Grains

Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.

There once was a wise servant who saved the life of a prince. The king promised to pay whatever the servant could dream up. Knowing that the king loved chess, the servant told the king he would like to have grains of wheat. One grain on the first square of a chess board, with the number of grains doubling on each successive square.

There are 64 squares on a chessboard (where square 1 has one grain, square 2 has two grains, and so on).

Write code that shows:

• how many grains were on a given square, and
• the total number of grains on the chessboard

For bonus points

Did you get the tests passing and the code clean? If you want to, these are some additional things you could try:

• Optimize for speed.
• Optimize for readability.

Then please share your thoughts in a comment on the submission. Did this experiment make the code better? Worse? Did you learn anything from it?

Run the tests with:

bats grains_test.sh

After the first test(s) pass, continue by commenting out or removing the [[ $BATS_RUN_SKIPPED == true ]] || skip annotations prepending other tests.

To run all tests, including the ones with skip annotations, run:

BATS_RUN_SKIPPED=true bats grains_test.sh

Source

JavaRanch Cattle Drive, exercise 6 http://www.javaranch.com/grains.jsp

External utilities

Bash is a language to write "scripts" -- programs that can call external tools, such as sed, awk, date and even programs written in other programming languages, like Python. This track does not restrict the usage of these utilities, and as long as your solution is portable between systems and does not require installation of third party applications, feel free to use them to solve the exercise.

For an extra challenge, if you would like to have a better understanding of the language, try to re-implement the solution in pure Bash, without using any external tools. Note that there are some types of problems that bash cannot solve, such as performing floating point arithmetic and manipulating dates: for those, you must call out to an external tool.

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.