Visual F# 100 Examples: Example 14 and 15(Pattern Matching)

Pattern matching/match with statement is similar to the switch selection statement in other programming languages. The following examples demonstrate how to use it:


Problem: Make an application that will asks a letter and displays its equivalent U. S. military phonetic alphabet.

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1. //use F# library  
2. open System  
3. //change the CLI title  
4. System.Console.Title<-"Display Military Phoenitic Alphabet"  
5. //adds color to our console application  
6. System.Console.ForegroundColor<-ConsoleColor.Blue  
7. //asks the user to enter a letter  
8. printfn "Enter a letter:"  
9. //convert the input to character and convert it to uppercase letter  
10. //this is just for comparison purpose  
11. let chrletter=Char.ToUpper(Convert.ToChar(System.Console.ReadLine()))  
12. //clear the screen     
13. System.Console.Clear()  
14. //match the value of chrletter to the ff. values  
15. match chrletter with  
16. //if the value of chrletter is a or A display Alpha  
17. | 'A' ->printfn "Alpha"  
18. //if the value of chrletter is b or B display Bravo  
19. | 'B' ->printfn "Bravo"  
20. //if the value of chrletter is c or C display Charlie  
21. | 'C' ->printfn "Charlie"  
22. //if the value of chrletter is d or D display Delta  
23. | 'D' ->printfn "Delta"  
24. //if the value of chrletter is e or E display Echo  
25. | 'E'->printfn "Echo"  
26. //if the value of chrletter is f or F display Foxtrot  
27. | 'F'->printfn "FoxTrot"  
28. //if the value of chrletter is g or G display Golf  
29. | 'G'->printfn "Golf"  
30. //if the value of chrletter is h or H display Hotel  
31. | 'H'->printfn "Hotel"  
32. //if the value of chrletter is i or I display India  
33. | 'I'->printfn "India"  
34. //if the value of chrletter is j or J display Juliet  
35. | 'J'->printfn "Juliet"  
36. //if the value of chrletter is k or K display Kilo  
37. | 'K'->printfn "Kilo"  
38. //if the value of chrletter is l or L display Lima  
39. | 'L'->printfn "Lima"  
40. //if the value of chrletter m or M display Mike  
41. | 'M'->printfn "Mike"  
42. //if the value of chrletter is n or N display November  
43. | 'N'->printfn "November"  
44. //if the value of chrletter is o or O display Oscar  
45. | 'O'->printfn "Oscar"  
46. //if the value of chrletter is p or P display Papa  
47. | 'P'->printfn "Papa"  
48. //if the value of chrletter is q or Q display Quebec  
49. | 'Q'->printfn "Quebec"  
50. //if the value of chrletter is r or R display Romeo  
51. | 'R'->printfn "Romeo"  
52. //if the value of chrletter is s or S display Sierra  
53. | 'S'->printfn "Sierra"  
54. //if the value of chrletter is t or T display Tango  
55. | 'T'->printfn "Tango"  
56. //if the value of chrletter is u or U display Uniform  
57. | 'U'->printfn "Uniform"  
58. //if the value of chrletter is v or V display Victor  
59. | 'V'->printfn "Victor"  
60. //if the value of chrletter is w or W display Whiskey  
61. | 'W'->printfn "Whiskey"  
62. //if the value of chrletter is x or X display X-Ray  
63. | 'X'->printfn "X-Ray"  
64. //if the value of chrletter is y or Y display Yankee  
65. | 'Y'->printfn "Yankee"  
66. //if the value of chrletter is z or Z display Zulu  
67. | 'Z'->printfn "Zulu"  
68. //otherwise  
69. | _ ->printfn "Invalid input"  

