Chapter 1 #520
Chapter 1 #520
Conversation
| @@ -490,7 +490,8 @@ Implement a function that returns the last digit of a given number. | |||
| whether it works for you! | |||
| -} | |||
| -- DON'T FORGET TO SPECIFY THE TYPE IN HERE | |||
| lastDigit n = error "lastDigit: Not implemented!" | |||
| lastDigit :: Int -> Int | |||
| lastDigit x = mod x 10 | |||
There was a problem hiding this comment.
Your implementation is almost correct 🆗
Unfortunately, it returns negative numbers on negative inputs because of how mod works. Sometimes corner cases can be tricky to spot and fix...
| sumLast2 n = let last = mod n 10 | ||
| seclast = mod (div n 10) 10 -- div n 10 gives the digit stripped off last digit. |
There was a problem hiding this comment.
That is a wonderful solution! 👏🏼 You correctly noticed that it is the div and mod, cool 😎
One hint to make your solution even shorter: you can see that you use both:
mod m 10
div m 10The standard library has the divMod function, that actually combines inside both div and mod. And this is exactly what you use!.
So you could write it this way:
(x, y) = divMod m 10You can see how we could pattern match on the pair 🙂
| firstDigit n = error "firstDigit: Not implemented!" | ||
|
|
||
| firstDigit :: Int -> Int | ||
| firstDigit n = if n < 10 then n else firstDigit (div n 10) |
There was a problem hiding this comment.
I see, that for a negative number like -19, this implementation will return the negative number itself instead of the last digit because the first check n < 10 will always succeed for negative numbers.
vrom911
added
chapter1
hacktoberfest-accepted
Solutions for Chapter 1
cc @vrom911 @chshersh