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Document number: N3965

Date: 2014-02-28

Proposal for Unbounded-Precision Integer Types

by Pete Becker

Excerpt:

Programmers sometimes need to manipulate integer values that are too large to repesent with C++’s standard integer types. Doing a Google search for terms that describe large integers produces many hits for libraries that handle large integers. These libraries vary in quality, from hacks by beginners to sophisticated, professional implementations. Also, Java has unbounded precision integers as part of its standard class library.

One important use for unbounded-precision integers is cryptography. Cryptographic applications typically manipulate integer values of several hundred digits. If the C++ standard library provides facilities for such values it will make cryptographic applications easier to write and to port.

There have been two Committee papers proposing unbounded-precision integer libraries for C++: N1718 (2004) and N2143 (2007), both by M.J. Kronenburg. Nothing was done with these papers, in part because there was too much else going on in the Library Working Group at the time. Now that the Committee is looking to greatly expand the scope of the standard library, it’s time to reconsider unbounded-precision integers.