//use F# library
open System
//change the CLI title
System.Console.Title<-"Display Military Phoenitic Alphabet"
//adds color to our console application
System.Console.ForegroundColor<-ConsoleColor.Blue
//asks the user to enter a letter
printfn "Enter a letter:"
//convert the input to character and convert it to uppercase letter
//this is just for comparison purpose
let chrletter=Char.ToUpper(Convert.ToChar(System.Console.ReadLine()))
//clear the screen   
System.Console.Clear()
//match the value of chrletter to the ff. values
match chrletter with
//if the value of chrletter is a or A display Alpha
| 'A' ->printfn "Alpha"
//if the value of chrletter is b or B display Bravo
| 'B' ->printfn "Bravo"
//if the value of chrletter is c or C display Charlie
| 'C' ->printfn "Charlie"
//if the value of chrletter is d or D display Delta
| 'D' ->printfn "Delta"
//if the value of chrletter is e or E display Echo
| 'E'->printfn "Echo"
//if the value of chrletter is f or F display Foxtrot
| 'F'->printfn "FoxTrot"
//if the value of chrletter is g or G display Golf
| 'G'->printfn "Golf"
//if the value of chrletter is h or H display Hotel
| 'H'->printfn "Hotel"
//if the value of chrletter is i or I display India
| 'I'->printfn "India"
//if the value of chrletter is j or J display Juliet
| 'J'->printfn "Juliet"
//if the value of chrletter is k or K display Kilo
| 'K'->printfn "Kilo"
//if the value of chrletter is l or L display Lima
| 'L'->printfn "Lima"
//if the value of chrletter m or M display Mike
| 'M'->printfn "Mike"
//if the value of chrletter is n or N display November
| 'N'->printfn "November"
//if the value of chrletter is o or O display Oscar
| 'O'->printfn "Oscar"
//if the value of chrletter is p or P display Papa
| 'P'->printfn "Papa"
//if the value of chrletter is q or Q display Quebec
| 'Q'->printfn "Quebec"
//if the value of chrletter is r or R display Romeo
| 'R'->printfn "Romeo"
//if the value of chrletter is s or S display Sierra
| 'S'->printfn "Sierra"
//if the value of chrletter is t or T display Tango
| 'T'->printfn "Tango"
//if the value of chrletter is u or U display Uniform
| 'U'->printfn "Uniform"
//if the value of chrletter is v or V display Victor
| 'V'->printfn "Victor"
//if the value of chrletter is w or W display Whiskey
| 'W'->printfn "Whiskey"
//if the value of chrletter is x or X display X-Ray
| 'X'->printfn "X-Ray"
//if the value of chrletter is y or Y display Yankee
| 'Y'->printfn "Yankee"
//if the value of chrletter is z or Z display Zulu
| 'Z'->printfn "Zulu"
//otherwise
| _ ->printfn "Invalid input"

The last statement |_ is similar to the
default statement in other programming languages Switch conditional structure. It is automatically executed when no pattern match is found. Don't forget to add it at the end of every match with statement otherwise you will get an “Incomplete pattern matches on this expression” error.


Problem: Make an application that will ask the month number and display the corresponding month name and the number of days in it. Use pattern matching.

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1. //use F# library  
2. open System  
3. //change the CLI title  
4. System.Console.Title<-"Display Month Name"  
5. //adds color to our console application  
6. System.Console.ForegroundColor<-ConsoleColor.Blue  
7. System.Console.BackgroundColor<-ConsoleColor.White  
8. //asks the user to enter a month number  
9. printfn "Enter a month number(1-12):"  
10. let intmonth=Convert.ToInt32(System.Console.ReadLine())  
11. //clear the screen     
12. System.Console.Clear()  
13. //match the value of intmonth to the ff. values  
14. match intmonth with  
15. //if the value of intmonth is 1 display January  
16. | 1 ->printfn "January(31 days)"  
17. //if the value of intmonth is 2 display February  
18. | 2 ->printfn "Febrary(28/29 days)"  
19. //if the value of intmonth is 3 display March   
20. | 3 ->printfn "March(31 days)"  
21. //if the value of intmonth is 4 display April  
22. | 4 ->printfn "April(30 days)"  
23. //if the value of intmonth is 5 display May  
24. | 5 ->printfn "May(31 days)"  
25. //if the value of intmonth is 6 display June  
26. | 6 ->printfn "June(30 days)"  
27. //if the value of intmonth is 7 display July  
28. | 7 ->printfn "July(31 days)"  
29. //if the value of intmonth is 8 display August  
30. | 8 ->printfn "August(31 days)"  
31. //if the value of intmonth is 9 display September  
32. | 9 ->printfn "September(30 days)"  
33. //if the value of intmonth is 10 display October  
34. | 10 ->printfn "October(31 days)"  
35. //if the value of intmonth is 11 display November  
36. | 11 ->printfn "November(30 days)"  
37. //if the value of intmonth is 12 display December  
38. | 12->printfn "December(31 days)"  
39. //otherwise  
40. | _ ->printfn "Invalid input"  

//use F# library
open System
//change the CLI title
System.Console.Title<-"Display Month Name"
//adds color to our console application
System.Console.ForegroundColor<-ConsoleColor.Blue
System.Console.BackgroundColor<-ConsoleColor.White
//asks the user to enter a month number
printfn "Enter a month number(1-12):"
let intmonth=Convert.ToInt32(System.Console.ReadLine())
//clear the screen   
System.Console.Clear()
//match the value of intmonth to the ff. values
match intmonth with
//if the value of intmonth is 1 display January
| 1 ->printfn "January(31 days)"
//if the value of intmonth is 2 display February
| 2 ->printfn "Febrary(28/29 days)"
//if the value of intmonth is 3 display March 
| 3 ->printfn "March(31 days)"
//if the value of intmonth is 4 display April
| 4 ->printfn "April(30 days)"
//if the value of intmonth is 5 display May
| 5 ->printfn "May(31 days)"
//if the value of intmonth is 6 display June
| 6 ->printfn "June(30 days)"
//if the value of intmonth is 7 display July
| 7 ->printfn "July(31 days)"
//if the value of intmonth is 8 display August
| 8 ->printfn "August(31 days)"
//if the value of intmonth is 9 display September
| 9 ->printfn "September(30 days)"
//if the value of intmonth is 10 display October
| 10 ->printfn "October(31 days)"
//if the value of intmonth is 11 display November
| 11 ->printfn "November(30 days)"
//if the value of intmonth is 12 display December
| 12->printfn "December(31 days)"
//otherwise
| _ ->printfn "Invalid input"

That's all for now my Visual F# friends. Ciao!

