export class OneShot<A> {
   private value: A | undefined = undefined;

   isSet(): boolean {
      return this.value != null;
   }

   set(v: A) {
      if (v == null) throw new Error("Defect: OneShot variable cannot be set to null value");
      if (this.value != null) throw new Error("Defect: OneShot variable cannot be set twice");
      this.value = v;
   }

   get(): A {
      if (this.value == null) throw new Error("Defect: OneShot variable not set");
      return this.value;
   }
}