[rust-dev] Appeal for CORRECT, capable, future-proof math, pre-1.0

Isaac Dupree ml at isaac.cedarswampstudios.org
Fri Jan 10 21:58:59 PST 2014

Scheme's numeric tower is one of the best in extant languages.  Take a 
look at it.  Of course, its dynamic typing is poorly suited for Rust.

Arbitrary-precision arithmetic can get you mathematically perfect 
integers and rational numbers, but not real numbers.  There are an 
uncountably infinite number of real numbers and sophisticated computer 
algebra systems are devoted the problem (or estimates are used, or you 
become unable to compare two real numbers for equality).  The MPFR C 
library implements arbitrarily high precision floating point, but that 
still has all the pitfalls of floating-point that you complain about. 
For starters, try representing sqrt(2) and testing its equality with 
e^(0.5 ln 2).

In general, Rust is a systems language, so fixed-size integral types are 
important to have.  They are better-behaved than in C and C++ in that 
signed types are modulo, not undefined behaviour, on overflow.  It could 
be nice to have integral types that are task-failure on overflow as an 
option too.  As you note, bignum integers are important too; it's good 
they're available.  I think bignum rationals would be a fine additional 
choice to have (Haskell and GMP offer them, for example).


On 01/11/2014 12:15 AM, Lee Braiden wrote:
> This may be go nowhere, especially so late in Rust's development, but I
> feel like this is an important, relatively small change (though a
> high-profile one).  I believe it could have a large, positive impact in
> terms of targeting new developer communities, gaining more libraries and
> applications, giving a better impression of the language, AND on
> performance and futureproofing.
> However, a lot of people who are interested in performance will probably
> baulk at this, on first sight.  If you're in that group, let me
> encourage you to keep reading, at least until the points on performance
> /improvements/.  Then baulk, if you like ;)
> Also, I said it in the post as well, but it's late here, so apologies
> for any readability / editing issues.  I tried, but sleep beckons ;)
> http://blog.irukado.org/2014/01/an-appeal-for-correct-capable-future-proof-math-in-nascent-programming-languages/
> --
> Lee
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