From 6e8f6e9ef3eb7ec20134be17255bfb074e8421f0 Mon Sep 17 00:00:00 2001
From: Niklas Heim <heim.niklas@gmail.com>
Date: Fri, 23 Feb 2024 07:51:58 +0100
Subject: [PATCH] Solution to Lab 01 (#5)

---
 labs/lab01.md | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/labs/lab01.md b/labs/lab01.md
index 051726c..4ad5a0e 100644
--- a/labs/lab01.md
+++ b/labs/lab01.md
@@ -130,16 +130,14 @@ The number of digits can be computed by successive dividing the input number by
 the integer division, you can use the function `quotient`.
 :::
 
-<!--
 ::: details Solution
 ```scheme
 (define (num-of-digits n [acc 1])
-  (cond [(< n 0) (num-of-digits (- n))]
-        [(< n 10) acc]
-        [else (num-of-digits (quotient n 10) (+ acc 1))]))
+  (define q (quotient n 10))
+  (if (= q 0) acc (num-of-digits q (+ acc 1))))
 ```
+Thank you for the improved solution <u>@Denis Pak</u>!
 :::
--->
 
 ### Task 2
 Write a function `(num->str n [radix 10])` taking as input an integer `n` together
@@ -159,7 +157,6 @@ remainders. The remainder after integer division can be computed by the function
 :::
 
 
-<!--
 ::: details Solution
 ```scheme
 (define (num->str n [radix 10])
@@ -174,18 +171,21 @@ remainders. The remainder after integer division can be computed by the function
       rem-str
       (string-append (num->str (quotient n radix) radix)
                      rem-str)))
+```
 
-; Alternative
-#|
+Alternatively, you can use `string-ref` to pick out the correct character from `numeric-alphabet`
+given an index, and instead of `string-append`ing you can construct a list of characters which is
+converted to a string in the end:
+```scheme
 (define numeric-alphabet "0123456789ABCDEF")
+
 (define (num->char n [radix 10])
   (string-ref numeric-alphabet (remainder n radix)))
+
 (define (num->str n [radix 10] [acc '()])
   (cond
     [(negative? n) (num->str (- n) radix '(#\-))]
     [(< n radix) (list->string (cons (num->char n radix) acc))]
     [else (num->str (quotient n radix) radix (cons (num->char n radix) acc))]))
-|#
 ```
-:::-->
-
+:::