> Lua's stack protocol can sometimes be verbose, but I find it infinitely more simple and elegant than the existing alternatives.
This. TL;DNR, used a C/Lua binding to explain the Lua stack to a fellow engineer. Took a few post-it notes to keep track of 4 levels of stack, 1 pcall back to Lua to sort an array, and forward the results on. It just worked, was elegant, and blew our minds.
Today on Friday at 5pm I was talking about a ‘problem’ we had with a Lua daemons compared to their C brothers. Due to the use of tables, each time you queried them, the output order was always random. Computers don’t care, but a big user is also engineers and finding fields wandering all over the place is a pita. So what if we ordered the keys alphabetically instead? The code is Lua -> C -> IPC -> Output. The order is set in the Lua->C binding, so what if we sorted it in the binding.
But the tables are arbitrary size and you’d have to allocate memory, put them in a structure of some kind, etc, etc. Then we realized we could just put all the keys in a Lua array, and sort them with table.sort(). We could then use the array to get key/values in order, all from within the C binding.
Being late Friday, and having talked it through let’s just do it. Plus it was a handy teaching moment to explain to a fellow engineer how Lua binding worked, including a call back into Lua. By 6pm we had the binding recompiled, tested and it’s just worked.
Lessons learned:
1. The stack can seem confusing, but once you learn how to work with it, it’s pretty amazing.
2. The Lua reference docs are amazing. They clearly list what they pop and what they push onto the stack.
3. Calling back into Lua is.
4. It looks like write only code. Reading the code needs a post it note to keep track of the stack, along with the Lua reference manual. -- comments...
This. TL;DNR, used a C/Lua binding to explain the Lua stack to a fellow engineer. Took a few post-it notes to keep track of 4 levels of stack, 1 pcall back to Lua to sort an array, and forward the results on. It just worked, was elegant, and blew our minds.
Today on Friday at 5pm I was talking about a ‘problem’ we had with a Lua daemons compared to their C brothers. Due to the use of tables, each time you queried them, the output order was always random. Computers don’t care, but a big user is also engineers and finding fields wandering all over the place is a pita. So what if we ordered the keys alphabetically instead? The code is Lua -> C -> IPC -> Output. The order is set in the Lua->C binding, so what if we sorted it in the binding.
But the tables are arbitrary size and you’d have to allocate memory, put them in a structure of some kind, etc, etc. Then we realized we could just put all the keys in a Lua array, and sort them with table.sort(). We could then use the array to get key/values in order, all from within the C binding.
Being late Friday, and having talked it through let’s just do it. Plus it was a handy teaching moment to explain to a fellow engineer how Lua binding worked, including a call back into Lua. By 6pm we had the binding recompiled, tested and it’s just worked.
Lessons learned:
1. The stack can seem confusing, but once you learn how to work with it, it’s pretty amazing.
2. The Lua reference docs are amazing. They clearly list what they pop and what they push onto the stack.
3. Calling back into Lua is.
4. It looks like write only code. Reading the code needs a post it note to keep track of the stack, along with the Lua reference manual. -- comments...