fix julian examples, reference common.FloorDiv, clarify doc for FloorDiv

common/math.go

@@ -30,7 +30,7 @@ func Horner(x float64, c []float64) float64 {
 	return y
 }
 
-// FloorDiv returns the floor of x / y.
+// FloorDiv returns the integer floor of the fractional value (x / y).
 //
 // It uses integer math only, so is more efficient than using floating point
 // intermediate values.  This function can be used in many places where INT()
@@ -42,7 +42,7 @@ func FloorDiv(x, y int) int {
 	return x/y - 1
 }
 
-// FloorDiv64 returns the floor of x / y.
+// FloorDiv64 returns the integer floor of the fractional value (x / y).
 //
 // It uses integer math only, so is more efficient than using floating point
 // intermediate values.  This function can be used in many places where INT()

julian/julian.go

@@ -2,6 +2,14 @@
 // License MIT: http://www.opensource.org/licenses/MIT
 
 // Julian: Chapter 7, Julian day.
+//
+// Under "General remarks", Meeus describes the INT function as used in the
+// book.  In some contexts, math.Floor might be suitable, but I think more
+// often, the functions common.FloorDiv or common.FloorDiv64 will be more
+// appropriate.  See documentation in package common.
+//
+// On p. 63, Modified Julian Day is defined.  See constant JMod in package
+// common.
 package julian
 
 import (

julian/julian_test.go

@@ -24,9 +24,9 @@ func ExampleCalendarGregorianToJD_halley() {
 	// Example 7.c, p. 64.
 	jd1 := julian.CalendarGregorianToJD(1910, 4, 20)
 	jd2 := julian.CalendarGregorianToJD(1986, 2, 9)
-	fmt.Printf("%.0f\n", jd2-jd1)
+	fmt.Printf("%.0f days\n", jd2-jd1)
 	// Output:
-	// 27689
+	// 27689 days
 }
 
 func TestGreg(t *testing.T) {
@@ -121,9 +121,9 @@ func TestGregLeap(t *testing.T) {
 func ExampleJDToCalendar() {
 	// Example 7.c, p. 64.
 	y, m, d := julian.JDToCalendar(2436116.31)
-	fmt.Println("%d %d %.2f\n", y, m, d)
-	// Output
-	// 1957 10 4.81
+	fmt.Printf("%d %s %.2f\n", y, time.Month(m), d)
+	// Output:
+	// 1957 October 4.81
 }
 
 func TestYMD(t *testing.T) {
@@ -145,9 +145,9 @@ func TestYMD(t *testing.T) {
 
 func ExampleDayOWeek() {
 	// Example 7.e, p. 65.
-	fmt.Println(julian.DayOfWeek(2434923.5))
+	fmt.Println(time.Weekday(julian.DayOfWeek(2434923.5)))
 	// Output:
-	// 3
+	// Wednesday
 }
 
 func ExampleDayOfYear_f() {