private static IfExpression If(ListExpression list_expression)
{
if (list_expression.Items.Length > 0)
{
if (IsSymbol(list_expression.Items[0], keyword_if))
{
if (list_expression.Items.Length > 1)
{
IExpression condition = ConditionExpression(list_expression.Items[1]);
if (condition != null)
{
if (list_expression.Items.Length > 2)
{
IExpression consequent = AnalyzeExpression(list_expression.Items[2]);
if (consequent != null)
{
if (list_expression.Items.Length > 3)
{
IExpression alternative = AnalyzeExpression(list_expression.Items[3]);
if (alternative != null)
{
return new IfExpression(condition, consequent, alternative);
}
}
}
}
}
}
}
}
return null;
}
private static DefineExpression Define(ListExpression list_expression)
{
if (list_expression.Items.Length > 0)
{
if (IsSymbol(list_expression.Items[0], keyword_define))
{
if (list_expression.Items.Length > 1)
{
if (IsIdentifier(list_expression.Items[1]))
{
if (list_expression.Items.Length == 3)
{
IExpression value_expression = ValueExpression(list_expression.Items[2]);
if (value_expression != null)
{
return new DefineExpression((list_expression.Items[1] as SymbolAtom).Symbol, value_expression);
}
}
}
else
{
ListExpression function_signature = list_expression.Items[1] as ListExpression;
if (function_signature != null)
{
if (function_signature.Items.Length > 0)
{
if (function_signature.Items.All(IsIdentifier))
{
if (list_expression.Items.Length > 2)
{
var item_list = new List<IExpression>();
for (int i = 2; i < list_expression.Items.Length; i++)
{
item_list.Add(AnalyzeExpression(list_expression.Items[i]));
}
return new DefineExpression((function_signature.Items[0] as SymbolAtom).Symbol, new LambdaExpression(list_expression.Items.Skip(1).Select(exp => (exp as SymbolAtom).Symbol), item_list));
}
}
}
}
}
}
}
}
return null;
}
private static LambdaExpression Lambda(ListExpression list_expression)
{
if (list_expression.Items.Length > 0)
{
if (IsSymbol(list_expression.Items[0], keyword_lambda))
{
if (list_expression.Items.Length > 1)
{
var parameter_list = list_expression.Items[1] as ListExpression;
if (parameter_list != null)
{
if (parameter_list.Items.All(IsIdentifier))
{
if (list_expression.Items.Length > 2)
{
var item_list = new List<IExpression>();
for (int i = 2; i < list_expression.Items.Length; i++)
{
item_list.Add(AnalyzeExpression(list_expression.Items[i]));
}
return new LambdaExpression(parameter_list.Items.Select(exp => (exp as SymbolAtom).Symbol), item_list);
}
}
}
}
}
}
return null;
}