Synth¶

Description¶

This contract is the basis of all Synth flavours. It exposes sufficient functionality for the Synthetix and FeePool contracts to manage its supply. Otherwise Synths are fairly vanilla ERC20 tokens; the PurgeableSynth contract extends this basic functionality to allow the owner to liquidate a Synth if its total value is low enough.

See the main synth notes for more information about how Synths function in practice.

A Historical Note on Conversion Fees

Since transfer conversion is not operating, the following is recorded only to be kept in mind in case it is ever reactivated. At present there is no way for users to set a preferred currency.

The Synthetix system has implements both exchange and transfer fees on Synths. Although they should be distinct, the preferred currency auto conversion on transfer only charges the transfer fee, and not the exchange fee. As a result, it is possible to convert Synths more cheaply whenever the transfer fee is less than the conversion fee.

Given that the transfer fee is currently nil, if a user was able to set a preferred currency for themselves, it would be possible by this means to perform free Synth conversions. This would undercut fee revenue for the system to incentivise participants with. If markets had priced in the conversion fee, but were unaware of the exploit, then there would be a profit cycle available for someone exploiting this.

In particular:

Let $\phi_\kappa, \ \phi_\tau \in [0,1]$ be the conversion and transfer fee rates, respectively. Let $\pi_A, \ \pi_B$ be the prices of synths $A$ and $B$ in terms of some implicit common currency. $Q_A$ will be the starting quantity of synth $A$ .

Then to convert from $A$ to $B$ , quantities

$Q^\kappa_B = Q_A\frac{\pi_A}{\pi_B}(1 - \phi_\kappa) \\ Q^\tau_B = Q_A\frac{\pi_A}{\pi_B}(1 - \phi_\tau)$

are received if the user performs a standard conversion or a transfer conversion, respectively. The profit of performing a transfer conversion relative to a standard one is then:

$Q^\tau_B - Q^\kappa_B = Q_A\frac{\pi_A}{\pi_B}(\phi_\kappa - \phi_\tau)$

That is, the relative profit is simply $(\phi_\kappa - \phi_\tau)$ . With no transfer fee, this is $\phi_\kappa$ , as expected.

Synth¶

Description¶

Variables¶

CONTRACT_NAME¶

DECIMALS¶

FEE_ADDRESS¶

currencyKey¶

Constructor¶

constructor¶

Views¶

resolverAddressesRequired¶

transferableSynths¶

Restricted Functions¶

burn¶

issue¶

setTotalSupply¶

transfer¶

transferAndSettle¶

transferFrom¶

transferFromAndSettle¶

Internal Functions¶

_ensureCanTransfer¶

_internalBurn¶

_internalIssue¶

_internalTransferFrom¶

_isInternalContract¶

_isInternalTransferCaller¶

_onlyProxyOrInternal¶

_transferToFeeAddress¶

emitBurned¶

emitIssued¶

exchanger¶

feePool¶

futuresMarketManager¶

issuer¶

systemStatus¶

Modifiers¶

onlyInternalContracts¶

onlyProxyOrInternal¶

Events¶

Burned¶

Issued¶

`CONTRACT_NAME`¶

`DECIMALS`¶

`FEE_ADDRESS`¶

`currencyKey`¶

`constructor`¶

`resolverAddressesRequired`¶

`transferableSynths`¶

`burn`¶

`issue`¶

`setTotalSupply`¶

`transfer`¶

`transferAndSettle`¶

`transferFrom`¶

`transferFromAndSettle`¶

`_ensureCanTransfer`¶

`_internalBurn`¶

`_internalIssue`¶

`_internalTransferFrom`¶

`_isInternalContract`¶

`_isInternalTransferCaller`¶

`_onlyProxyOrInternal`¶

`_transferToFeeAddress`¶

`emitBurned`¶

`emitIssued`¶

`exchanger`¶

`feePool`¶

`futuresMarketManager`¶

`issuer`¶

`systemStatus`¶

`onlyInternalContracts`¶

`onlyProxyOrInternal`¶

`Burned`¶

`Issued`¶