(barring typos or other mistakes), as they are in the standard, and Specification (the structure of the number, the context, etc.).Īll the requirements included in this section are not for discussion Here I’ll include information and descriptions that are part of the Total world economic output, down to the penny, since theīeginning of time. Need to calculate the common denominator).Ī precision of 20 would be way more than enough to account for This implies that the arithmetic operationsĬan’t be executed directly (e.g. Rational numbers are stored using two integer numbers, the numeratorĪnd the denominator. With this exposed maybe you’re thinking “Hey! Can we just store the 1Īnd the 3 as numerator and denominator?”, which takes us to the next ![]() Wants to have support for the / operator in a numeric data type. This generated adverse reactions in, as everybody User to use an explicit method, just to avoid this kind of trouble. John Roth proposed to eliminate the division operator and force the Infinite amount of 3s, which takes too much memory, ). It’s not so easy, because of inexact divisions. Implement a fixed point data type over Decimal.īut why can’t we have a floating point number with infinite precision? Implement the arithmetic behaviour of the standard, and then you can I’ll go for floating point because it’s easier to In a fixed point number, the position of the decimal point is fixed.įor a fixed point data type, check Tim Peter’s FixedPoint at Precision, meaning that you can have the number as big as you want, In contrast, we have the example of a long integer with infinite (note that in the last line the number got rounded to fit in five digits). Represent a number, working with an exponent when the number gets tooīig or too small. So we go to decimal, but why floating point?įloating point numbers use a fixed quantity of digits (precision) to Instead of a binary data type, we need a decimal one. So we need a decimal data type that represents exactly decimal Numbers can’t be represented exactly in binary, resulting in small Decimal 0.2 equals 2/10 equalsġ/5, resulting in the binary fractional numberĠ.001100110011001… As you can see, the problem is that some decimal In decimal math, there are many numbers that can’t be represented withĪ fixed number of decimal digits, e.g. Will also provide unrounded decimal arithmetic and integer arithmeticĪs proper subsets. Specification will conform to the decimal arithmetic defined inĪNSI/IEEE standard 854-1987, except for some minor restrictions, and Standard GvR redirected me: Mike Cowlishaw’s General DecimalĪrithmetic specification. Someone already thought out all the creepy cases for you. One of the biggest advantages of implementing a standard is that Purpose of this PEP to have a data type that can be used as Money Point, rounding, etc., will be handled through Money. With the needed arithmetic behaviour, and then build Money over it:Īll the considerations about quantity of digits after the decimal I wanted a Money data type, and after proposing a pre-PEP inĬ, the community agreed to have a numeric data type ![]() Needed and why other numeric data types are not enough. Here I’ll expose the reasons of why I think a Decimal data type is Much of the explanation in this PEP is taken fromĬowlishaw’s work, and python-dev. With the documentation and the test suite, this was the work of Reference implementation was moved into the standard library along This work is based on code and test functions written by Eric Price,Īahz and Tim Peters. So that fixed-point usage is also possible. User-settable, and a notion of significant trailing zeroes is supported Number of significant digits in a result). Have bounded precision (the precision is the upper limit on the Operations, and must comply with the decimal arithmetic ANSI standardĭecimal will be floating point (as opposed to fixed point) and will The Decimal data type will support the Python standard functions and The idea is to have a Decimal data type, for every use where decimalsĪre needed but binary floating point is too inexact. General Decimal Arithmetic Specification.Toggle light / dark / auto colour theme PEP 327 – Decimal Data Type Author : Facundo Batista Status : Final Type : Standards Track Created : 1 Python-Version : 2.4 Post-History : 3, 0, 2 PEP 327 – Decimal Data Type | Following system colour scheme Selected dark colour scheme Selected light colour scheme Python Enhancement Proposals
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