Coding Kata

•How to improve your technical skills

through deliberate practice

•Cezar Coca, Silviu Eigel

•12/14/2011

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Kata

• Kata (形, or more traditionally, 型) (literally: "form")

is a Japanese word describing detailed patterns of

movements practiced either solo or in pairs. Karate

Kata are executed as a specified series of a variety of

moves, with stepping and turning, while attempting

to maintain perfect form.

• A code kata is an exercise in programming which

helps a programmer hone their skills through

practice and repetition.

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Deliberate Practice

•Done over a long period of time is at the heart of attaining expertise (10k hours)

•Different than experience gained while doing your job (pressure-free)

• Learning through Deliberate Practice requires:

• A state of discomfort

• A lot of self discipline

• Exposing your weaknesses

• Exposing yourself to other people’s tricks

• Seeking out experiences that stretch your skills and give you feedback

•Musicians do it through the practice of scales and arpeggios. So do martial arts experts

• I’ve been intending to sit down and do a kata for as long as I know of them

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What we will practice – TDD

• Test-driven development (TDD) is a software development technique that relies on the

repetition of a very short development cycle

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What we will practice – Pair Programming

• It's more fun and less expensive than it sounds: two programmers at one computer

•One drives; the other navigates. Switching roles fluidly, they constantly communicate.

Together, they accomplish better work more quickly than either could alone.

• The driver types

• He focuses on tactics--writing clean code that compiles and runs

• The navigator focuses on strategy

• How the code fits into the overall design

• Which tests will drive the code forward

• Which refactoring will improve the entire codebase

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String Calculator Kata

• Create a simple String calculator with a method int Add(string numbers)

• The method can take 0, 1 or 2 numbers, and will return their sum (for an empty string it will return 0) for

example “” or “1” or “1,2”

• Start with the simplest test case of an empty string and move to 1 and two numbers

• Remember to solve things as simply as possible so that you force yourself to write tests you did not think about

• Remember to refactor after each passing test

• Allow the Add method to handle an unknown amount of numbers

• Allow the Add method to handle new lines between numbers (instead of commas).

• the following input is ok: “1\n2,3” (will equal 6)

• the following input is NOT ok: “1,\n” (not need to prove it - just clarifying)

• Support different delimiters to change a delimiter, the beginning of the string will contain a separate line that

looks like this: “//[delimiter]\n[numbers…]” for example “//;\n1;2” should return three where the default

delimiter is ‘;’ .

• the first line is optional. all existing scenarios should still be supported

• Calling Add with a negative number will throw an exception “negatives not allowed” - and the negative that was

passed. If there are multiple negatives, show all of them in the exception message

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thank you

Cezar Coca, Silviu EigelGeeks