This thread isn't the first time I've seen people ask about inserting values into the middle or start of arrays/sequences:
It occurs to me that a lot of carts probably have similar boilerplate code like the ins() function I wrote for that person. I think it would be nice, and better for PICO-8's host-machine performance, if there were a C-side implementation of that insert code, and I think you could do it simply by taking an optional third argument to add(), effectively implementing something like this Lua code on the C side:
function add(t,v,i) i=i or #t+1 -- default to extending the list for j=#t,i,-1 do t[j+1]=t[j] end t[i]=v return v -- return the added value for convenience end
This shouldn't break any existing code, since there hasn't previously been a third arg, and the default value produces the existing behavior.
(Come to think of it, I'm not sure if you have add() on the C side or as hidden Lua. If it's not already on the C side, you might want to put it there, because it happens a lot in carts and doing it through interpreted code is definitely going to slow things down on the host hardware. Same goes for any other oft-called hidden Lua code.)
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