contract syntax

## state on the class itself

```ts
import { BigNumber } from "jsd-std";

export class Counter {
private count: BigNumber;

constructor(initialState: BigNumber) {
this.count = initialState;
}

public increment(amount: BigNumber): void {
this.count = this.count.add(amount);
}

public decrement(amount: BigNumber): void {
if (this.count.lt(amount)) {
throw new Error("Count cannot be negative");
}
this.count = this.count.sub(amount);
}

public getCount(): BigNumber {
return this.count;
}
}
```