public void ParseExpression()
{
string expression = "(Levenstein * MinLength) + (FirstContains * MinLength * 2) + (Equality * MinLength * 4)";
string parsedExpression = StringComparisonExpression.Create(expression).Print();
Assert.AreEqual(expression, parsedExpression);
}
protected virtual Expression VisitStringComparisonExpression(StringComparisonExpression expression)
{
var toLower = expression.Comparison.HasValue && expression.Comparison.Value == StringComparison.OrdinalIgnoreCase;
_expression.Append('(');
if (toLower)
{
_expression.Append("LOWER(");
Visit(expression.Left);
_expression.Append(')');
}
else
{
Visit(expression.Left);
}
switch (expression.Operation)
{
case ExpressionType.Equal:
_expression.Append(" = ");
break;
case ExpressionType.NotEqual:
_expression.Append(" != ");
break;
case ExpressionType.LessThan:
_expression.Append(" < ");
break;
case ExpressionType.LessThanOrEqual:
_expression.Append(" <= ");
break;
case ExpressionType.GreaterThan:
_expression.Append(" > ");
break;
case ExpressionType.GreaterThanOrEqual:
_expression.Append(" >= ");
break;
}
if (toLower)
{
_expression.Append("LOWER(");
Visit(expression.Right);
_expression.Append(')');
}
else
{
Visit(expression.Right);
}
_expression.Append(')');
return(expression);
}
/// <summary>
/// Converts String.Compare expression to StringComparisonExpression
/// </summary>
/// <param name="leftString">String expression on the left side of the comparison</param>
/// <param name="rightString">String expression on the right side of the comparison</param>
/// <param name="operation">Comparison operation being performed</param>
/// <param name="number">Number that String.Compare was being compared to, typically 0, 1, or -1.</param>
private Expression ConvertStringCompareExpression(Expression leftString, Expression rightString,
ExpressionType operation, int number)
{
if (number == 1)
{
if ((operation == ExpressionType.LessThan) || (operation == ExpressionType.NotEqual))
{
operation = ExpressionType.LessThanOrEqual;
}
else if ((operation == ExpressionType.Equal || operation == ExpressionType.GreaterThanOrEqual))
{
operation = ExpressionType.GreaterThan;
}
else
{
// Always evaluates to true or false regardless of input, so return a constant expression
return(System.Linq.Expressions.Expression.Constant(operation == ExpressionType.LessThanOrEqual,
typeof(bool)));
}
}
else if (number == -1)
{
if ((operation == ExpressionType.GreaterThan) || (operation == ExpressionType.NotEqual))
{
operation = ExpressionType.GreaterThanOrEqual;
}
else if ((operation == ExpressionType.Equal || operation == ExpressionType.LessThanOrEqual))
{
operation = ExpressionType.LessThan;
}
else
{
// Always evaluates to true or false regardless of input, so return a constant expression
return(System.Linq.Expressions.Expression.Constant(operation == ExpressionType.GreaterThanOrEqual,
typeof(bool)));
}
}
else if (number > 1)
{
// Always evaluates to true or false regardless of input, so return a constant expression
return(System.Linq.Expressions.Expression.Constant(
(operation == ExpressionType.NotEqual) || (operation == ExpressionType.LessThan) || (operation == ExpressionType.LessThanOrEqual),
typeof(bool)));
}
else if (number < -1)
{
// Always evaluates to true or false regardless of input, so return a constant expression
return(System.Linq.Expressions.Expression.Constant(
(operation == ExpressionType.NotEqual) || (operation == ExpressionType.GreaterThan) || (operation == ExpressionType.GreaterThanOrEqual),
typeof(bool)));
}
// If number == 0 we just leave operation unchanged
return(StringComparisonExpression.Create(operation, leftString, rightString));
}
public void InternalRankWords()
{
string expression = "(Levenstein * MinLength) + (FirstContains * MinLength * 2) + (Equality * MinLength * 4)";
string word1 = "apple";
string word2 = "maple";
double rank = StringComparisonExpression.Create(expression).RateWordSimilarity(word1, word2);
double expectedRank = 3.0d;
