Matthieu Pizenberg (Jun 11 2024 at 18:21): Matthieu Pizenberg (Jun 11 2024 at 18:21):What is the simplest way to format U8 numbers into hex strings? For example, convert 255 into "ff"
Matthieu Pizenberg (Jun 11 2024 at 18:34):I went with this since I didn’t found any obvious function from std:
hex : U8 -> Str
hex = \n ->
high = Num.shiftRightZfBy n 4
low = Num.bitwiseAnd n 0x0f
Str.concat (u4Hex high) (u4Hex low)
u4Hex : U8 -> Str
u4Hex = \n ->
when n is
0 -> "0"
1 -> "1"
2 -> "2"
3 -> "3"
4 -> "4"
5 -> "5"
6 -> "6"
7 -> "7"
8 -> "8"
9 -> "9"
10 -> "a"
11 -> "b"
12 -> "c"
13 -> "d"
14 -> "e"
15 -> "f"
_ -> crash "n should be < 16"
u8ToHexStr : List U8 -> Str
u8ToHexStr = \bytes ->
List.map bytes \byte ->
b1 = byte // 16 |> \b -> if b >= 10 then b + 87 else b + 48
b2 = byte % 16 |> \b -> if b >= 10 then b + 87 else b + 48
Str.fromUtf8 [b1, b2] |> Result.withDefault "00"
|> Str.joinWith ""
u4Hex = \n -> if n >= 10 then n - 10 + 'a' else n + '0'
This maybe?
Ian McLerran (Jun 11 2024 at 18:49):Yeah, thats even better. Much clearer to the reader.
Then just: `Str.fromUtf8 [(u4Hex high), (u4Hex low)] |> Result.withDefault "00"
Notification Bot (Jun 11 2024 at 20:04):Matthieu Pizenberg has marked this topic as resolved.
Last updated: Jul 26 2025 at 12:14 UTC