initial commit

math/math.go

@@ -0,0 +1,71 @@
+package math
+
+type signed interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64
+}
+type unsigned interface {
+	~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr
+}
+type integer interface {
+	signed | unsigned
+}
+type float interface {
+	~float32 | ~float64
+}
+type ordered interface {
+	integer | float | ~string
+}
+
+func Abs[T signed](i T) T {
+	if i > 0 {
+		return i
+	}
+	return -i
+}
+func Max[T ordered](i T, candidates ...T) T {
+	for _, j := range candidates {
+		if i < j {
+			i = j
+		}
+	}
+	return i
+}
+func Min[T ordered](i T, candidates ...T) T {
+	for _, j := range candidates {
+		if i > j {
+			i = j
+		}
+	}
+	return i
+}
+
+func PagerBox(first, last uint64, pos, count int64) (uint64, int64) {
+	var start uint64
+
+	if pos >= 0 {
+		if int64(first) > pos {
+			start = first
+		} else {
+			start = uint64(pos) + 1
+		}
+	} else {
+		start = uint64(int64(last) + pos + 1)
+	}
+
+	switch {
+	case count > 0:
+		count = Min(count, int64(last-start)+1)
+
+	case pos >= 0 && count < 0:
+		count = Max(count, int64(first-start))
+
+	case pos < 0 && count < 0:
+		count = Max(count, int64(first-start)-1)
+	}
+
+	if count == 0 || (start < first && count <= 0) || (start > last && count >= 0) {
+		return 0, 0
+	}
+
+	return start, count
+}

math/math_test.go

@@ -0,0 +1,96 @@
+package math_test
+
+import (
+	"testing"
+
+	"github.com/matryer/is"
+	"go.sour.is/pkg/math"
+)
+
+func TestMath(t *testing.T) {
+	is := is.New(t)
+
+	is.Equal(5, math.Abs(-5))
+	is.Equal(math.Abs(5), math.Abs(-5))
+
+	is.Equal(10, math.Max(1, 2, 3, 4, 5, 6, 7, 8, 9, 10))
+	is.Equal(1, math.Min(1, 2, 3, 4, 5, 6, 7, 8, 9, 10))
+
+	is.Equal(1, math.Min(89, 71, 54, 48, 49, 1, 72, 88, 25, 69))
+	is.Equal(89, math.Max(89, 71, 54, 48, 49, 1, 72, 88, 25, 69))
+
+	is.Equal(0.9348207729, math.Max(
+		0.3943310720,
+		0.1090868377,
+		0.9348207729,
+		0.3525527584,
+		0.4359833682,
+		0.7958538081,
+		0.1439352569,
+		0.1547311967,
+		0.6403818871,
+		0.8618832818,
+	))
+
+	is.Equal(0.1090868377, math.Min(
+		0.3943310720,
+		0.1090868377,
+		0.9348207729,
+		0.3525527584,
+		0.4359833682,
+		0.7958538081,
+		0.1439352569,
+		0.1547311967,
+		0.6403818871,
+		0.8618832818,
+	))
+
+}
+
+func TestPagerBox(t *testing.T) {
+	is := is.New(t)
+
+	tests := []struct {
+		first uint64
+		last  uint64
+		pos   int64
+		n     int64
+
+		start uint64
+		count int64
+	}{
+		{1, 10, 0, 10, 1, 10},
+		{1, 10, 0, 11, 1, 10},
+		{1, 5, 0, 10, 1, 5},
+		{1, 10, 4, 10, 5, 6},
+		{1, 10, 5, 10, 6, 5},
+		{1, 10, 0, -10, 0, 0},
+		{1, 10, 1, -1, 2, -1},
+		{1, 10, 1, -10, 2, -1},
+		{1, 10, -1, 1, 10, 1},
+		{1, 10, -2, 10, 9, 2},
+		{1, 10, -1, -1, 10, -1},
+		{1, 10, -2, -10, 9, -9},
+		{1, 10, 0, -10, 0, 0},
+		{1, 10, 10, 10, 0, 0},
+		{1, 10, 0, AllEvents, 1, 10},
+		{1, 10, -1, -AllEvents, 10, -10},
+
+		{5, 10, 0, 1, 5, 1},
+	}
+
+	for _, tt := range tests {
+		start, count := math.PagerBox(tt.first, tt.last, tt.pos, tt.n)
+		if count > 0 {
+			t.Log(tt, "|", start, count, int64(start)+count-1)
+		} else {
+			t.Log(tt, "|", start, count, int64(start)+count+1)
+		}
+
+		is.Equal(start, tt.start)
+		is.Equal(count, tt.count)
+	}
+}
+
+const AppendOnly = ^uint64(0)
+const AllEvents = int64(AppendOnly >> 1)