diff --git a/libwccl/ops/functions/bool/iteration.cpp b/libwccl/ops/functions/bool/iteration.cpp
index c91fc17ebf78efe9c2cf2ff1f387d438876cc6cb..cb2034a70c7a8f159f34b0bd5541a04241e4b7c1 100644
--- a/libwccl/ops/functions/bool/iteration.cpp
+++ b/libwccl/ops/functions/bool/iteration.cpp
@@ -25,8 +25,11 @@ std::ostream& Iteration::write_to(std::ostream& os) const
Iteration::BaseRetValPtr Iteration::apply_internal(const FunExecContext& context) const
{
+ // Set iteration variable to Nowhere
+ // Should be overridden if succeeded
const boost::shared_ptr<Position>& iter_var =
context.variables()->get_fast(iter_var_acc_);
+ iter_var->set_value(Position::Nowhere);
const SentenceContext& sc = context.sentence_context();
// Proceed only if range extremes are not "nowhere".
const boost::shared_ptr<const Position>& range_left =
@@ -35,7 +38,8 @@ Iteration::BaseRetValPtr Iteration::apply_internal(const FunExecContext& context
const boost::shared_ptr<const Position>& range_right =
right_pos_expr_->apply(context);
int left, right;
- if (sc.validate_range(*range_left, *range_right, left, right)) {
+ if (sc.validate_range(*range_left, *range_right,
+ left, right, may_cross)) {
// Change range from absolute to relative and iterate
left -= sc.get_position();
right -= sc.get_position();
@@ -44,7 +48,7 @@ Iteration::BaseRetValPtr Iteration::apply_internal(const FunExecContext& context
}
}
}
- // In case of failure, set iteration variable to Nowhere and return False
+ // Failure. Make sure iteration variable points Nowhere and return False
iter_var->set_value(Position::Nowhere);
return Predicate::False(context);
}
diff --git a/libwccl/ops/functions/bool/iteration.h b/libwccl/ops/functions/bool/iteration.h
index dee6c88676ed6e0ad8272f6094021922f435137c..cb96a2e59a8c8841a7670362fc2bc636a8967221 100644
--- a/libwccl/ops/functions/bool/iteration.h
+++ b/libwccl/ops/functions/bool/iteration.h
@@ -28,16 +28,19 @@ protected:
const PosFunctionPtr right_pos_expr_;
const VariableAccessor<Position> iter_var_acc_;
const BoolFunctionPtr evaluating_expr_;
+ const bool may_cross;
Iteration(
const PosFunctionPtr& left_pos_expr,
const PosFunctionPtr& right_pos_expr,
const VariableAccessor<Position>& iter_var_acc,
- const BoolFunctionPtr& evaluating_expr)
+ const BoolFunctionPtr& evaluating_expr,
+ bool may_cross)
: left_pos_expr_(left_pos_expr),
right_pos_expr_(right_pos_expr),
iter_var_acc_(iter_var_acc),
- evaluating_expr_(evaluating_expr)
+ evaluating_expr_(evaluating_expr),
+ may_cross(may_cross)
{
BOOST_ASSERT(left_pos_expr_);
BOOST_ASSERT(right_pos_expr_);
@@ -50,9 +53,10 @@ protected:
* iteration variable, evaluating positions within the
* range using supplied evaluation function.
* Range is trimmed to sentence boundaries.
- * In case of an invalid range (begin and end cross over or
- * either of them points Nowhere), False is returned and iteration
- * variable set to Nowhere.
+ * A range is invalid when begin or end point Nowhere. Depending on the
+ * value of may_cross, a range with begin following end is treated either
+ * as invalid (may_cross == False) or valid. In case of an invalid range,
+ * False is returned and iteration variable set to Nowhere.
