# `gno.land/p/moul/x/social/coin/v0`
**A GRC20 that refuses to exist until its mint rule, its sink and its buyer are
written down**: `New`, `Earn`, `Spend`, `Supply`, `Earned`, `Spent`, `Render`.
```go
import "gno.land/p/moul/x/social/coin/v0"
var points = coin.New("Thread Points", "THREAD", 0, 0, coin.Policy{
Mint: "1 per distinct address that replies to your thread",
Sink: "burned to pin a thread to the top of its page",
Buyer: "anyone who wants placement and has not earned it",
}, 0, cur)
points.Earn(author, 1) // the mint rule, with exactly one call site
points.Spend(buyer, 10) // the sink, which is the only thing that removes supply
```
The three strings are the whole point. `New` panics on a blank one, so the
declaration happens before the first unit exists rather than in a README written
afterwards, and `Render` prints all three on the issuing realm's own page, where
being wrong about them is visible to the people holding the token.
**A mint rule with no sink is a scoreboard with a price.** Supply only grows, the
number is the product, and a holder has no reason to buy one from an earner.
Nothing in a package can check that a declared sink is real, which is exactly why
it is a declaration and not a validation: the cheap failure is forgetting to
decide, not lying.
`Earned` and `Spent` are kept separately from the supply because a sink that
never fires is invisible in the supply alone. A flat line reads the same as no
sink at all; two counters say which it is.
`Earn` of a non-positive amount is a no-op rather than an abort. A mint rule that
computes zero means nothing new happened, and that should not fail the
transaction that discovered it. `Spend` is the opposite and aborts naming both
numbers, because its caller is a user about to be told they cannot afford
something.
Everything else is the embedded [`p/nt/grc20`](https://gno.land/p/nt/grc20/v0):
transfers, approvals, balances and events are an ordinary GRC20, so wallets and
indexers need to know nothing about this package. `Token()` hands it over for the
realm to expose and to register with a token registry.
The trailing `_ int, rlm realm` on `New` is the shape a pure package has to use
to reach the caller's frame: a `p/` may not declare a crossing function, so the
realm token is threaded as a later parameter, exactly as grc20's own tellers do.
**Live user:** [`r/moul/x/social/threads`](https://github.com/moul/gno-contracts/tree/main/r/moul/x/social/threads).
<!-- BEGIN GNOCONTRACTS FOOTER (generated by `make readmes`; do not edit below) -->
---
Part of **[moul/gno-contracts](https://github.com/moul/gno-contracts)** — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.
**Dependency graph:**
> 🧪 **Highly experimental — potentially vibe-coded.** Not audited; may break, change, or be removed at any time. Do not use with anything of value. Full disclaimer: [DISCLAIMER](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).
<!-- END GNOCONTRACTS FOOTER -->
Signatures reconstructed verbatim from vm/qfuncs — interface params keep their inline definitions.