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