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kiwike's solution

to Raindrops in the Bash Track

Published at Aug 02 2020 · 0 comments
Instructions
Test suite
Solution

Convert a number to a string, the contents of which depend on the number's factors.

  • If the number has 3 as a factor, output 'Pling'.
  • If the number has 5 as a factor, output 'Plang'.
  • If the number has 7 as a factor, output 'Plong'.
  • If the number does not have 3, 5, or 7 as a factor, just pass the number's digits straight through.

Examples

  • 28's factors are 1, 2, 4, 7, 14, 28.
    • In raindrop-speak, this would be a simple "Plong".
  • 30's factors are 1, 2, 3, 5, 6, 10, 15, 30.
    • In raindrop-speak, this would be a "PlingPlang".
  • 34 has four factors: 1, 2, 17, and 34.
    • In raindrop-speak, this would be "34".

Run the tests with:

bats raindrops_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 raindrops_test.sh

Source

A variation on a famous interview question intended to weed out potential candidates. http://jumpstartlab.com

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.

raindrops_test.sh

#!/usr/bin/env bash

# local version: 1.1.0.0

@test "the sound for 1 is 1" {
  #[[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 1
  (( status == 0 ))
  [[ $output == "1" ]]
}

@test "the sound for 3 is Pling" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 3
  (( status == 0 ))
  [[ $output == "Pling" ]]
}

@test "the sound for 5 is Plang" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 5
  (( status == 0 ))
  [[ $output == "Plang" ]]
}

@test "the sound for 7 is Plong" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 7
  (( status == 0 ))
  [[ $output == "Plong" ]]
}

@test "the sound for 6 is Pling as it has a factor 3" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 6
  (( status == 0 ))
  [[ $output == "Pling" ]]
}

@test "2 to the power 3 does not make a raindrop sound as 3 is the exponent not the base" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 8
  (( status == 0 ))
  [[ $output == "8" ]]
}

@test "the sound for 9 is Pling as it has a factor 3" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 9
  (( status == 0 ))
  [[ $output == "Pling" ]]
}

@test "the sound for 10 is Plang as it has a factor 5" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 10
  (( status == 0 ))
  [[ $output == "Plang" ]]
}

@test "the sound for 14 is Plong as it has a factor of 7" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 14
  (( status == 0 ))
  [[ $output == "Plong" ]]
}

@test "the sound for 15 is PlingPlang as it has factors 3 and 5" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 15
  (( status == 0 ))
  [[ $output == "PlingPlang" ]]
}

@test "the sound for 21 is PlingPlong as it has factors 3 and 7" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 21
  (( status == 0 ))
  [[ $output == "PlingPlong" ]]
}

@test "the sound for 25 is Plang as it has a factor 5" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 25
  (( status == 0 ))
  [[ $output == "Plang" ]]
}

@test "the sound for 27 is Pling as it has a factor 3" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 27
  (( status == 0 ))
  [[ $output == "Pling" ]]
}

@test "the sound for 35 is PlangPlong as it has factors 5 and 7" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 35
  (( status == 0 ))
  [[ $output == "PlangPlong" ]]
}

@test "the sound for 49 is Plong as it has a factor 7" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 49
  (( status == 0 ))
  [[ $output == "Plong" ]]
}

@test "the sound for 52 is 52" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 52
  (( status == 0 ))
  [[ $output == "52" ]]
}

@test "the sound for 105 is PlingPlangPlong as it has factors 3, 5 and 7" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 105
  (( status == 0 ))
  [[ $output == "PlingPlangPlong" ]]
}

@test "the sound for 3125 is Plang as it has a factor 5" {
  [[ $BATS_RUN_SKIPPED == "true" ]] || skip
  run bash raindrops.sh 3125
  (( status == 0 ))
  [[ $output == "Plang" ]]
}
#!/usr/bin/env bash

main () {
    local out
    (( $1 % 3 == 0 )) && out+='Pling'
    (( $1 % 5 == 0 )) && out+='Plang'
    (( $1 % 7 == 0 )) && out+='Plong'
    [[ -z $out ]] && out=$1
    echo "$out"
}

main "$@"

What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?