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# Hamming
Calculate the Hamming Distance between two DNA strands.
Your body is made up of cells that contain DNA. Those cells regularly wear out and need replacing, which they achieve by dividing into daughter cells. In fact, the average human body experiences about 10 quadrillion cell divisions in a lifetime!
When cells divide, their DNA replicates too. Sometimes during this process mistakes happen and single pieces of DNA get encoded with the incorrect information. If we compare two strands of DNA and count the differences between them we can see how many mistakes occurred. This is known as the "Hamming Distance".
We read DNA using the letters C,A,G and T. Two strands might look like this:
GAGCCTACTAACGGGAT
CATCGTAATGACGGCCT
^ ^ ^ ^ ^ ^^
They have 7 differences, and therefore the Hamming Distance is 7.
The Hamming Distance is useful for lots of things in science, not just biology, so it's a nice phrase to be familiar with :)
# Implementation notes
The Hamming distance is only defined for sequences of equal length, so
an attempt to calculate it between sequences of different lengths should
not work. The general handling of this situation (e.g., raising an
exception vs returning a special value) may differ between languages.
## Resources
Remember to check out the Raku [documentation](https://docs.raku.org/) and
[resources](https://raku.org/resources/) pages for information, tips, and
examples if you get stuck.
## Running the tests
There is a test suite and module included with the exercise.
The test suite (a file with the extension `.rakutest`) will attempt to run routines
from the module (a file with the extension `.rakumod`).
Add/modify routines in the module so that the tests will pass! You can view the
test data by executing the command `raku --doc *.rakutest` (\* being the name of the
test suite), and run the test suite for the exercise by executing the command
`prove6 .` in the exercise directory.
## Source
The Calculating Point Mutations problem at Rosalind [http://rosalind.info/problems/hamm/](http://rosalind.info/problems/hamm/)
## Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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