slices: use !{{Less}} instead of {{GreaterOrEqual}}

In CL 371574 PatchSet 18, we replaced all !{{Less}} with {{GreaterOrEqual}} to fix a problem(handle NaNs when sorting float64 slice) in exp/slices.

We don't actually need this change, because we don't guarantee that the slice will be sorted eventually if there are NaNs(we could have a[i] < a[j] for some i,j with i>j).

This CL reverts all the replacements in exp/slices and does not affect any codes in the sort package.

Change-Id: Idc225d480de3e2efef2add35c709ed880d1306cb
Reviewed-on: https://go-review.googlesource.com/c/go/+/400534
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Eli Bendersky <eliben@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Keith Randall <khr@google.com>

diff --git a/src/sort/gen_sort_variants.go b/src/sort/gen_sort_variants.go
index 2b671ceb02bbbc5fb959b1222762ef1e5578904a..d738cac9175f11746adba3a464eaa0426bf94093 100644 (file)
--- a/src/sort/gen_sort_variants.go
+++ b/src/sort/gen_sort_variants.go
@@ -84,9 +84,6 @@ func main() {
                        ExtraArg:   "",
                        DataType:   "[]E",
                        Funcs: template.FuncMap{
-                               "GreaterOrEqual": func(name, i, j string) string {
-                                       return fmt.Sprintf("(%s[%s] >= %s[%s])", name, i, name, j)
-                               },
                                "Less": func(name, i, j string) string {
                                        return fmt.Sprintf("(%s[%s] < %s[%s])", name, i, name, j)
                                },
@@ -106,9 +103,6 @@ func main() {
                        ExtraArg:   ", less",
                        DataType:   "[]E",
                        Funcs: template.FuncMap{
-                               "GreaterOrEqual": func(name, i, j string) string {
-                                       return fmt.Sprintf("!less(%s[%s], %s[%s])", name, i, name, j)
-                               },
                                "Less": func(name, i, j string) string {
                                        return fmt.Sprintf("less(%s[%s], %s[%s])", name, i, name, j)
                                },
@@ -129,9 +123,6 @@ func main() {
                        ExtraArg:   "",
                        DataType:   "Interface",
                        Funcs: template.FuncMap{
-                               "GreaterOrEqual": func(name, i, j string) string {
-                                       return fmt.Sprintf("!%s.Less(%s, %s)", name, i, j)
-                               },
                                "Less": func(name, i, j string) string {
                                        return fmt.Sprintf("%s.Less(%s, %s)", name, i, j)
                                },
@@ -152,9 +143,6 @@ func main() {
                        ExtraArg:   "",
                        DataType:   "lessSwap",
                        Funcs: template.FuncMap{
-                               "GreaterOrEqual": func(name, i, j string) string {
-                                       return fmt.Sprintf("!%s.Less(%s, %s)", name, i, j)
-                               },
                                "Less": func(name, i, j string) string {
                                        return fmt.Sprintf("%s.Less(%s, %s)", name, i, j)
                                },
@@ -222,7 +210,7 @@ func siftDown{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, lo, hi, first int
                if child+1 < hi && {{Less "data" "first+child" "first+child+1"}} {
                        child++
                }
-               if {{GreaterOrEqual "data" "first+root" "first+child"}} {
+               if !{{Less "data" "first+root" "first+child"}} {
                        return
                }
                {{Swap "data" "first+root" "first+child"}}
@@ -300,7 +288,7 @@ func pdqsort{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, a, b, limit int {{
 
                // Probably the slice contains many duplicate elements, partition the slice into
                // elements equal to and elements greater than the pivot.
-               if a > 0 && {{GreaterOrEqual "data" "a-1" "pivot"}} {
+               if a > 0 && !{{Less "data" "a-1" "pivot"}} {
                        mid := partitionEqual{{.FuncSuffix}}(data, a, b, pivot {{.ExtraArg}})
                        a = mid
                        continue
@@ -334,7 +322,7 @@ func partition{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, a, b, pivot int
        for i <= j && {{Less "data" "i" "a"}} {
                i++
        }
-       for i <= j && {{GreaterOrEqual "data" "j" "a"}} {
+       for i <= j && !{{Less "data" "j" "a"}} {
                j--
        }
        if i > j {
@@ -349,7 +337,7 @@ func partition{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, a, b, pivot int
                for i <= j && {{Less "data" "i" "a"}} {
                        i++
                }
-               for i <= j && {{GreaterOrEqual "data" "j" "a"}} {
+               for i <= j && !{{Less "data" "j" "a"}} {
                        j--
                }
                if i > j {
@@ -370,7 +358,7 @@ func partitionEqual{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, a, b, pivot
        i, j := a+1, b-1 // i and j are inclusive of the elements remaining to be partitioned
 
        for {
-               for i <= j && {{GreaterOrEqual "data" "a" "i"}} {
+               for i <= j && !{{Less "data" "a" "i"}} {
                        i++
                }
                for i <= j && {{Less "data" "a" "j"}} {
@@ -394,7 +382,7 @@ func partialInsertionSort{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, a, b
        )
        i := a + 1
        for j := 0; j < maxSteps; j++ {
-               for i < b && {{GreaterOrEqual "data" "i" "i-1"}} {
+               for i < b && !{{Less "data" "i" "i-1"}} {
                        i++
                }
 
@@ -411,7 +399,7 @@ func partialInsertionSort{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, a, b
                // Shift the smaller one to the left.
                if i-a >= 2 {
                        for j := i - 1; j >= 1; j-- {
-                               if {{GreaterOrEqual "data" "j" "j-1"}} {
+                               if !{{Less "data" "j" "j-1"}} {
                                        break
                                }
                                {{Swap "data" "j" "j-1"}}
@@ -420,7 +408,7 @@ func partialInsertionSort{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, a, b
                // Shift the greater one to the right.
                if b-i >= 2 {
                        for j := i + 1; j < b; j++ {
-                               if {{GreaterOrEqual "data" "j" "j-1"}} {
+                               if !{{Less "data" "j" "j-1"}} {
                                        break
                                }
                                {{Swap "data" "j" "j-1"}}
@@ -606,7 +594,7 @@ func symMerge{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, a, m, b int {{.Ex
                j := m
                for i < j {
                        h := int(uint(i+j) >> 1)
-                       if {{GreaterOrEqual "data" "m" "h"}} {
+                       if !{{Less "data" "m" "h"}} {
                                i = h + 1
                        } else {
                                j = h
@@ -633,7 +621,7 @@ func symMerge{{.FuncSuffix}}{{.TypeParam}}(data {{.DataType}}, a, m, b int {{.Ex
 
        for start < r {
                c := int(uint(start+r) >> 1)
-               if {{GreaterOrEqual "data" "p-c" "c"}} {
+               if !{{Less "data" "p-c" "c"}} {
                        start = c + 1
                } else {
                        r = c