https://github.com/oldk1331/fricas/commit/1e58b16c42867b8218439bf1fbbfc6976fe6fb40.patch
The original implementation is unnecessarily complicated.
diff --git a/src/algebra/fr.spad b/src/algebra/fr.spad
index 8d6547cb..8486cf2b 100644
--- a/src/algebra/fr.spad
+++ b/src/algebra/fr.spad
@@ -413,37 +413,20 @@
(expand((u exquo u1)::%) + expand((v exquo u1)::%)) * u1
gcd(u, v) ==
- (u = 1) or (v = 1) => 1
- zero? u => v
- zero? v => u
- f1 := empty()$List(Integer) -- list of used factor indices in x
- f2 := f1 -- list of indices corresponding to a given factor
- f3 := empty()$List(List Integer) -- list of f2-like lists
- x := concat(factorList u, factorList v)
- for i in minIndex x .. maxIndex x repeat
- if not member?(i, f1) then
- f1 := concat(i, f1)
- f2 := [i]
- for j in i+1..maxIndex x repeat
- if x.i.factor = x.j.factor then
- f1 := concat(j, f1)
- f2 := concat(j, f2)
- f3 := concat(f2, f3)
- x1 := empty()$List(FF)
- while not empty? f3 repeat
- f1 := first f3
- if #f1 > 1 then
- i := first f1
- y := copy x.i
- f1 := rest f1
- while not empty? f1 repeat
- i := first f1
- if x.i.exponent < y.exponent then y.exponent := x.i.exponent
- f1 := rest f1
- x1 := concat(y, x1)
- f3 := rest f3
- if comparableR? then x1 := sort!(LispLessP, x1)
- mkFF(1, x1)
+ one? u or one? v => u
+ zero? u => v
+ zero? v => u
+ lu := factorList u; lv := factorList v
+ res : List FF := []
+ while not empty? lu and not empty? lv repeat
+ u1 := first lu; v1 := first lv
+ u1.factor = v1.factor =>
+ res := concat([stricterFlag(u1.flag, v1.flag), u1.factor, _
+ min(u1.exponent, v1.exponent)], res)
+ lu := rest lu; lv := rest lv
+ LispLessP(u1, v1) => lu := rest lu
+ lv := rest lv
+ mkFF(1, reverse! res)
else -- R not a GCD domain
u + v ==
--
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