive function which takes a code point from the charlist and recursively builds the bitstring result.
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- Tail-recursive functions need an accumulator.
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- Remember, a [charlist][charlist] is a list of [integer code points][codepoint].
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- You can get the first and remaining items from a list using a built-in [`Kernel` module][kernel] function.
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- You can also pattern match on a list using the [`[head | tail]`][list] notation.
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- Use multiple clause functions to separate the base case from the recursive cases.
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- Do not forget to specify the types of bitstring segments using the `::` operator.
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## 4. Decode a DNA bitstring
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- Create a tail-recursive function which [matches the first 4 bits][bitstring-matching] from the [bitstring][bitstring] and recursively builds the [charlist][charlist] result.
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- Tail-recursive functions need an accumulator.
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- Remember the [bitstring special form][bitstring-form] can be used for matching on bitstrings.
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- Do not forget to specify the types of bitstring segments using the `::` operator.
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- You will need to reverse the accumulator at the end. Write a private tail-recursive `reverse` function to do that and use it in the base-case of the `decode` function.
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[integer-literal]: https://hexdocs.pm/elixir/syntax-reference.html#integers-in-other-bases-and-unicode-code-points
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[codepoint]: https://elixir-lang.org/getting-started/binaries-strings-and-char-lists.html#unicode-and-code-points
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[charlist]: https://elixir-lang.org/getting-started/binaries-strings-and-char-lists.html#charlists
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[bitstring]: https://elixir-lang.org/getting-started/binaries-strings-and-char-lists.html#bitstrings
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[bitstring-form]: https://hexdocs.pm/elixir/Kernel.SpecialForms.html#%3C%3C%3E%3E/1
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[bitstring-matching]: https://hexdocs.pm/elixir/Kernel.SpecialForms.html#%3C%3C%3E%3E/1-binary-bitstring-matching
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[type-operator]: https://hexdocs.pm/elixir/Kernel.SpecialForms.html#::/2
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[recursion-tco]: https://en.wikipedia.org/wiki/Tail_call
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[list]: https://hexdocs.pm/elixir/List.html#content
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[kernel]: https://hexdocs.pm/elixir/Kernel.html#functions
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