4 ms·

This is pretty cool. What are the use cases?

wdpk 2y ago
compile c++ code at runtime for instance. Lots of use cases, most obvious one specializing/instantiating dense computational kernels on values only known at runtime... but so many more things would be possible if the compiler was just a reusable library.
- ska 2y ago
  This is something Common Lisp got really right.
  - wdpk 2y ago
    well being homoiconic and dynamic helps quite a bit... This being said, if you squint a bit and get used to the syntax, c++ variadic templates are just a compile-time lisp (really templates are just generalized functions over types) and the template mechanism is 100% pure, with a runtime capability of evaluating those pure monadic computational effects defined at compile-time to runtime, there is no more boundary (not saying it's a thing that should be done all the time). The main advantage then over functional languages is the fact that c++ optimizing compilers are already pretty good at optimization so assuming that you can afford to re-compile at runtime the tight inner loops or critical paths (say at "configuration time" when adding some latency might not be a big deal), a lot of otherwise impossible optimizations could probably be done better (thinking of loop invariants, polyhedral, unrolling, constant propagation, aliasing, row major to column major etc etc) probably the result would also be better than what a JIT compiler and profiler would be able to achieve too.
    - gpderetta 2y ago
      > template mechanism is 100% pure Let's say 99.99%. You underestimate the resourcefulness of C++ (meta-)programmers and their ability to leverage implementations or specification bugs for "useful" purposes: https://b.atch.se/posts/non-constant-constant-expressions/ https://b.atch.se/posts/non-constant-constant-expressions/
yuserx 2y ago
~22MB download for a full IDE https://www.kvraudio.com/forum/viewtopic.php?t=560622 https://www.kvraudio.com/forum/viewtopic.php?t=560622
menaerus 2y ago
REPL and JIT come to mind.
secondcoming 2y ago
I’ve wanted something like this to compile XML business rules to native code on the fly. I would have a script that converted the XML to C and then turn that into machine code that I’d load directly from the .text section of the binary (shellcode style). Turns out this is error prone because compilers can emit things like jump tables into the .rodata section, so you need that too. It’s easier to just create a shared library.
- high_na_euv 2y ago
  XML business rules? Is it xml-oriented-programming again? They were doing it in Java 25 years ago
mshockwave 2y ago
I think this is exactly how Zig compiler does under the hood for C/C++ sources. So I guess you can do a similar thing for your own programming languages to support interop.

wdpk 2y ago

compile c++ code at runtime for instance. Lots of use cases, most obvious one specializing/instantiating dense computational kernels on values only known at runtime... but so many more things would be possible if the compiler was just a reusable library.

ska 2y ago
This is something Common Lisp got really right.
- wdpk 2y ago
  well being homoiconic and dynamic helps quite a bit... This being said, if you squint a bit and get used to the syntax, c++ variadic templates are just a compile-time lisp (really templates are just generalized functions over types) and the template mechanism is 100% pure, with a runtime capability of evaluating those pure monadic computational effects defined at compile-time to runtime, there is no more boundary (not saying it's a thing that should be done all the time). The main advantage then over functional languages is the fact that c++ optimizing compilers are already pretty good at optimization so assuming that you can afford to re-compile at runtime the tight inner loops or critical paths (say at "configuration time" when adding some latency might not be a big deal), a lot of otherwise impossible optimizations could probably be done better (thinking of loop invariants, polyhedral, unrolling, constant propagation, aliasing, row major to column major etc etc) probably the result would also be better than what a JIT compiler and profiler would be able to achieve too.
  - gpderetta 2y ago
    > template mechanism is 100% pure Let's say 99.99%. You underestimate the resourcefulness of C++ (meta-)programmers and their ability to leverage implementations or specification bugs for "useful" purposes: https://b.atch.se/posts/non-constant-constant-expressions/ https://b.atch.se/posts/non-constant-constant-expressions/

yuserx 2y ago

~22MB download for a full IDE https://www.kvraudio.com/forum/viewtopic.php?t=560622 https://www.kvraudio.com/forum/viewtopic.php?t=560622

menaerus 2y ago

REPL and JIT come to mind.

secondcoming 2y ago

I’ve wanted something like this to compile XML business rules to native code on the fly. I would have a script that converted the XML to C and then turn that into machine code that I’d load directly from the .text section of the binary (shellcode style). Turns out this is error prone because compilers can emit things like jump tables into the .rodata section, so you need that too. It’s easier to just create a shared library.

high_na_euv 2y ago
XML business rules? Is it xml-oriented-programming again? They were doing it in Java 25 years ago

mshockwave 2y ago

I think this is exactly how Zig compiler does under the hood for C/C++ sources. So I guess you can do a similar thing for your own programming languages to support interop.