/// <summary>
/// Appends numbers indicating the block a statement belongs to.
/// <remarks>
/// A statement written in the format:
///
/// > var nested = from x in a
/// > from y in b
/// > select x + y;
/// >
/// > var fetch = from x in nested
/// > from y in b
/// > select x + y;
///
/// will be rewritten as:
///
/// > a.SelectMany(
/// > x => b,
/// > x, y => x + y
/// > ).SelectMany(
/// > x => b
/// > x, y => x + y
/// > );
///
/// Because there are two variables named "x", and these
/// expressions are written inline, we need to number them,
/// in case they end up in the same applicative group.
/// </remarks>
/// </summary>
public static IEnumerable <QueryStatement> NumberBlocks(List <QueryStatement> statements)
{
var blockNumber = 0;
var statementCounter = 0;
var numStatements = statements.Count();
var isFirst = true;
foreach (var statement in statements)
{
statementCounter++;
// SplitBind functions that take one non-transparent parameter are binding the entire result from another monad.
// This will hide any variables that were in scope in that monad.
statement.StartsBlock = isFirst;
if (statement.Match(
bind => bind.BindVariables.ParameterNames.Count == 1 &&
!ParseExpression.IsTransparent(bind.Expressions.Bind.Parameters.First()),
let => false)
)
{
blockNumber++;
statement.StartsBlock = true;
}
statement.BlockNumber = blockNumber;
if (statementCounter == numStatements)
{
statement.IsFinal = true;
}
isFirst = false;
yield return(statement);
}
}
/// <summary>
/// We only want to rewrite transparent identifier accessors.
/// </summary>
protected override Expression VisitMember(MemberExpression node)
{
if (ParseExpression.IsFromTransparent(node) && !ParseExpression.IsTransparentMember(node))
{
return(RewritePropertyAccess(node));
}
return(base.VisitMember(node));
}
/// <summary>
/// Gets the variables in a (bind, project) pair.
/// </summary>
private static QueryStatement GetVariables(BindProjectPair pair)
{
var project = pair.Project;
var isLet = project.Parameters.Any(param => param.Name.StartsWith(LET_PREFIX));
if (isLet)
{
var letParam = project.Parameters.ElementAt(1);
var letName = letParam.Name;
var originalName = Regex.Split(letName, LET_PREFIX)[1];
var letExpression = Expression.Lambda(project.Body, project.Parameters.First(),
Expression.Parameter(letParam.Type, originalName));
var letVariables = ParseExpression.GetExpressionVariables(letExpression);
return(new LetStatement(originalName, letExpression, letVariables));
}
var bindVars = ParseExpression.GetExpressionVariables(pair.Bind);
var projectVars = ParseExpression.GetExpressionVariables(project);
return(new BindProjectStatement(pair, bindVars, projectVars)
{
IsSelect = pair.IsSelect
});
}
