Introduction to decimal128
ver 0.1.2
This library creates a data type called Decimal128 that allows one to
store and manipulate decimal numbers.
By storing a number as decimal digits you can avoid the ambiguity and rounding errors encountered when converting values back-and-forth from binary floating point numbers (base 2) and the decimal notation typically used by humans (base 10).
This is especially useful for applications that are not tolerant of such rounding errors such as accounting, banking, and finance.
STANDARD USED
The specification specifically conforms to the IEEE 754-2008 standard that is formally available at https://standards.ieee.org/standard/754-2008.html
A more informal copy of that spec can be seen at http://speleotrove.com/decimal/decbits.html , though that spec only shows the Densely Packed Binary (DPD) version of storing the coefficient. This library supports both DPD and the unsigned binary integer storage (BID) method when for serializing and unserializing from binary images.
The BID method is used by BSON and MongoDB.
EXAMPLES OF USE
import decimal128
let a = newDecimal128("4003.250")
assert a.getPrecision == 7
assert a.getScale == 3
assert a.toFloat == 4003.25
assert a.toInt == 4003
assert $a == "4003.250"
assert a === newDecimal128("4003250E-3")
assert a === newDecimal128("4.003250E+3")
# interpret a segment of data from a BSON file:
let b = decodeDecimal128("2FF83CD7450BE3F39FA2D32880000000", encoding=ceBID)
assert $b == "0.001234000000000000000000000000000000"
assert b.getPrecision == 34
assert b.getScale == 36
assert b.toFloat == 0.001234
assert $(newDecimal128("423.77") + newDecimal128("20.9362")) == "444.71"Table Of Contents
Appendices