the lexicon owns the weekdays and the oblique small numbers (V-581)

Weekday names lived in four files outside internal/lexicon and each copy was
short in a different direction. The habit map had the prepositional plural of
Sunday and no dative of Wednesday. The plan refusal had the accusative of
Wednesday and not the prepositional. cmd/mavend matched the stem.

Weekdays hands out the seven nominatives whole, because every Russian case
lemmatises to one of them and the case is morph's question. WeekdayEnglish is
the half that has to be data: the vendored dictionary is Russian and leaves
mondays as it found it.

Cardinals gain the dative and instrumental of one to four. A spoken hour
declines and five upward has one oblique form for the genitive, dative and
prepositional, so pyati was already whole while dvum was missing and k dvum
chasam is an hour he says.

internal/lexicon/lexicon.go

@@ -62,7 +62,7 @@ func mustLoad() lexiconFile {
 	}
 	for _, name := range []string{
 		"interrogatives", "capture_verbs", "narrative_requests", "cardinals", "ordinals",
-		"day_offsets", "weekdays", "months_genitive", "hours_spoken",
+		"day_offsets", "weekdays", "weekdays_english", "months_genitive", "hours_spoken",
 		"not_place_after_v", "parts_of_day", "reminder_verbs", "half_hour",
 		"filler_particles", "task_done_words", "task_drop_words",
 		"confirm_yes", "confirm_no",
@@ -283,6 +283,20 @@ func DayOffsetIn(text string) (int, bool) {
 // Go's time.Weekday. An index off the end returns "".
 func Weekday(i int) string { return at("weekdays", i) }
 
+// Weekdays returns the seven Russian names in one slice, Sunday first, for a
+// caller matching a token against all of them rather than rendering one. Only
+// the nominative is here: every other case lemmatises to it, so an oblique form
+// is morph's question and not a second list (V-581).
+func Weekdays() []string { return words("weekdays") }
+
+// WeekdayEnglish reports the Go time.Weekday index an English weekday names,
+// singular or plural. English needs the list that Russian does not, because the
+// vendored dictionary is Russian and leaves "mondays" as it found it.
+func WeekdayEnglish(word string) (int, bool) {
+	n, ok := ru.Sets["weekdays_english"].Values[norm(word)]
+	return n, ok
+}
+
 // MonthGenitive returns the month name a date takes — "10 июля", not "июль".
 // The set is 1-indexed, so MonthGenitive(int(t.Month())) is the whole call.
 func MonthGenitive(m int) string { return at("months_genitive", m) }