Visual F# 100 Examples: Example 12 and 13

This is the continuation of our planned 100 Visual F# examples. By the way, the bugs in examples number 7 to 11 had been fixed. My apologies, I should’nt have written those without using Visual F# compiler:)


Problem: Make a console application that will asks the user to enter the day that he was born and display his character or future based on the famous nursery rhyme written in England, “Monday’s Child”.

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1. open System  
2. //changes the console application title  
3. System.Console.Title<-"Tell the Future"  
4. //adds foreground color  
5. System.Console.ForegroundColor<-ConsoleColor.Cyan  
6. printfn "What day were you born?"  
7. let strday=System.Console.ReadLine()  
8. //clears the screen  
9. System.Console.Clear()  
10. //converts the inputs to lowercase then compare it our  
11. //specified values  
12. if strday.ToLower()="monday" then  
13.     printfn "Monday's child is fair of face"  
14. else if strday.ToLower()="tuesday" then  
15.     printfn "Tuesday's child is full of grace"  
16. else if strday.ToLower()="wednesday" then  
17.     printfn "Wednesday's child is full of woe"  
18. else if strday.ToLower()="thursday" then  
19.     printfn "Thurdays's child has far to go"  
20. else if strday.ToLower()="friday" then  
21.     printfn "Friday's child is loving and giving"  
22. else if strday.ToLower()="saturday" then  
23.     printfn "Saturday's child works hard for a living"  
24. else if strday.ToLower()="sunday" then  
25.     printfn "Sunday's child is bonny and blithe and good and gay"  
26. else  
27.     printfn "Invalid input"  

open System
//changes the console application title
System.Console.Title<-"Tell the Future"
//adds foreground color
System.Console.ForegroundColor<-ConsoleColor.Cyan
printfn "What day were you born?"
let strday=System.Console.ReadLine()
//clears the screen
System.Console.Clear()
//converts the inputs to lowercase then compare it our
//specified values
if strday.ToLower()="monday" then
    printfn "Monday's child is fair of face"
else if strday.ToLower()="tuesday" then
    printfn "Tuesday's child is full of grace"
else if strday.ToLower()="wednesday" then
    printfn "Wednesday's child is full of woe"
else if strday.ToLower()="thursday" then
    printfn "Thurdays's child has far to go"
else if strday.ToLower()="friday" then
    printfn "Friday's child is loving and giving"
else if strday.ToLower()="saturday" then
    printfn "Saturday's child works hard for a living"
else if strday.ToLower()="sunday" then
    printfn "Sunday's child is bonny and blithe and good and gay"
else
    printfn "Invalid input"

Problem: Develop a console application that will asks the wind speed in kilometer per hour(kph) and display its equivalent Philippine Storm Signal number.

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1. open System  
2. //changes the console application title  
3. System.Console.Title<-"Determine Storm Signal Number"  
4. //adds foreground color  
5. System.Console.ForegroundColor<-ConsoleColor.Cyan  
6. printfn "Enter wind speed(kph):"  
7. let intspeed=Convert.ToInt32(System.Console.ReadLine())  
8. //clears the screen  
9. System.Console.Clear()  
10. //if the wind speed ranges from 30 to 60  
11. if intspeed>=30 && intspeed<=60 then  
12.     printfn "Storm signal number 1"  
13. //if the wind speed ranges from 61 to 100  
14. else if intspeed>60 && intspeed<=100 then  
15.     printfn "Storm signal number 2"  
16. //if the wind speed ranges from 101 to 185  
17. else if intspeed>100 && intspeed<=185 then  
18.     printfn "Storm signal number 3"  
19. //if the wind speed is greater than 185  
20. else if intspeed>185 then  
21. printfn "Storm signal number 4"  
22. else   
23. printfn "Invalid input"  

open System
//changes the console application title
System.Console.Title<-"Determine Storm Signal Number"
//adds foreground color
System.Console.ForegroundColor<-ConsoleColor.Cyan
printfn "Enter wind speed(kph):"
let intspeed=Convert.ToInt32(System.Console.ReadLine())
//clears the screen
System.Console.Clear()
//if the wind speed ranges from 30 to 60
if intspeed>=30 && intspeed<=60 then
    printfn "Storm signal number 1"
//if the wind speed ranges from 61 to 100
else if intspeed>60 && intspeed<=100 then
    printfn "Storm signal number 2"
//if the wind speed ranges from 101 to 185
else if intspeed>100 && intspeed<=185 then
    printfn "Storm signal number 3"
//if the wind speed is greater than 185
else if intspeed>185 then
printfn "Storm signal number 4"
else 
printfn "Invalid input"