[go] math/big: add Floor and Ceil methods to Rat
Gerrit Bot (Gerrit)
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Commit message
math/big: add Floor and Ceil methods to Rat
Adds methods for floor and ceil of a rational number r, floor(r) is the
largest integer <= r and ceil(r) is the smallest integer >= r.
Change diff
diff --git a/src/math/big/rat.go b/src/math/big/rat.go
index c7f79a5..1a8e2a6 100644
--- a/src/math/big/rat.go
+++ b/src/math/big/rat.go
@@ -559,3 +559,18 @@
z.a.neg = a.neg != b.neg
return z.norm()
}
+
+// Floor returns the largest [Int] <= z.
+func (z *Rat) Floor() *Int {
+ // z.b is positive, so Euclidean division == floor division
+ return new(Int).Div(&z.a, &z.b)
+}
+
+// Ceil returns the smallest [Int] >= z.
+func (z *Rat) Ceil() *Int {
+ if z.IsInt() {
+ return new(Int).Set(&z.a)
+ }
+ f := z.Floor()
+ return f.Add(f, intOne)
+}
diff --git a/src/math/big/rat_test.go b/src/math/big/rat_test.go
index d98c89b..0431ab9 100644
--- a/src/math/big/rat_test.go
+++ b/src/math/big/rat_test.go
@@ -744,3 +744,53 @@
<-c
}
}
+
+var ratFloorTests = []struct {
+ rat string
+ out int64
+}{
+ {"123456.78", 123456},
+ {"100.5", 100},
+ {"5645.0222", 5645},
+ {"89898989", 89898989},
+ {"0", 0},
+ {"-123456.78", -123457},
+ {"-100.5", -101},
+ {"-5645.0222", -5646},
+ {"-89898989", -89898989},
+}
+
+func TestRatFloor(t *testing.T) {
+ for i, test := range ratFloorTests {
+ x, _ := new(Rat).SetString(test.rat)
+ out := x.Floor()
+ if out.Cmp(NewInt(test.out)) != 0 {
+ t.Errorf("#%d got out = %v; want %v", i, out, test.out)
+ }
+ }
+}
+
+var ratCeilTests = []struct {
+ rat string
+ out int64
+}{
+ {"123456.78", 123457},
+ {"100.5", 101},
+ {"5645.0222", 5646},
+ {"89898989", 89898989},
+ {"0", 0},
+ {"-123456.78", -123456},
+ {"-100.5", -100},
+ {"-5645.0222", -5645},
+ {"-89898989", -89898989},
+}
+
+func TestRatCeil(t *testing.T) {
+ for i, test := range ratCeilTests {
+ x, _ := new(Rat).SetString(test.rat)
+ out := x.Ceil()
+ if out.Cmp(NewInt(test.out)) != 0 {
+ t.Errorf("#%d got out = %v; want %v", i, out, test.out)
+ }
+ }
+}
Change information
- M src/math/big/rat.go
- M src/math/big/rat_test.go
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Gopher Robot (Gerrit)
Gopher Robot added 1 comment![]( "Open in Gerrit")
I spotted some possible problems with your PR:
1. You usually need to reference a bug number for all but trivial or cosmetic fixes. For this repo, the format is usually 'Fixes #12345' or 'Updates #12345' at the end of the commit message. Should you have a bug reference?
Please address any problems by updating the GitHub PR.
When complete, mark this comment as 'Done' and click the [blue 'Reply' button](https://go.dev/wiki/GerritBot#i-left-a-reply-to-a-comment-in-gerrit-but-no-one-but-me-can-see-it) above. These findings are based on heuristics; if a finding does not apply, briefly reply here saying so.
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armin (Gerrit)
armin added 1 comment![]( "Open in Gerrit")
I spotted some possible problems with your PR:
1. You usually need to reference a bug number for all but trivial or cosmetic fixes. For this repo, the format is usually 'Fixes #12345' or 'Updates #12345' at the end of the commit message. Should you have a bug reference?Please address any problems by updating the GitHub PR.
When complete, mark this comment as 'Done' and click the [blue 'Reply' button](https://go.dev/wiki/GerritBot#i-left-a-reply-to-a-comment-in-gerrit-but-no-one-but-me-can-see-it) above. These findings are based on heuristics; if a finding does not apply, briefly reply here saying so.
To update the commit title or commit message body shown here in Gerrit, you must edit the GitHub PR title and PR description (the first comment) in the GitHub web interface using the 'Edit' button or 'Edit' menu entry there. Note: pushing a new commit to the PR will not automatically update the commit message used by Gerrit.
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(In general for Gerrit code reviews, the change author is expected to [log in to Gerrit](https://go-review.googlesource.com/login/) with a Gmail or other Google account and then close out each piece of feedback by marking it as 'Done' if implemented as suggested or otherwise reply to each review comment. See the [Review](https://go.dev/doc/contribute#review) section of the Contributing Guide for details.)
Done
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Alan Donovan (Gerrit)
Alan Donovan added 3 comments![]( "Open in Gerrit")
This looks reasonable; it will need to wait for the proposal to be accepted, and for the go1.26 freeze to end (in Feb) before we merge it though.
// Floor returns the largest [Int] <= z.
func (z *Rat) Floor() *Int {
// z.b is positive, so Euclidean division == floor division
return new(Int).Div(&z.a, &z.b)
}
// Ceil returns the smallest [Int] >= z.
func (z *Rat) Ceil() *Int {(Following Num and Denom, it seems fine not to accept an additional destination *Int variable, which is an allocation optimization.)
var ratFloorTests = []struct {This can be a local variable (or literal) of the test. Ditto Ceil.
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| Hold | +1 |
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Armin Günther (Gerrit)
Armin Günther added 1 comment![]( "Open in Gerrit")
This can be a local variable (or literal) of the test. Ditto Ceil.
Done
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Alan Donovan (Gerrit)
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1 comment
Code LGTM. Could you also add a release note (in GOROOT/doc/next) and an API manifest (in GOROOT/api/next)? The manifest should mention the issue number of the proposal, which is now the blocker.
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Armin Günther (Gerrit)
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Code LGTM. Could you also add a release note (in GOROOT/doc/next) and an API manifest (in GOROOT/api/next)? The manifest should mention the issue number of the proposal, which is now the blocker.
Done. (I think?)
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Armin Günther (Gerrit)
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Updated according to issue.
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