Usage examples? about javascript-bignum HOT 6 CLOSED

Wait, I see a a few examples if I scroll down.

So if I understand properly, the following would sum 5 and 8 together: fn["+"](5, 8).

So to do (5+8)*(3-6) it would be:

fn["*"]( fn["+"](5, 8), fn["-"](3, 6) )

And if I want to do 10%3, that would be: fn.mod(10, 3) which would result in 1.
(I noticed there is no fn["%"](a, b) version of mod, which would be nice.)

Do I have the syntax right?

from javascript-bignum.

One more question, so to use big numbers, do I need to wrap them in quotes, or just use them literally?

e.g., fn["*"](8833943883332344019357498834, 109873475987293847960119823745795555.234) Does that work?

I'll get to try it soon.

from javascript-bignum.

By the way, putting some nice usage examples here on the github page might attract more users.

from javascript-bignum.

@trusktr

Thanks for the suggestions. For more complete examples, please see the examples directory, specifically this exact arithmetic example and this complex numbers example. Both examples build a small abstraction layer around javascript-bignum to facilitate switching to native arithmetic or another library. The Moebius example also replaces the clunky function names like fn["+"] with names inspired by C like "cadd".

You have to quote the numbers, or else you lose exactness and end up with normal JavaScript arithmetic. For example, alert(8833943883332344019357498834) gives "8.833943883332344e+27". The extra precision is lost as soon as soon as the browser parses the number, before the library can see it. Scheme can mix exact and inexact numbers, but the result is usually inexact. We have fn["exact?"] to know for sure.

from javascript-bignum.

Cool. Thanks for that great info and links.

By "inexact", do you mean for example that 3.141592653589793238462643383279502884197169399375105820974944592307816406286 (pi) would be considered inexact? So if you add 1/3 and 1/3 you'd get 2/3, but if you convert it to decimal form at any level of precision, it'd be inexact? Is that what you mean when you refer to "inexact"?

from javascript-bignum.

It's a little more than that. In Scheme (and javascript-bignum) every number value is tagged either exact or inexact. "3.14159" would be inexact due to the decimal, but "#e3.14159" would be exact, because of the exactness prefix "#e". However, it would not be exactly pi, it would be 314159/100000.

Similarly, "1/3" is exact, but "#i1/3" is inexact. You can even have inexact integers, such as "#i42" or its equivalent "42.0". fn["/"]("1","3") would give you exact 1/3, since both operands are exact, but fn["/"]("1.","3") would give an inexact since "1." is inexact (equivalent to "1.0"). In javascript-bignum (and typically in Scheme) inexact reals are just IEEE doubles, the same as JavaScript numbers.

By "convert it to decimal" I take you to mean conversion to a string using the characters '0' to '9' and possibly '-' '.' or exponential notation. Strings are not numbers, so the exactness property does not apply. If you mean, would the string yield an exact number if passed to the library, that depends on how you converted it. fn["number->string"] preserves exactness, appending "." or using "a/b" form if necessary. The ECMAScript methods (toFixed, etc.) do not.

Please consult the Scheme standard for full details.

from javascript-bignum.