string negator

Code:

---

Function Negate(sentence As String) As String
    ' Check if the sentence contains "not"
    If sentence.Contains("not") Then
        Return sentence.Replace("not", "").Trim()
    Else
        ' Replace specific words with their negative forms
        Dim replacements As New Dictionary(Of String, String) From {
            {"i ", "i do "},
            {"he ", "he does "},
            {" it ", " it does "},
            {"is", "is not"},
            {" am", " am not"},
            {" are", " are not"},
            {"does", "does not"},
            {"do ", "do not "},
            {"may", "may not"},
            {"might", "might not"},
            {"could", "could not"},
            {"would", "would not"},
            {"will", "will not"},
            {"has ", "has not "},
            {"have ", "have not "}
        }

        For Each kvp As KeyValuePair(Of String, String) In replacements
            sentence = sentence.Replace(kvp.Key, kvp.Value)
        Next

        If Not sentence.Contains("not") Then
            Return "not " & sentence
        End If
    End If

    Return sentence
End Function

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I wanted to point out that this code sample does not pass simple unit testing. For example:

Code:

---

Dim testSentence As String = "I am not a woman, therefore I am a man."
Dim passSentence As String = "I am a woman, therefore I am not a man."
Dim negatedTest As String = Negate(testSentence)

negatedTest.AssertEquals(testSentence) ' fails

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Demo: https://dotnetfiddle.net/BD9pfp

The reason it fails is because it incorrectly handles whitespace, it completely ignores casing, and it also fails to consider a negated word with a non-negated word in a single sentence.