mjau

.envrc

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+use flake

.gitignore

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+target/
+.direnv

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "primes"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "primes"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

flake.lock

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+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1726560853,
+        "narHash": "sha256-X6rJYSESBVr3hBoH0WbKE5KvhPU5bloyZ2L4K60/fPQ=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "c1dfcf08411b08f6b8615f7d8971a2bfa81d5e8a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1719145550,
+        "narHash": "sha256-K0i/coxxTEl30tgt4oALaylQfxqbotTSNb1/+g+mKMQ=",
+        "path": "/nix/store/h5hhc58qp2rcv0f3d9di6569pxrpsi1j-source",
+        "rev": "e4509b3a560c87a8d4cb6f9992b8915abf9e36d8",
+        "type": "path"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs",
+        "rust-overlay": "rust-overlay"
+      }
+    },
+    "rust-overlay": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1728786660,
+        "narHash": "sha256-qY+1e0o6oV5ySlErhj/dsWsPLWjrMKzq4QI7a1t9/Ps=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "174a8d9cec9e2c23877a7b887c52b68ef0421d8b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "type": "github"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  description = "A bare minimum Rust flake";
+
+  inputs = {
+    flake-utils.url = "github:numtide/flake-utils";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, flake-utils, rust-overlay }:
+    flake-utils.lib.eachDefaultSystem (sys:
+      let pkgs = import nixpkgs {
+            system = sys;
+            overlays = [ (import rust-overlay) ];
+          };
+          rust = pkgs.rust-bin.stable.latest.default.override {
+            extensions = [ "rust-src" "rust-analyzer" ];
+          };
+          platform = pkgs.makeRustPlatform {
+            rustc = rust;
+            cargo = rust;
+          };
+      in rec {
+        packages.default = platform.buildRustPackage {
+          name = "my-cool-project";
+          src = ./.;
+          cargoLock = { lockFile = ./Cargo.lock; };
+        };
+        devShells.default = pkgs.mkShell {
+          packages = [ rust ];
+        };
+      }
+    );
+}

src/main.rs

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+use std::io;
+
+fn sqrtu64(x: u64) -> u64 {
+    f64::sqrt(x as f64) as u64 + 1
+}
+
+fn main() {
+    let mut input_line = String::new();
+    io::stdin()
+        .read_line(&mut input_line)
+        .expect("Failed to read line");
+
+    let x: u64 = input_line.trim().parse().expect("Input not an integer");
+    let sqrtx = sqrtu64(x);
+    let mut primes = vec![2,3,5,7];
+    let mut i: u64 = 12;
+
+    while i <= sqrtx {
+        let n = i-1;
+        let m = i+1;
+        let sqrtm = sqrtu64(m);
+
+        let mut nprime = true;
+        let mut mprime = true;
+
+        for prime in &primes {
+            if *prime > sqrtm { break; }
+            if n % prime == 0 {
+                nprime = false;
+                break;
+            }
+            if m % prime == 0 {
+                mprime = false;
+                break;
+            }
+        }
+
+        if nprime { primes.push(n) }
+        if mprime { primes.push(m) }
+
+        i+=6;
+    }
+
+    let mut divisors: Vec<u64> = vec![];
+
+    for div in primes {
+        if x % div == 0 {
+            divisors.push(div);
+        }
+    }
+
+    if divisors.len() == 0 {
+        println!("{} is prime!", x);
+    } else {
+        println!("{} has divisors {:?}", x, divisors);
+    }
+}