Abelian sandpile model/Identity: Difference between revisions

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@@ Line 3,486: / Line 3,486: @@
 s3_id + s3_id == s3_id: true
 </pre>
+=={{header|Vlang}}==
+{{trans|Go}}
+<lang vlang>import strings
+struct Sandpile {
+mut:
+    a [9]int
+}
+const (
+neighbors = [
+    [1, 3], [0, 2, 4], [1, 5], [0, 4, 6], [1, 3, 5, 7], [2, 4, 8], [3, 7], [4, 6, 8], [5, 7]
+]
+)
+// 'a' is in row order
+fn new_sandpile(a [9]int) Sandpile { return Sandpile{a} }
+fn (s &Sandpile) plus(other &Sandpile) Sandpile {
+    mut b := [9]int{}
+    for i in 0..9 {
+        b[i] = s.a[i] + other.a[i]
+    }
+    return Sandpile{b}
+}
+fn (s &Sandpile) is_stable() bool {
+    for e in s.a {
+        if e > 3 {
+            return false
+        }
+    }
+    return true
+}
+// just topples once so we can observe intermediate results
+fn (mut s Sandpile) topple() {
+    for i in 0..9 {
+        if s.a[i] > 3 {
+            s.a[i] -= 4
+            for j in neighbors[i] {
+                s.a[j]++
+            }
+            return
+        }
+    }
+}
+fn (s Sandpile) str() string {
+    mut sb := strings.new_builder(64)
+    for i in 0..3 {
+        for j in 0..3 {
+            sb.write_string("${u8(s.a[3*i+j])} ")
+        }
+        sb.write_string("\n")
+    }
+    return sb.str()
+}
+fn main() {
+    println("Avalanche of topplings:\n")
+    mut s4 := new_sandpile([4, 3, 3, 3, 1, 2, 0, 2, 3]!)
+    println(s4)
+    for !s4.is_stable() {
+        s4.topple()
+        println(s4)
+    }
+    println("Commutative additions:\n")
+    s1 := new_sandpile([1, 2, 0, 2, 1, 1, 0, 1, 3]!)
+    s2 := new_sandpile([2, 1, 3, 1, 0, 1, 0, 1, 0]!)
+    mut s3_a := s1.plus(s2)
+    for !s3_a.is_stable() {
+        s3_a.topple()
+    }
+    mut s3_b := s2.plus(s1)
+    for !s3_b.is_stable() {
+        s3_b.topple()
+    }
+    println("$s1\nplus\n\n$s2\nequals\n\n$s3_a")
+    println("and\n\n$s2\nplus\n\n$s1\nalso equals\n\n$s3_b")
+    println("Addition of identity sandpile:\n")
+    s3 := new_sandpile([3, 3, 3, 3, 3, 3, 3, 3, 3]!)
+    s3_id := new_sandpile([2, 1, 2, 1, 0, 1, 2, 1, 2]!)
+    s4 = s3.plus(s3_id)
+    for !s4.is_stable() {
+        s4.topple()
+    }
+    println("$s3\nplus\n\n$s3_id\nequals\n\n$s4")
+    println("Addition of identities:\n")
+    mut s5 := s3_id.plus(s3_id)
+    for !s5.is_stable() {
+        s5.topple()
+    }
+    print("$s3_id\nplus\n\n$s3_id\nequals\n\n$s5")
+}</lang>
+{{out}}
+<pre>
+Same as Go entry
+</pre>
 =={{header|Wren}}==
 {{libheader|Wren-fmt}}