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Merged
merged 2 commits into from
Nov 14, 2025
Merged

Generic map and reduce #86

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d1889aa
Generic Map/Reduce functions
cesartw Nov 14, 2025
9538e75
fix httputilx test
cesartw Nov 14, 2025
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2 changes: 1 addition & 1 deletion httputilx/httputilx_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -202,7 +202,7 @@ func TestFetch(t *testing.T) {
cases := []struct {
in, want, wantErr string
}{
{"http://example.com", "<html>", ""},
{"http://example.com", "<html", ""},
{"http://fairly-certain-this-doesnt-exist-asdasd12g1ghdfddd.com", "", "cannot download"},
{"http://httpbin.org/status/400", "", "400"},
{"http://httpbin.org/status/500", "", "500"},
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19 changes: 14 additions & 5 deletions sliceutil/sliceutil.go
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Expand Up @@ -162,18 +162,27 @@ func FilterEmpty[T comparable](t T) bool {
}

// Map returns a list where each item in list has been modified by fn
func Map[T comparable](tt []T, fn func(T) T) []T {
ret := make([]T, len(tt))
func Map[InputTyp, OutputTyp any](tt []InputTyp, fn func(InputTyp) OutputTyp) []OutputTyp {
ret := make([]OutputTyp, len(tt))
for i, t := range tt {
ret[i] = fn(t)
}

return ret
}

// InterfaceSliceTo converts []interface to any given slice.
// It will ~optimistically~ try to convert interface item to the dst item type
func InterfaceSliceTo(src []interface{}, dst interface{}) interface{} {
// Reduce returns an aggregation of tt
func Reduce[InputTyp, AccTyp any](tt []InputTyp, fn func(AccTyp, InputTyp) AccTyp, acc AccTyp) AccTyp {
for _, t := range tt {
acc = fn(acc, t)
}

return acc
}

// InterfaceSliceTo converts []any to any given slice.
// It will ~optimistically~ try to convert any item to the dst item type
func InterfaceSliceTo(src []any, dst any) any {
dstt := reflect.TypeOf(dst)
if dstt.Kind() != reflect.Slice {
panic("`dst` is not an slice")
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66 changes: 66 additions & 0 deletions sliceutil/sliceutil_test.go
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Expand Up @@ -576,6 +576,72 @@ func TestMap_String(t *testing.T) {
}
}

func TestMap_Int(t *testing.T) {
cases := []struct {
in []string
want []int
f func(string) int
}{
{
in: []string{"1", "5", "2"},
want: []int{1, 5, 2},
f: func(s string) int {
n, _ := strconv.Atoi(s) // notlint: errcheck
return n
},
},
}
for _, tc := range cases {
t.Run("", func(t *testing.T) {
out := Map(tc.in, tc.f)
if !reflect.DeepEqual(tc.want, out) {
t.Errorf("\nout: %#v\nwant: %#v\n", out, tc.want)
}
})
}
}

func TestReduce_Int(t *testing.T) {
cases := []struct {
in []int
want int64
f func(int64, int) int64
}{
{
in: []int{1, 5, 2},
want: 8,
f: func(acc int64, i int) int64 {
return acc + int64(i)
},
},
}
for _, tc := range cases {
t.Run("", func(t *testing.T) {
out := Reduce(tc.in, tc.f, 0)
if !reflect.DeepEqual(tc.want, out) {
t.Errorf("\nout: %#v\nwant: %#v\n", out, tc.want)
}
})
}
}

func TestReduce_Struct(t *testing.T) {
type Acc struct {
acc int
}

out := Reduce(
[]int{1, 2, 3},
func(out Acc, i int) Acc {
out.acc += i
return out
},
Acc{})
if out.acc != 6 {
t.Errorf("\nout: %#v\nwant: %#v\n", out.acc, 6)
}
}

func TestInterfaceSliceTo(t *testing.T) {
{
src := []interface{}{"1", "2", "3", "4", "5"}
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