Assert.AreEqual(expectedRank, rank);
}
public void InternalRankSentences()
{
string expression = "(Levenstein * MinLength) + (FirstContains * MinLength * 2) + (Equality * MinLength * 4)";
string sentence1 = "Pinus torreyana var. insularis";
string sentence2 = "Mt. Atlas mastic tree";
double rank = StringComparisonExpression.Create(expression).RateSentenceSimilarity(sentence1, sentence2);
double expectedRank = 3.5000000000000004d;
Assert.AreEqual(expectedRank, rank);
}
protected virtual Expression VisitStringComparisonExpression(StringComparisonExpression expression)
{
_expression.Append('(');
VisitExpression(expression.Left);
switch (expression.Operation)
{
case ExpressionType.Equal:
_expression.Append(" = ");
break;
case ExpressionType.NotEqual:
_expression.Append(" != ");
break;
case ExpressionType.LessThan:
_expression.Append(" < ");
break;
case ExpressionType.LessThanOrEqual:
_expression.Append(" <= ");
break;
case ExpressionType.GreaterThan:
_expression.Append(" > ");
break;
case ExpressionType.GreaterThanOrEqual:
_expression.Append(" >= ");
break;
}
VisitExpression(expression.Right);
_expression.Append(')');
return(expression);
}
/// <summary>
/// Converts String.Compare expression to StringComparisonExpression
/// </summary>
/// <param name="leftString">String expression on the left side of the comparison</param>
/// <param name="rightString">String expression on the right side of the comparison</param>
/// <param name="operation">Comparison operation being performed</param>
/// <param name="number">Number that String.Compare was being compared to, typically 0, 1, or -1.</param>
/// <param name="comparisonExpression">Indicated the comparison type. Most commonly used with case insensitive comparisons</param>
private Expression ConvertStringCompareExpression(Expression leftString, Expression rightString,
ExpressionType operation, int number, ConstantExpression comparisonExpression)
{
if (number == 1)
{
if ((operation == ExpressionType.LessThan) || (operation == ExpressionType.NotEqual))
{
operation = ExpressionType.LessThanOrEqual;
}
else if ((operation == ExpressionType.Equal || operation == ExpressionType.GreaterThanOrEqual))
{
operation = ExpressionType.GreaterThan;
}
else
{
// Always evaluates to true or false regardless of input, so return a constant expression
return(Expression.Constant(operation == ExpressionType.LessThanOrEqual,
typeof(bool)));
}
}
else if (number == -1)
{
if ((operation == ExpressionType.GreaterThan) || (operation == ExpressionType.NotEqual))
{
operation = ExpressionType.GreaterThanOrEqual;
}
else if ((operation == ExpressionType.Equal || operation == ExpressionType.LessThanOrEqual))
{
operation = ExpressionType.LessThan;
}
else
{
// Always evaluates to true or false regardless of input, so return a constant expression
return(Expression.Constant(operation == ExpressionType.GreaterThanOrEqual, typeof(bool)));
}
}
else if (number > 1)
{
// Always evaluates to true or false regardless of input, so return a constant expression
return(Expression.Constant(
(operation == ExpressionType.NotEqual) || (operation == ExpressionType.LessThan) || (operation == ExpressionType.LessThanOrEqual),
typeof(bool)));
}
else if (number < -1)
{
// Always evaluates to true or false regardless of input, so return a constant expression
return(Expression.Constant(
(operation == ExpressionType.NotEqual) || (operation == ExpressionType.GreaterThan) || (operation == ExpressionType.GreaterThanOrEqual),
typeof(bool)));
}
// If number == 0 we just leave operation unchanged
StringComparison?comparison = null;
if (comparisonExpression != null)
{
comparison = (StringComparison)comparisonExpression.Value;
if (comparison != StringComparison.Ordinal && comparison != StringComparison.OrdinalIgnoreCase)
{
var msg = string.Format("String comparison option {0} is not supported", comparison);
throw new NotSupportedException(msg);
}
}
return(StringComparisonExpression.Create(operation, leftString, rightString, comparison));
}
