In-place operation in a reduction context is not reduced.

[mahrud]

Seems like in-place operations are not reducing the result before changing the host object. Example:

var BN=require('bn.js')
red = new BN.red(new BN(13))
a = new BN(2).toRed(red)
b = new BN(7).toRed(red)
x = a.redIMul(b)

red.m // <BN: d>
x // <BN-R: 1>
x.cmp(red.m) // correct
a // <BN-R: e>
a.cmp(red.m) // incorrect

Note that a is still in a reduction context, but its value is larger than the modulus!

[fanatid]

This happens because Red#imod is not actually imod... :(

bn.js/lib/bn.js

Line 3172 in 98ac84e

return a.umod(this.m)._forceRed(this);

[dcousens]

See #178