Fill$-$in the $3$ blank areas of code for the below ML recursive function named $rws$ that takes a string and return a new string with all whitespace removed.

fun rws $=$

if $s="$ then $""$

else if hd $($explode s$)=$ #$""$ then

else implode$($

hd $($explode s$)$ :: explode $()$

;

Hint: this code uses two ML higher$-$order functions:

explode takes a string and returns a list of characters

implode takes a list of characters and returns a string

You can test your program with the following two test data:

rws "blah foo bar"; $(*$ result should be: val it $=$ "blahfoobar": string; result should be: val it $=$ "multiplespaces": string; result should return the same string $*)$