internal/lexicon/lexicon_ru_v1.json

@@ -56,13 +56,13 @@
       }
     },
     "cardinals": {
-      "note": "Number words as spoken, with the gender variants Russian requires (один/одна/одно and два/две agree with the noun that follows) and the oblique forms, because a spoken time declines: \"в семь\", \"к семи\", \"около семи\" are three forms of one hour (Vikunja #530). Values are the number itself. Twenties and up are compounds and are read as their parts, so only the round members are listed.",
+      "note": "Number words as spoken, with the gender variants Russian requires (один/одна/одно and два/две agree with the noun that follows) and the oblique forms, because a spoken time declines: \"в семь\", \"к семи\", \"около семи\" are three forms of one hour (Vikunja #530). Values are the number itself. Twenties and up are compounds and are read as their parts, so only the round members are listed. From five up one oblique form serves the genitive, dative and prepositional, so \"пяти\" is the whole set; one to four decline separately and carry the dative and instrumental of their own, because \"к двум часам\" and \"к трём\" are hours he says (V-581).",
       "values": {
         "ноль": 0, "нуль": 0, "zero": 0,
-        "один": 1, "одна": 1, "одно": 1, "одного": 1, "одной": 1, "одну": 1, "one": 1,
-        "два": 2, "две": 2, "двух": 2, "two": 2,
-        "три": 3, "трёх": 3, "трех": 3, "three": 3,
-        "четыре": 4, "четырёх": 4, "четырех": 4, "four": 4,
+        "один": 1, "одна": 1, "одно": 1, "одного": 1, "одной": 1, "одну": 1, "одному": 1, "одним": 1, "one": 1,
+        "два": 2, "две": 2, "двух": 2, "двум": 2, "двумя": 2, "two": 2,
+        "три": 3, "трёх": 3, "трех": 3, "трём": 3, "трем": 3, "тремя": 3, "three": 3,
+        "четыре": 4, "четырёх": 4, "четырех": 4, "четырём": 4, "четырем": 4, "четырьмя": 4, "four": 4,
         "пять": 5, "пяти": 5, "five": 5,
         "шесть": 6, "шести": 6, "six": 6,
         "семь": 7, "семи": 7, "seven": 7,
@@ -111,6 +111,18 @@
         "четверг", "пятница", "суббота"
       ]
     },
+    "weekdays_english": {
+      "note": "The English weekday names with their Go time.Weekday index, plus the plural a habit is spoken in (\"on mondays\"). English is listed as words where Russian is not, because the vendored dictionary is Russian: it lemmatises \"пятницу\" to \"пятница\" on its own and leaves \"mondays\" alone (V-581). So the Russian side of a weekday match is grammar and the English side is data.",
+      "values": {
+        "sunday": 0, "sundays": 0,
+        "monday": 1, "mondays": 1,
+        "tuesday": 2, "tuesdays": 2,
+        "wednesday": 3, "wednesdays": 3,
+        "thursday": 4, "thursdays": 4,
+        "friday": 5, "fridays": 5,
+        "saturday": 6, "saturdays": 6
+      }
+    },
     "months_genitive": {
       "note": "The form a date takes: \"10 июля\", not \"июль\". 1-indexed, so slot 0 is empty and month numbers need no arithmetic.",
       "words": [

internal/lexicon/lexicon_test.go

@@ -36,6 +36,46 @@ func TestClosedSetsAreComplete(t *testing.T) {
 	if _, ok := Cardinal("бэкап"); ok {
 		t.Error("Cardinal must not answer for a word that is not a number")
 	}
+
+	// A spoken hour declines, and one to four decline further than the rest:
+	// "к двум часам" and "к трём" are hours, and only the dative says so (V-581).
+	for _, tc := range []struct {
+		word string
+		want int
+	}{
+		{"одному", 1}, {"двум", 2}, {"двумя", 2}, {"трём", 3}, {"трем", 3},
+		{"четырём", 4}, {"четырем", 4}, {"пяти", 5}, {"семи", 7},
+	} {
+		if got, ok := Cardinal(tc.word); !ok || got != tc.want {
+			t.Errorf("Cardinal(%q) = %d, %v; want %d, true", tc.word, got, ok, tc.want)
+		}
+	}
+}
+
+// TestWeekdaysAreOneList — the second copy of a closed class is the bug (V-581).
+// Weekdays lived in four files outside this one, so the list is handed out whole
+// and the English forms, which the Russian dictionary cannot lemmatise, are here.
+func TestWeekdaysAreOneList(t *testing.T) {
+	days := Weekdays()
+	if len(days) != 7 || days[0] != "воскресенье" || days[1] != "понедельник" {
+		t.Fatalf("Weekdays() = %v; want the seven, Sunday first", days)
+	}
+	for i, name := range days {
+		if Weekday(i) != name {
+			t.Errorf("Weekdays()[%d] = %q, but Weekday(%d) = %q", i, name, i, Weekday(i))
+		}
+	}
+	for _, tc := range []struct {
+		word string
+		want int
+	}{{"sunday", 0}, {"monday", 1}, {"mondays", 1}, {"Friday", 5}, {"saturdays", 6}} {
+		if got, ok := WeekdayEnglish(tc.word); !ok || got != tc.want {
+			t.Errorf("WeekdayEnglish(%q) = %d, %v; want %d, true", tc.word, got, ok, tc.want)
+		}
+	}
+	if _, ok := WeekdayEnglish("понедельник"); ok {
+		t.Error("WeekdayEnglish answered for a Russian word; that side is morph's")
+	}
 }
 
 // TestDayOffsetHasNoOrderingTrap — the defect a lookup removes. The callers this