Move shared code to library

1 files changed, 37 insertions, 0 deletions

diff --git a/pbt/ts/src/property.ts b/pbt/ts/src/property.ts
index a8c59ba..d4eea28 100644
--- a/pbt/ts/src/property.ts
+++ b/pbt/ts/src/property.ts
@@ -64,3 +64,40 @@ export function property<A>(
             return { result: 'OK', tests: i, counterexample: null };
           };
 }
+
+// basic generators
+
+export function listOf<A>(gen: Gen<A>): Gen<A[]> {
+  return (rng: Prando) => {
+    let g = gen(rng);
+    return (size: number) => {
+      let result = [];
+      for (let i = 0; i < size; i++) {
+        result.push(g(size));
+      }
+      return result;
+    };
+  };
+}
+
+export function shrinklist<A>(arr: A[]): A[][] {
+  let result = [];
+
+  let tail = arr.slice(1);
+  let keep1 = arr.slice();
+  keep1.splice(1, 1);
+  result.push(tail,keep1);
+
+  if (arr.length >3) {
+    let half = Math.floor(arr.length / 2);
+    let copy = arr.slice();
+    let secondHalf = copy.slice(half);
+    result.push(secondHalf);
+  }
+
+  return result;
+}
+
+export let someInt : Gen<number> = (rng: Prando) =>
+  (size: number) =>
+    rng.nextInt(-size, size);