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Question
· Aug 26, 2022

Is there something like java.math.BigInteger in ObjectScript?

#ObjectScript #InterSystems IRIS

Is it possible to use integer with a higher precision so that something like this works:

ClassMethod BigNumbers()
{
    Set bigInt1 = 9223372036854775807
    Set bigInt2 = 9223372036854775808
    W !,bigInt1
    W !,bigInt2

    Set bigInt3 = 9223372036854775807123456789
    W !,(bigInt3 # 2)
}
9223372036854775807
9223372036854775810   // should be 9223372036854775808
0                     // should be 1

The docs say "... However, with extremely large numbers (larger than 9223372036854775807E127) it is not always possible to convert a numeric string to a Decimal value. ..."[0], but operations on numbers bigger than 9223372036854775807 are not working correctly.

[0] https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls?KEY=GCOS_types#GCOS_types_nonnumasnum_big

Discussion (3)3
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Yaron Munz · Aug 26, 2022

As you probably know the Intersystems IRIS is capable of doing calculations on a numbers in length of up to 19 positions. This is due to the fact that it is stored as a signed 64–bit integer.

If you are using one of the latest version of IRIS which has an "embedded Python" then you will have the Python support for "bignum" or "long".
So you may have a ClassMethod like this:

ClassMethod BigNumbers1() [ Language = python ]
{
a = 9223372036854775807
b = 9223372036854775808
c = 9223372036854775807123456789
print(a)
print(b)
print(c)
print(c%2)
}
 

Which will give you the output:

9223372036854775807
9223372036854775808
9223372036854775807123456789
1
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Steven Hobbs · Aug 26, 2022

A canonical numeric string in ObjectScript can have a very large number of digits.  Such a string can be sorted with ObjectScript sorts-after operator, ]], and reasonably long canonical numeric strings can be used as subscripts and such numeric subscripts are arranged in numerical order before all the subscript strings that do not have the canonical numeric format.

However, when ObjectScript does other kinds arithmetic on a numeric string then that string is converted to an internal format, which has a restricted range and a restricted precision.  ObjectScript currently supports two internal formats.  The default format is a decimal floating-point representation with a precision of approximately 18.96 decimal digits and a maximum number about 9.2E145.  For customers doing scientific calculations or needing a larger range, ObjectScript also supports the IEEE double-precision binary floating-point representation with a precision around 16 decimal digits and a maximum number about 1.7E308.  You get the IEEE floating-point representation with its reduced precision but its greater range by using the $double(x) function or doing arithmetic on a string which would convert to a numeric value beyond the range of the ObjectScript decimal floating-point representation.  When doing arithmetic that combines ObjectScript decimal floating-point values with IEEE binary floating-point values then the decimal floating-point values will be converted to IEEE binary floating point before performing the arithmetic operation.

Here are more picky details.

The ObjectScript decimal floating-point representation has a 64-bit signed significand with a value between -9223372036854775808 and +9223372036854775807 combined with a decimal exponent multiplier between 10**-128 and 10**127.  I.e., a 64-bit twos-complement integer significand and a signed byte as the decimal exponent.  This decimal floating-point representation can exactly represent decimal fractions like 0.1 or 0.005.

The IEEE binary floating-point representation has a sign-bit, an 11-bit exponent exponent encoding, and a 52 bit significand encoding. The significand usually encodes a 53-bit range values between 1.0 and 2.0 - 2**-52 and the exponent usually encodes a power-of-two multiplier between 2**1023 and 2**-1022.  However, certain other encodings will handle +0, -0, +infinity, -infinity and a large number of NaNs (Not-a-Number symbols.)  There are also some encodings with less than 53 bits of precision for very small values in the underflow range of values.  IEEE 64-bit binary floating-point cannot exactly represent most decimal fractions.  The numbers $double(0.1) and $double(0.005) are approximated by values near 0.10000000000000000556 and 0.0050000000000000001041.

I have written some ObjectScript code that can do add, subtract and modulo on long canonical numeric strings for use in a banking application.  However, if you are doing some serious computations on large precision values then you should use the call-in/call-out capabilities of IRIS to access external code in a language other than ObjectScript. Python might be a good choice.  You could use canonical numeric strings as your call-in/call-out representation or you could invent a new encoding using binary string values that could be stored/fetched from an IRIS data base.

ObjectScript was designed to do efficient movements and rearrangements of data stored in data bases.  If you are doing some serious computations between your data base operations then using a programming language other than ObjectScript will probably provide better capabilities for solving your problem.

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