From b1e2961e1df83c55f79d0f7d5cf924256252e213 Mon Sep 17 00:00:00 2001
From: Rose Hogenson <rosehogenson@posteo.net>
Date: Sun, 27 Aug 2023 18:01:10 -0700
Subject: Write a god-awful Mandelbrot set program.

---
 .gitignore    |  1 +
 flake.lock    | 25 ++++++++++++++++
 flake.nix     | 17 +++++++++++
 go.mod        |  7 +++++
 go.sum        |  4 +++
 mandelbrot.go | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 147 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 flake.lock
 create mode 100644 flake.nix
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 mandelbrot.go

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..c4a847d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/result
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..a928af0
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,25 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1693145325,
+        "narHash": "sha256-Gat9xskErH1zOcLjYMhSDBo0JTBZKfGS0xJlIRnj6Rc=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "cddebdb60de376c1bdb7a4e6ee3d98355453fe56",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..1b1fb35
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,17 @@
+{
+  outputs = { self, nixpkgs }:
+  let pkgs = nixpkgs.legacyPackages.x86_64-linux; in
+  rec {
+
+    packages.x86_64-linux.mandelbrot = pkgs.buildGoModule {
+      pname = "mandelbrot";
+      version = "1.0";
+
+      src = self;
+
+      vendorHash = "sha256-WiEK8nq13mdTFnyxDiMRWM1tb60mlZY0fVmtlH5ZWgw=";
+    };
+
+    defaultPackage.x86_64-linux = packages.x86_64-linux.mandelbrot;
+  };
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..8e82360
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,7 @@
+module mandelbrot
+
+go 1.20
+
+require golang.org/x/term v0.11.0
+
+require golang.org/x/sys v0.11.0 // indirect
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..6aed7b2
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,4 @@
+golang.org/x/sys v0.11.0 h1:eG7RXZHdqOJ1i+0lgLgCpSXAp6M3LYlAo6osgSi0xOM=
+golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.11.0 h1:F9tnn/DA/Im8nCwm+fX+1/eBwi4qFjRT++MhtVC4ZX0=
+golang.org/x/term v0.11.0/go.mod h1:zC9APTIj3jG3FdV/Ons+XE1riIZXG4aZ4GTHiPZJPIU=
diff --git a/mandelbrot.go b/mandelbrot.go
new file mode 100644
index 0000000..27d7bdb
--- /dev/null
+++ b/mandelbrot.go
@@ -0,0 +1,93 @@
+package main
+
+import (
+	"fmt"
+	"golang.org/x/term"
+	"log"
+	"math/big"
+	"time"
+)
+
+type color int
+
+const (
+	black color = iota
+	red
+	yellow
+	green
+	cyan
+	blue
+	magenta
+)
+
+func (c color) print() {
+	var i int
+	switch c {
+	case red:
+		i = 41
+	case yellow:
+		i = 43
+	case green:
+		i = 42
+	case cyan:
+		i = 46
+	case blue:
+		i = 44
+	case magenta:
+		i = 45
+	default:
+		i = 40
+	}
+	if _, err := fmt.Printf("\033[%dm ", i); err != nil {
+		log.Fatal(err)
+	}
+}
+
+var rat2 = big.NewRat(2, 1)
+
+func mandelbrot(x0, y0 *big.Rat) color {
+	x := new(big.Rat)
+	y := new(big.Rat)
+	x2 := new(big.Rat)
+	y2 := new(big.Rat)
+	i := 0
+	for ; x2.Cmp(rat2) <= 0 && y2.Cmp(rat2) <= 0; i++ {
+		y.Add(y, y).Mul(y, x).Add(y, y0)
+		x.Sub(x2, y2).Add(x, x0)
+		x2.Mul(x, x)
+		y2.Mul(y, y)
+	}
+	return color(i-1)%magenta + 1
+}
+
+func printMandelbrot(xMin, xRange, yMin, yRange *big.Rat) {
+	width, height, err := term.GetSize(0)
+	if err != nil {
+		log.Fatalf("Terminal size: %s.", err)
+	}
+
+	xStep := new(big.Rat).Quo(xRange, big.NewRat(int64(width), 1))
+	yStep := new(big.Rat).Quo(yRange, big.NewRat(int64(height), 1))
+	grid := make([]color, width*height)
+	y := new(big.Rat)
+	x := new(big.Rat)
+	y.Set(yMin)
+	for i := 0; i < height; i++ {
+		x.Set(xMin)
+		for j := 0; j < width; j++ {
+			go func(i, j int, x, y *big.Rat) {
+				grid[i*width+j] = mandelbrot(x, y)
+			}(i, j, new(big.Rat).Set(x), new(big.Rat).Set(y))
+			x.Add(x, xStep)
+		}
+		y.Add(y, yStep)
+	}
+	time.Sleep(time.Minute)
+	for _, c := range grid {
+		c.print()
+	}
+}
+
+func main() {
+	printMandelbrot(big.NewRat(-3, 2), big.NewRat(247, 100), big.NewRat(-112, 100), big.NewRat(224, 100))
+}
-- 
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