Cosmos-sdk: Reconcile DecCoin/s with Coin/s

[alexanderbez]

Summary

Reconcile the DecCoin and DecCoins APIs with the Coin and Coins APIs for consistency.

e.g.

• Not allowing negative amounts
• Not returning zero amounts in plus
• Consistent constructors and naming conventions
• Improve godocs & test coverage
• etc...

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[rigelrozanski]

What did you have in mind? like testing through an interface? golang is kinda inhibiting for actually combining these two types unfortunately

[alexanderbez]

Yeah I wish we could keep it DRY as possible, but I mean just making sure the APIs are the same (e.g. plus doesn't make sure zero coins are removed).

[alessio]

How about defining these common interfaces?

type Coin interface {
    SameDenomAs(Coin) bool
    Zero() bool
    GTE(Coin) bool
    LT(Coin) bool
    Equal(Coin) bool
    Plus(Coin) Coin
    Minus(Coin) Coin
    Positive() bool
    Negative() bool
    String() string
}

type CoinSet interface {
    Valid() bool
    Plus(CoinSet) Coin
    Minus(CoinSet) Coin
    SafeMinus(CoinSet) Coin
    AllGT(CoinSet) bool
    AllGTE(CoinSet) bool
    AllLTE(CoinSet) bool
    Zero() bool
    Equal(CoinSet) bool
    Empty() bool
    AllPositive() bool
    AllNotNegative() bool
        AnyNegative() bool
    Sort() CoinSet
    String() string
}

Note that I have removed the Is prefix from all types - IMHO it does not add any value to the methods names.

[alessio]

We might need an Amount interface to allow Int/Dec comparisons