Just another update

Task/Five-weekends/00DESCRIPTION

@@ -12,3 +12,8 @@ The month of October in 2010 has five Fridays, five Saturdays, and five Sundays.
 '''Extra credit'''
 
 Count and/or show all of the years which do not have at least one five-weekend month (there should be 29).
+
+;See also
+* [[Day of the week]]
+* [[Last Friday of each month]]
+* [[Find last sunday of each month]]

Task/Five-weekends/00META.yaml

@@ -0,0 +1,5 @@
+---
+category:
+- Date and time
+- Puzzles
+note: Five weekends

Task/Five-weekends/AWK/five-weekends.awk

@@ -0,0 +1,56 @@
+# usage:  awk -f 5weekends.awk  cal.txt
+
+# Filter a file of month-calendars, such as
+# ...
+##        January 1901
+##    Mo Tu We Th Fr Sa Su
+##        1  2  3  4  5  6
+##     7  8  9 10 11 12 13
+##    14 15 16 17 18 19 20
+##    21 22 23 24 25 26 27
+##    28 29 30 31
+# ...
+##         March 1901
+##    Mo Tu We Th Fr Sa Su
+##                 1  2  3
+##     4  5  6  7  8  9 10
+##    11 12 13 14 15 16 17
+##    18 19 20 21 22 23 24
+##    25 26 27 28 29 30 31
+# ...
+# This file is generated by a script for the unix-shell,
+# see http://rosettacode.org/wiki/Five_weekends#UNIX_Shell
+
+BEGIN   { print("# Month with 5 weekends:")
+          badYears = numW5 = 0;
+          lastW5 = -1
+        }
+
+0+$2>33 { if( $2>currYear ) {       # calendar-header: month, year
+            if( lastW5==numW5 ) {
+              badYears++; sep="\n"
+              if( badYears % 10 ) { sep=" " }
+              bY=bY currYear sep;   # collect years in string
+            ##print badYears,":", currYear
+            }
+            lastW5=numW5
+          }
+          WE=0; currYear=$2; currMY = $1 " " $2;
+        ##print currMY;
+          next
+        }
+
+/^Mo/   { next }                    # skip lines with weekday-names
+
+        { $0 = substr($0,13) }      # cut inputline, leave  Fr,Sa,Su only
+
+NF>2    { WE++;                     # 3 fields left => complete weekend found
+          if( WE>4 ) {
+            numW5++; printf("%4d : %s\n", numW5, currMY)
+          }
+        }
+
+END     { print("# Found", numW5, "month with 5 weekends.")
+          print("# Found", badYears, "years with no month having 5 weekends:")
+          print(bY)
+        }

Task/Five-weekends/D/five-weekends-2.d

@@ -1,16 +1,16 @@
-import std.stdio, std.datetime, std.traits;
-
 void main() {
+    import std.stdio, std.datetime, std.traits;
+
     enum first_year = 1900;
     enum last_year = 2100;
 
-    int totalNo5Weekends;
-    const(Date)[] fiveWeekendMonths;
-    foreach (year; first_year .. last_year + 1) {
+    uint totalNo5Weekends;
+    immutable(Date)[] fiveWeekendMonths;
+    foreach (immutable year; first_year .. last_year + 1) {
         bool has5Weekends = false;
 
-        foreach (month; [EnumMembers!Month]) {
-            const firstDay = Date(year, month, 1);
+        foreach (immutable month; EnumMembers!Month) {
+            immutable firstDay = Date(year, month, 1);
             if (firstDay.daysInMonth == 31 &&
                 firstDay.dayOfWeek == DayOfWeek.fri) {
                 has5Weekends = true;
@@ -24,11 +24,11 @@ void main() {
 
     writefln("Total 5-weekend months between %d and %d: %d",
              first_year, last_year, fiveWeekendMonths.length);
-    foreach (date; fiveWeekendMonths[0 .. 5])
-        writeln(date.month, " ", date.year);
-    writeln("...");
-    foreach (date; fiveWeekendMonths[$ - 5 .. $])
-        writeln(date.month, " ", date.year);
+    foreach (immutable date; fiveWeekendMonths[0 .. 5])
+        writeln(date.month, ' ', date.year);
+    "...".writeln;
+    foreach (immutable date; fiveWeekendMonths[$ - 5 .. $])
+        writeln(date.month, ' ', date.year);
 
     writeln("\nTotal number of years with no 5-weekend months: ",
             totalNo5Weekends);

Task/Five-weekends/Racket/five-weekends.rkt

@@ -0,0 +1,26 @@
+#lang racket
+(require srfi/19)
+
+(define long-months '(1 3 5 7 8 10 12))
+(define days #(sun mon tue wed thu fri sat))
+
+(define (week-day date)
+  (vector-ref days (date-week-day date)))
+
+(define (five-weekends-a-month start end)
+  (for*/list ([year (in-range start (+ end 1))]
+              [month long-months]
+              [date (in-value (make-date 0 0 0 0 31 month year 0))]
+              #:when (eq? (week-day date) 'sun))
+    date))
+
+(define weekends (five-weekends-a-month 1900 2100))
+(define count (length weekends))
+
+(displayln (~a "There are " count " weeks with five weekends."))
+(displayln "The first five are: ")
+(for ([w (take weekends 5)])
+  (displayln (date->string w "~b ~Y")))
+(displayln "The last five are: ")
+(for ([w (drop weekends (- count 5))])
+  (displayln (date->string w "~b ~Y")))

Task/Five-weekends/Ruby/five-weekends.rb

@@ -1,11 +1,13 @@
 require 'date'
+# The only case where the month has 5 weekends is when the last day
+# of the month falls on a Sunday and the month has 31 days.
 
-# if the last day of the month falls on a Sunday and the month has 31 days,
-# this is the only case where the month has 5 weekends.
-start = Date.parse("1900-01-01")
-stop  = Date.parse("2100-12-31")
-dates = (start..stop).find_all do |day|
-  day.mday == 31 and day.wday == 0 # Ruby 1.9: and day.sunday?
+dates = []
+1900.upto(2100) do |year|
+  1.upto(12) do |month|
+    d = Date.new(year, month, -1) # -1 is last day of month
+    dates << d if d.sunday? && d.day == 31
+  end
 end
 
 puts "There are #{dates.size} months with 5 weekends from 1900 to 2100:"

Task/Five-weekends/UNIX-Shell/five-weekends.sh

@@ -0,0 +1,12 @@
+echo "Creating cal-file..."
+echo > cal.txt
+for ((y=1900; y <= 2100; y++)); do
+  for ((m=1; m <= 12; m++)); do
+   #echo $m $y
+    cal -m $m $y >> cal.txt
+  done
+done
+ls -la cal.txt
+
+echo "Looking for month with 5 weekends:"
+awk -f 5weekends.awk  cal.txt

Task/Five-weekends/XPL0/five-weekends.xpl0

@@ -1,7 +1,7 @@
 include c:\cxpl\codes;                  \intrinsic 'code' declarations
 
 
-proc    WeekDay(Year, Month, Day);      \Return day of week (0=Sat 1=Sun..6=Fri)
+func    WeekDay(Year, Month, Day);      \Return day of week (0=Sat 1=Sun..6=Fri)
 int     Year, Month, Day;
 [if Month<=2 then [Month:= Month+12;  Year:= Year-1];
 return rem((Day + (Month+1)*26/10 + Year + Year/4 + Year/100*6 + Year/400) / 7);