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Anyone here use assembly? (lemm.ee)

submitted 3 months ago* (last edited 3 months ago) by [email protected] to c/[email protected]

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[–] [email protected] 49 points 3 months ago (4 children)

Assembly code is for writing C compilers, and C compilers are for writing Lisp interpreters.

[–] [email protected] 21 points 3 months ago (1 children)

I saw a Scheme interpreter written in assembly running a C compiler written in Scheme.

[–] [email protected] 31 points 3 months ago (1 children)

[–] [email protected] 5 points 3 months ago* (last edited 3 months ago)

There’s actually good reasons for this design. It’s easy to write a Scheme interpreter in assembly, but it’s hard to write a C compiler in assembly that handles everything correctly. Much rather write it in higher level language if possible and Scheme lowers the bar to getting there, so you can get away from using assembly as quickly as possible. Or you can copy somebody else’s Scheme implementation of a C compiler because now you’re platform independent.

Then you can write your C compiler in C (or steal a better compiler already written in C) and close the loop. For your final step, you use the C compiler to compile itself.

[–] [email protected] 15 points 3 months ago* (last edited 3 months ago) (3 children)

Only the most very basic compilers. C compilers are in C mainly.

[–] [email protected] 11 points 3 months ago* (last edited 3 months ago)

Not the first C compiler obviously. According to this Stack Overflow post, BCPL* begat B, which begat C. Language self-hosting is pretty fascinating.

*Perhaps BCPL was originally written in assembly; I’m not certain: https://github.com/SergeGris/BCPL-compiler

[–] [email protected] 8 points 3 months ago (1 children)

Talking about bootstrap here?

[–] [email protected] 2 points 3 months ago

Indeed

[–] [email protected] 2 points 3 months ago

And that's how you get the Thompson hack

[–] [email protected] 4 points 3 months ago (1 children)

Back in High School in the 80’s me and a buddy wrote a Z-80 editor assembler in TRS-DOS BASIC.

It was not rocket science.

[–] [email protected] 5 points 3 months ago* (last edited 3 months ago)

I never did get very far with the TRS-80 Editor Assembler, but that was my first exposure to such things.

I also remember the BASIC code for the Dancing Daemon which was replete with PEEKs and POKEs, such that much of it was written in machine code.