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Introduction
Spelling and grammar are a headache, especially for a bi-lingual person such as me. I am quite good with spelling, but grammar not that much. Today, you will learn how to create your own spelling checker.
Our Project
The project is nothing spectacular. There are simply two buttons on the form, as shown in Figure 1:
Figure 1: Our Design
Add a new Class and name it ‘Spell.’ Add the following Namespaces to the Spell class:
Imports System.IO Imports System.Text.RegularExpressions
The System.IO namespace is responsible for reading and writing the files. You will read a file containing some text a bit later in this example. The System.Text.RegularExpressions namespace allows you to manipulate words and phrases.
Add the following fields to the class:
Private strLetters As String = "abcdefghijklmnopqrstuvwxyz"
Private regWord As New Regex("[a-z]+", RegexOptions.Compiled)
Private dicDictionary As New Dictionary(Of [String], Integer)()
strLetters contains all the alphabetic letters that we will work with. The regWord object will be used to identify the words that need to be checked for spelling and manipulate them. dicDictionary contains the correct words to be checked against. Add the Constructor:
Public Sub New()
Dim strFile As String = File.ReadAllText("Dictionary.txt")
Dim lstWords As List(Of String) = _
strFile.Split(New String() {vbLf}, _
StringSplitOptions.RemoveEmptyEntries).ToList()
For Each strWord As String In lstWords
Dim strTrim As String = strWord.Trim().ToLower()
If regWord.IsMatch(strTrim) Then
If dicDictionary.ContainsKey(strTrim) Then
dicDictionary(strTrim) += 1
Else
dicDictionary.Add(strTrim, 1)
End If
End If
Next
End Sub
When the Spell class is instantiated, the Dictionary.txt file gets read and formatted and the contents get stored inside the dicDictionary object. Add the Prepare Function:
Private Function Prepare(strWord As String) As List(Of String)
Dim lstParts = New List(Of Tuple(Of String, String))()
Dim lstInverts = New List(Of String)()
Dim lstDeletions = New List(Of String)()
Dim lstReplaces = New List(Of String)()
Dim lstInsertions = New List(Of String)()
' Splits '
For p As Integer = 0 To strWord.Length - 1
Dim tParts = New Tuple(Of String, String)
(strWord.Substring(0, p), strWord.Substring(p))
lstParts.Add(tParts)
Next
' Transposes '
For i As Integer = 0 To lstParts.Count - 1
Dim strOne As String = lstParts(i).Item1
Dim strTwo As String = lstParts(i).Item2
If strTwo.Length > 1 Then
lstInverts.Add(strOne + strTwo(1) + strTwo(0) & _
strTwo.Substring(2))
End If
Next
' Deletes '
For d As Integer = 0 To lstParts.Count - 1
Dim strOne As String = lstParts(d).Item1
Dim strTwo As String = lstParts(d).Item2
If Not String.IsNullOrEmpty(strTwo) Then
lstDeletions.Add(strOne & strTwo.Substring(1))
End If
Next
' Replaces '
For r As Integer = 0 To lstParts.Count - 1
Dim strOne As String = lstParts(r).Item1
Dim strTwo As String = lstParts(r).Item2
If Not String.IsNullOrEmpty(strTwo) Then
For Each letter As Char In strLetters
lstReplaces.Add((strOne & letter) + _
strTwo.Substring(1))
Next
End If
Next
' Inserts '
For i As Integer = 0 To lstParts.Count - 1
Dim strOne As String = lstParts(i).Item1
Dim strTwo As String = lstParts(i).Item2
For Each letter As Char In strLetters
lstInsertions.Add(Convert.ToString
(strOne & letter) & strTwo)
Next
Next
Return lstDeletions.Union(lstInverts)
.Union(lstReplaces).Union(lstInsertions).ToList()
End Function
The Prepare Function identifies the given word’s broken pieces. These pieces could be a misplaced letter, a missing letter, or an accidentally swapped letter. Once all the options have been considered and processed, it returns a list containing possible words that could match the wrongly spelled word. Add the final Function:
Public Function Fix(strWord As String) As String
If String.IsNullOrEmpty(strWord) Then
Return strWord
End If
strWord = strWord.ToLower()
If dicDictionary.ContainsKey(strWord) Then
Return strWord
End If
Dim lstWords As List(Of [String]) = Prepare(strWord)
Dim dicPotential As New Dictionary(Of String, Integer)()
For Each strVariation As String In lstWords
If dicDictionary.ContainsKey(strVariation) AndAlso _
Not dicPotential.ContainsKey(strVariation) Then
dicPotential.Add(strVariation, dicDictionary(strVariation))
End If
Next
If dicPotential.Count > 0 Then
Return dicPotential.OrderByDescending _
(Function(x) x.Value).First().Key
End If
For Each sWord As String In lstWords
For Each strVariation As String In Prepare(sWord)
If dicDictionary.ContainsKey(strVariation) AndAlso _
Not dicPotential.ContainsKey(strVariation) Then
dicPotential.Add(strVariation, dicDictionary(strVariation))
End If
Next
Next
Return If((dicPotential.Count > 0), _
dicPotential.OrderByDescending(Function(x) x.Value) _
.First().Key, strWord)
End Function
The Fix Function takes the received word and compares it with a correct similar word.
Add the following code behind the Button on Form1 labeled ‘Words:’
Private Sub Button1_Click(sender As Object, e As EventArgs)_
Handles Button1.Click
Dim sEngine As New Spell()
Dim strWord As String = ""
strWord = "spellling"
Console.WriteLine("{0} => {1}", strWord, _
sEngine.Fix(strWord))
strWord = "Hannes"
Console.WriteLine("{0} => {1}", strWord, _
sEngine.Fix(strWord))
strWord = "supposidly"
Console.WriteLine("{0} => {1}", strWord, _
sEngine.Fix(strWord))
Console.Read()
End Sub
The preceding code is quite self-explanatory.
Add the following code behind the remaining button labeled ‘Sentences:’
Private Sub Button2_Click(sender As Object, e As EventArgs) _
Handles Button2.Click
Dim sEngine As New Spell()
Dim strSentence As String = "I cann niot spel niceely"
Dim strCorrection As String = ""
For Each wWord As String In strSentence.Split(" "c)
strCorrection += " " + sEngine.Fix(wWord)
Next
Console.WriteLine(Convert.ToString("Did you mean:") _
& strCorrection)
Console.Read()
End Sub
This code looks similar to the previous code except for the part that includes a loop. The For Each loop loops through each word in the given sentence.
Download the Code
You can download the code to accompany this article from the link below.
Conclusion
As you can see, creating a spell checker is quite simple. All you need is a bit of logic.
