This section will describe number formats used in our API and also tell you why these
decisions were made.

Monetary Values

Being a financial institution, we put great store by calculating correctly. The default implementation for floating pointer numbers are not suitable for these kinds of calculations.

The two most important problems with floating point numbers are arithmetically imprecise operation and data munging.

Solution

To avoid the aforementioned issues at lemon.markets, we specify monetary values as fixed-point fractions numbers with 4 decimal places after the decimal point. These numbers are wrapped in Strings to provide a precise expression going forward, e.g. "123.4567".

Programming languages with a decimal number type can correctly represent these numbers in memory (in contrast to floating-point numbers). Please refer to these data types if possible:

Java: BigDecimal
Python: decimal
Swift: Decimal

Precision

The lemon.markets platform uses different levels of precision in different contexts of usage.

Monetary Amounts

Monetary amounts are specified by using either two or four decimal places:

2 decimal places are used for transaction values, e.g. a deposit, paying taxes, buying/selling securities. (Whenever you think of something as changing the balance of your account, we’ll use two decimal places.)
4 decimal places are traditionally used for share prices of individual instruments.

Share Quantities

Quantities of shares can be expressed with up to 5 decimal places.

Example

Looking at this trade as an example, we can see all types precisions being used:

Monetary Amount (2 decimal places)
- amount
- fee
Monetary Amount (4 decimal places)
- price
Share Quantity (5 decimal places)
- quantity

{
  "amount": "100.00",
  "currency": "EUR",
  "execution_venue": "XGAT",
  "fee": "0.10",
  "id": "tr_611041a7e62c4e7d82a8dd86f91e7277",
  "instrument": "IE00B0M62X26",
  "order": "bord_b088cafa88564670a4b7e1acc7e30b5b",
  "price": "216.0199",
  "quantity": "0.46292",
  "side": "buy",
  "taxes": []
}

Number Formats