From 078eca583eec21d317e931c84db8f084bef4305d Mon Sep 17 00:00:00 2001
From: Elizabeth Alexander Hunt <me@liz.coffee>
Date: Wed, 22 Apr 2026 15:58:41 -0700
Subject: Snapshot

---
 util.lua | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 util.lua

(limited to 'util.lua')

diff --git a/util.lua b/util.lua
new file mode 100644
index 0000000..bb9b2e8
--- /dev/null
+++ b/util.lua
@@ -0,0 +1,52 @@
+-- https://pico-8.fandom.com/wiki/Qsort
+function qsort(a,c,l,r)
+	c,l,r=c or function(a,b) return a<b end,l or 1,r or #a
+	if l<r then
+		if c(a[r],a[l]) then
+			a[l],a[r]=a[r],a[l]
+		end
+		local lp,k,rp,p,q=l+1,l+1,r-1,a[l],a[r]
+		while k<=rp do
+			local swaplp=c(a[k],p)
+			-- "if a or b then else"
+			-- saves a token versus
+			-- "if not (a or b) then"
+			if swaplp or c(a[k],q) then
+			else
+				while c(q,a[rp]) and k<rp do
+					rp-=1
+				end
+				a[k],a[rp],swaplp=a[rp],a[k],c(a[rp],p)
+				rp-=1
+			end
+			if swaplp then
+				a[k],a[lp]=a[lp],a[k]
+				lp+=1
+			end
+			k+=1
+		end
+		lp-=1
+		rp+=1
+		-- sometimes lp==rp, so 
+		-- these two lines *must*
+		-- occur in sequence;
+		-- don't combine them to
+		-- save a token!
+		a[l],a[lp]=a[lp],a[l]
+		a[r],a[rp]=a[rp],a[r]
+		qsort(a,c,l,lp-1       )
+		qsort(a,c,  lp+1,rp-1  )
+		qsort(a,c,       rp+1,r)
+	end
+    return a
+end
+
+function filter(a, pred)
+    filtered = {}
+    for k,v in ipairs(a) do
+        if pred(v) then
+            filtered[k] = v
+        end
+    end
+    return filtered
+end
\ No newline at end of file
-- 
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