任意精度JavaScript上的浮点数

Question

I have some inputs on my site representing floating point numbers with up to ten precision digits (in decimal). At some point, in the client side validation code, I need to compare a couple of those values to see if they are equal or not, and here, as you would expect, the intrinsics of IEEE754 make that simple check fails with things like (2.0000000000==2.0000000001) = true.

I may break the floating point number in two longs for each side of the dot, make each side a 64 bit long and do my comparisons manually, but it looks so ugly!

Any decent Javascript library to handle arbitrary (or at least guaranteed) precision float numbers on Javascript?

Thanks in advance!

PS: A GWT based solution has a ++

Answer 1

There is the GWT-MATH library at http://code.google.com/p/gwt-math/ .

However, I warn you, it's a GWT jsni overlay of a java->javascript automated conversion of java.BigDecimal (actually the old com.ibm.math.BigDecimal).

It works, but speedy it is not. (Nor lean. It will pad on a good 70k into your project).

At my workplace, we are working on a fixed point simple decimal, but nothing worth releasing yet. :(

Answer 2

Use an arbitrary precision integer library such as silentmatt's javascript-biginteger , which can store and calculate with integers of any arbitrary size.

Since you want ten decimal places, you'll need to store the value n as n×10^10 . For example, store 1 as 10000000000 (ten zeroes), 1.5 as 15000000000 (nine zeroes), etc. To display the value to the user, simply place a decimal point in front of the tenth-last character (and then cut off any trailing zeroes if you want).

Alternatively you could store a numerator and a denominator as bigintegers, which would then allow you arbitrarily precise fractional values (but beware – fractional values tend to get very big very quickly).