docstring for quick_cancel [ci skip]

Author: shashi

src/polyform.jl

@@ -304,6 +304,15 @@ _gcd(x::MaybeGcd, y::MaybeGcd) = (coefftype(x) <: Complex || coefftype(y) <: Com
 _gcd(x, y) = 1
 
 
+"""
+    quick_cancel(d::Div)
+
+Cancel out matching factors from numerator and denominator.
+This is not as effective as `simplify_fractions`, for example,
+it wouldn't simplify `(x^2 + 15 -  8x)  / (x - 5)` to `(x - 3)`.
+But it will simplify `(x - 5)^2*(x - 3) / (x - 5)` to `(x - 5)*(x - 3)`.
+Has optimized processes for `Mul` and `Pow` terms.
+"""
 quick_cancel(d::Div) = Div{symtype(d)}(quick_cancel(d.num, d.den)...)
 
 quick_cancel(x) = x