🎉 Exercism Research is now launched. Help Exercism, help science and have some fun at research.exercism.io 🎉
Avatar of lpmatos

lpmatos's solution

to Raindrops in the Bash Track

Published at Jul 30 2020 · 1 comment
Instructions
Test suite
Solution

Your task is to convert a number into a string that contains raindrop sounds corresponding to certain potential factors. A factor is a number that evenly divides into another number, leaving no remainder. The simplest way to test if a one number is a factor of another is to use the modulo operation.

The rules of raindrops are that if a given number:

  • has 3 as a factor, add 'Pling' to the result.
  • has 5 as a factor, add 'Plang' to the result.
  • has 7 as a factor, add 'Plong' to the result.
  • does not have any of 3, 5, or 7 as a factor, the result should be the digits of the number.

Examples

  • 28 has 7 as a factor, but not 3 or 5, so the result would be "Plong".
  • 30 has both 3 and 5 as factors, but not 7, so the result would be "PlingPlang".
  • 34 is not factored by 3, 5, or 7, so the result 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 FizzBuzz, a famous technical interview question that is intended to weed out potential candidates. That question is itself derived from Fizz Buzz, a popular children's game for teaching division. https://en.wikipedia.org/wiki/Fizz_buzz

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

# Make script exit when there is an error
set -o errexit

# Main function
function main(){
  if ! [[ $1 =~ ^[0-9]+$ ]]; then echo "We need a number" && exit 1; fi
  local THREE=$(expr $1 % 3) FIVE=$(expr $1 % 5) SEVEN=$(expr $1 % 7) RESULT=""
  [ $THREE -eq 0 ] && RESULT+="Pling"
  [ $FIVE -eq 0 ] && RESULT+="Plang"
  [ $SEVEN -eq 0 ] && RESULT+="Plong"
  echo ${RESULT:-$1}
}

main "$@"

Community comments

Find this solution interesting? Ask the author a question to learn more.
Avatar of lpmatos
Solution Author
commented 52 days ago

Using bash we have different ways to concate string.

  1. Append to variable

The syntax += may be used in different ways... Concate string is one of them.

var="Hello"
var+=" World"
echo $var -> Hello World
  1. Using the Stack Overflow question syntax
var="Hello"
printf -v var "%s World" $var
echo $var -> Hello World
  1. Basically
var="Hello"
var="$varWorld"
echo $var -> Hello World
  1. Formatted, using forked printf
var="Hello"
var=$(printf "%s World" "$var")
echo $var -> Hello World
(edited 52 days ago)

lpmatos's Reflection

In this solution I worked with the mod operator and string concanetation using bash