This is over my head. Why did we need to take a trip to discover why \n is encoded as a byte with the value 10? Isn't that expected? The author and HN comments don't say, so I feel stupid.
The ultimate point of this exercise is to alter your perception of what a compiler is (in the same way as the famous Reflections On Trusting Trust presentation).
Which is to say: your compiler is not something that outputs your program; your compiler is also input to your program. And as a program itself, your compiler's compiler was an input to your compiler, which makes it transitively an input to your program, and the same is true of your compiler's compiler's compiler, and your compiler's compiler's compiler's compiler, and your compiler's compiler's compiler's compiler's compiler, and...
It's an interesting real-world example of the Ken Thompson hack.
As a human I can just Google "C string escape codes", but that table is nowhere to be found inside the compiler. If C 2025 is going to define Start of Heading as \h, is `'h' => cooked.push('\h')` going to magically start working? How could it possibly know?
Clearly at some point someone must've manually programmed a `'n' => 10` mapping, but where is it!?
You can look into the ascii table then.
10 is the line feed. '\n' is there to help human because it makes more sense than '10'.
Nobody is asking why 'a' is equal to '61'.
From the codebase, you know that '\n' is a char. A char is a value between 0 and 255, if you explicitly convert '\n' to int then you happen to find the ascii value and you are good to go and there is no need to pretend there is any poetry in this.
Requoting you:
> "if you see 'string of newline character', output 'newline character'"
It simply becomes "if a you see 'the arbitrary symbol for the new line', output 'the corresponding ascii value'".
I read the quote as "if you see 'a', output 'a' in ascii code." which is not mysterious in any kind of way.
IMO, the article does not make sense at all because it pretends to wonder where an hexadecimal value is coming from, but with any other kind of symbol it would be the exact same article, you enter 'a' and find some weird hexadecimal value and you won't be able to correctly trace it from the source code.
It would make sense it 'a' would display 'a' but '\n' would display some hexadecimal garbage in a text editor.
But how does the computer know which int to output when you "explicitly convert '\n' to int"? As humans, we can clearly just consult the ASCII table and/or the relevant language standard, but the computer doesn't have a brain and a pair of eyes, instead it must store that association somewhere. The purpose of this article is to locate where the association was originally entered into the source code by some human.
The question is less interesting for ordinary characters like 'a', since the codes for those are presumably baked into the keyboard hardware and the font files, and no further translation is needed.
It's true that the question is less interesting for regular characters, but your explanation why is way off base.
Consider a computer whose only I/O is a serial console. It is concerned with neither a keyboard nor a font file.
That is, suppose I design a font file so that character 0x61 has glyph 'b' and 0x62 has glyph 'a', and I accordingly swap the key caps for 'A' and 'B' on my keyboard. If I write a document with this font file and print it off, then no one looking at it could tell that my characters had the wrong codes. Only the spell-checker on my computer would complain, since it's still following its designers' ideas of the character codes 0x61 and 0x62 are supposed to mean within a word.
But physical computers knew what to insert in place immediately, because there was 0x0a somewhere in binary every time.
> I read the quote as "if you see 'a', output 'a' in ascii code." which is not mysterious in any kind of way.
Only, it's not like that.
It's like:
> If you see a backslash followed by n, output a newline.
There's no 'newline character' in the input we are parsing here.
I suggest reading the article, to find out just how badly you’re missing the point.
Check the first Unicode codepoints, 10 is defined there:
000A is LINE FEED (LF) = new line (NL), end of line (EOL)
It was already 10 in ASCII too (and the first 128 codepoints of Unicode are mostly the same as ASCII [I think there are a few tiny differences in some control characters]).
So to answer your question: it's neither 9 nor 11 because '\n' stands for "new line" and not for "character tabulation" nor for "line tabulation" (which 9 and 11 respectively stands for).
> Clearly at some point someone must've manually programmed a `'n' => 10` mapping
I don't disagree with that.
The point is how the compiler knows that. Read the article.