5-8-Functions.md

5.8 Functions

5.8.4 Exercises

Below this list of exercises you can find examples of how these programs should work when used on the command line.

1. Write a function called plier which multiplies together a sequence of numbers.

2. Write a function called isiteven that prints 1 if a number is even or 0 a number is not even.

3. Write a function called nevens which prints the number of even numbers when provided with a sequence of numbers. Use isiteven when writing this function.

4. Write a function called howodd which prints the percentage of odd numbers in a sequence of numbers. Use nevens when writing this function.

5. Write a function called fib which prints the number of fibonacci numbers specified.

$ plier 7 2 3

## 42

$ isiteven 42

## 1

$ nevens 42 6 7 9 33

## 2

$ howodd 42 6 7 9 33

## .60

$ fib 4

## 0 1 1 2

$ fib 10

## 0 1 1 2 3 5 8 13 21 34

---

Solutions

1. plier

   #!usr/bin/env bash
   # File: ex5-8-q1.sh
   
   function plier
   {
       local res=1
   
       for num in $@
       do
           let res=$res\*$num
       done
   
       echo $res
   }
   
   # Test:
   # Method 1:
   # Uncomment the next line here and run the script using bash
   # plier $@
   
   # Method 2:
   # Write the next line in the command line then call 
   # the function name with arbitrary arguments
   # source ex5-8-q1.sh

2. isiteven

   #!usr/bin/env bash
   # File: ex5-8-q2.sh
   
   function isiteven
   {
       [[ $1%2 -eq 0 ]] && echo 1 || echo 0
   }
   
   # Test:
   # Method 1:
   # Uncomment the next line here and run the script using bash
   # isiteven $1
   
   # Method 2:
   # Write the next line in the command line then call 
   # the function name with arbitrary arguments
   # source ex5-8-q2.sh

3. nevens

   #!usr/bin/env bash
   # File: ex5-8-q3.sh
   
   function neven
   {
       local sum=0
   
       for num in $@
       do
           let sum=$sum+$(isiteven $num)
       done
   
       echo $sum
   }
   
   # Test:
   # Method 1:
   # Uncomment the next line here and run the script using bash
   # neven $@
   
   # Method 2:
   # Write the next line in the command line then call 
   # the function name with arbitrary arguments
   # source ex5-8-q3.sh

4. howodd

   #!usr/bin/env bash
   # File: ex5-8-q4.sh
   
   function howodd
   {
       howeven=$(neven $@)
   
       printf "%.2f\n" $(echo 1.0 - $howeven / $# | bc -l)
   }
   
   # Test:
   # Method 1:
   # Uncomment the next line here and run the script using bash
   # howodd $@
   
   # Method 2:
   # Write the next line in the command line then call 
   # the function name with arbitrary arguments
   # source ex5-8-q4.sh

5. fib

   #!usr/bin/env bash
   # File: ex5-8-q5.sh
   
   function fib
   {
       if [[ $1 -eq 1 ]]
       then
           echo 0
       elif [[ $1 -eq 2 ]]
       then
           echo 0 1
       else
           # Starting elements of the series
           local arr=(0 1)
   
           # Number of elements to be added to the series
           local end=$(expr $1 - 2)
   
           # Local variable of the current element to be added
           local element=0
   
           # Iterate 'end' times
           for i in $(eval echo {1..$end})
           do
               # element = last + 2nd_last
               let element=${arr[-1]}+${arr[-2]}
               
               # element becomes the new last
               arr+=($element)
           done
   
           echo ${arr[*]}
       fi      
   }
   
   # Test:
   # Method 1:
   # Uncomment the next line here and run the script using bash
   # fib $1
   
   # Method 2:
   # Write the next line in the command line then call 
   # the function name with arbitrary arguments
   # source ex5-8-q5.sh