This patch move the implementation of "first(x, n)" from
STAGG to URAGG; also add a specialized version for List.
--
You received this message because you are subscribed to the Google Groups
"FriCAS - computer algebra system" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to fricas-devel+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/fricas-devel/CAGBJN91HYc0MXxQofoOx9xyqMx-hNTC4b-n2G0hySzRZr1e1qA%40mail.gmail.com.
diff --git a/src/algebra/aggcat.spad b/src/algebra/aggcat.spad
index 2a057cb8..01ffaaba 100644
--- a/src/algebra/aggcat.spad
+++ b/src/algebra/aggcat.spad
@@ -1420,6 +1420,18 @@ UnaryRecursiveAggregate(S : Type) : Category == RecursiveAggregate S with
cyclic? x == not empty? x and not empty? findCycle x
last x == first tail x
+ first(x, n) ==
+ l : List S := []
+ for i in 1..n repeat
+ empty? x => error "Index out of range"
+ l := concat(first x, l)
+ x := rest x
+ res : % := empty()
+ while not empty? l repeat
+ res := concat(first l, res)
+ l := rest l
+ res
+
nodes x ==
l := empty()$List(%)
while not empty? x repeat
@@ -1616,15 +1628,8 @@ StreamAggregate(S : Type) : Category ==
import from Integer
- c2 : (%, %) -> S
-
explicitlyFinite? x == not cyclic? x
possiblyInfinite? x == cyclic? x
- first(x, n) == construct [c2(x, x := rest x) for i in 1..n]
-
- c2(x, r) ==
- empty? x => error "Index out of range"
- first x
elt(x : %, i : Integer) ==
i := i - minIndex x
diff --git a/src/algebra/list.spad b/src/algebra/list.spad
index 7f382a03..e3d19e51 100644
--- a/src/algebra/list.spad
+++ b/src/algebra/list.spad
@@ -100,6 +100,14 @@ List(S : Type) : Exports == Implementation where
minIndex x == LISTMININDEX
maxIndex x == # x
+ first(x, n) ==
+ l : % := empty()
+ for i in 1..n repeat
+ empty? x => error "Index out of range"
+ l := concat(first x, l)
+ x := rest x
+ reverse! l
+
rest(x, n) ==
for i in 1..n repeat
if empty? x then error "index out of range"
