/// <summary>
/// Takes a sequence of quotes and an expression to quote and returns quoted expression.
/// </summary>
/// <param name="quoteList">A list of quotes.</param>
/// <param name="expression">An expression to quote.</param>
/// <returns>Quoted expression.</returns>
private static IExpression QuoteExpression(List <IExpression> quoteList, IExpression expression)
{
AbstractQuotation quotedExpression = null;
var quoteListCount = quoteList.Count;
for (int i = 0; i < quoteListCount; ++i)
{
// We process them in an inside-out manner.
var quote = quoteList[quoteListCount - i - 1];
// isQuoted is true here, since the expression could be a combination, and we want
// any combination within that combination to be converted to lists when we quote
// it.
if (quote is ScmQuoteSpecialForm)
{
quotedExpression = new ScmQuoteSpecialForm(QuotationSyntacticSugar(expression, true));
}
else if (quote is ScmUnquoteSpecialForm)
{
quotedExpression = new ScmUnquoteSpecialForm(QuotationSyntacticSugar(expression, true));
}
else if (quote is ScmQuasiquoteSpecialForm)
{
quotedExpression = new ScmQuasiquoteSpecialForm(QuotationSyntacticSugar(expression, true));
}
expression = quotedExpression;
}
return(quotedExpression);
}
/// <summary>
/// This methods analyses the given tokens and produces a list of combinations
/// and expressions that can be parsed further for syntax consistency etc.
/// </summary>
/// <param name="tokens">A list of tokens.</param>
/// <returns>A list of combinations and expressions.</returns>
private static List <IExpression> CombineExpressions(List <Token> tokens)
{
CheckParanthesisBalance(tokens);
var program = new List <IExpression> ();
var eStack = new Stack <IExpression> ();
ScmCombination currentCombination = null;
for (int i = 0; i < tokens.Count; ++i)
{
var token = tokens[i];
if (token is BeginToken)
{
if (currentCombination != null)
{
eStack.Push(currentCombination);
}
currentCombination = new ScmCombination(token);
}
else if (token is EndToken)
{
IExpression cExpr = currentCombination as IExpression;
currentCombination = cExpr as ScmCombination;
if (eStack.Count > 0)
{
var stackExprOnTop = eStack.Peek() as ScmCombination;
stackExprOnTop.Expressions.Add(currentCombination);
currentCombination = eStack.Pop() as ScmCombination;
}
else
{
program.Add(currentCombination);
currentCombination = null;
}
}
else
{
if (token is SymbolToken)
{
IExpression scmSymbol = new ScmSymbol(token);
AddExpression(scmSymbol, currentCombination, program);
}
else if (token is NumberToken)
{
IExpression scmNumber = NumberParser(token as NumberToken);
AddExpression(scmNumber, currentCombination, program);
}
else if (token is StringToken)
{
IExpression scmString = new ScmString(token);
AddExpression(scmString, currentCombination, program);
}
else if (token is DotToken)
{
IExpression scmString = new ScmDotModifier(token);
AddExpression(scmString, currentCombination, program);
}
else if (token is QuoteToken || token is QuasiquoteToken || token is UnquoteToken)
{
IExpression scmQuote = null;
if (token is QuoteToken)
{
scmQuote = new ScmQuoteSpecialForm(null);
}
else if (token is UnquoteToken)
{
scmQuote = new ScmUnquoteSpecialForm(null);
}
else
{
scmQuote = new ScmQuasiquoteSpecialForm(null);
}
AddExpression(scmQuote, currentCombination, program);
}
}
}
return(QuotationSyntacticSugar(program, false));
}