* If range is correct, return value depends on stopping condition
* that describes how many positions within the range have to evaluate
* to true. Exact details depend on type of iteration, and are
diff --git a/libwccl/ops/functions/bool/iterations/atleast.h b/libwccl/ops/functions/bool/iterations/atleast.h
index 21d55360cb88f6686897ad9e553cf49bfc311569..a2b756eee5034dcc7fea5666762293fc7b856a1b 100644
--- a/libwccl/ops/functions/bool/iterations/atleast.h
+++ b/libwccl/ops/functions/bool/iterations/atleast.h
@@ -19,7 +19,8 @@ public:
const VariableAccessor<Position>& iter_var_acc,
const BoolFunctionPtr& evaluating_expr,
int min_matches)
- : Iteration(left_pos_expr, right_pos_expr, iter_var_acc, evaluating_expr),
+ : Iteration(left_pos_expr, right_pos_expr, iter_var_acc,
+ evaluating_expr, false), // false==no crossing ranges
min_matches_(min_matches)
{
BOOST_ASSERT(min_matches_ > 0);
diff --git a/libwccl/ops/functions/bool/iterations/leftlook.h b/libwccl/ops/functions/bool/iterations/leftlook.h
index 618aa3d11e63eefcfc9d3ed74abba08e5e9432a1..e0776c68c47a8f83e887795ab293f20f95c035ae 100644
--- a/libwccl/ops/functions/bool/iterations/leftlook.h
+++ b/libwccl/ops/functions/bool/iterations/leftlook.h
@@ -18,7 +18,8 @@ public:
const PosFunctionPtr& right_pos_expr,
const VariableAccessor<Position>& iter_var_acc,
const BoolFunctionPtr& evaluating_expr)
- : Iteration(left_pos_expr, right_pos_expr, iter_var_acc, evaluating_expr)
+ : Iteration(left_pos_expr, right_pos_expr, iter_var_acc,
+ evaluating_expr, false) // false==no crossing ranges
{
}
diff --git a/libwccl/ops/functions/bool/iterations/only.h b/libwccl/ops/functions/bool/iterations/only.h
index dce58cba7dcf366487b80057fa120c22bfc98651..f11d6f536836597834cf9c062fa124826e7e4d73 100644
--- a/libwccl/ops/functions/bool/iterations/only.h
+++ b/libwccl/ops/functions/bool/iterations/only.h
@@ -8,7 +8,8 @@ namespace Wccl {
/**
* Iterative operator "only", which mandates that
* evaluating expression should evaluate to true
- * on all positions in range.
+ * on all positions in range OR the range should
+ * be empty.
*/
class Only : public Iteration
{
@@ -18,7 +19,8 @@ public:
const PosFunctionPtr& right_pos_expr,
const VariableAccessor<Position>& iter_var_acc,
const BoolFunctionPtr& evaluating_expr)
- : Iteration(left_pos_expr, right_pos_expr, iter_var_acc, evaluating_expr)
+ : Iteration(left_pos_expr, right_pos_expr, iter_var_acc,
+ evaluating_expr, true)
{
}
diff --git a/libwccl/ops/functions/bool/iterations/rightlook.h b/libwccl/ops/functions/bool/iterations/rightlook.h
index dcc5e5fa722ef007c0a14e3d583d165f40f32a85..579aea3bd594034668c7038c17530cedc314fae8 100644
--- a/libwccl/ops/functions/bool/iterations/rightlook.h
+++ b/libwccl/ops/functions/bool/iterations/rightlook.h
@@ -18,7 +18,8 @@ public:
const PosFunctionPtr& right_pos_expr,
const VariableAccessor<Position>& iter_var_acc,
const BoolFunctionPtr& evaluating_expr)
- : Iteration(left_pos_expr, right_pos_expr, iter_var_acc, evaluating_expr)
+ : Iteration(left_pos_expr, right_pos_expr, iter_var_acc,
+ evaluating_expr, false) // false==no crossing ranges
{
}
diff --git a/libwccl/sentencecontext.h b/libwccl/sentencecontext.h
index a857a3fc43b5558bad1f2cf7115a89a451072f75..6775ef8d6b3a7a5e72879a0976af4148ecc4c257 100644
--- a/libwccl/sentencecontext.h
+++ b/libwccl/sentencecontext.h
@@ -88,6 +88,7 @@ public:
* value for left position
* @param abs_right reference to int value that will hold absolute
* value for right position
+ * @param may_cross set to true if crossing begin and end is admissible
* @returns true if range is valid; in this case abs_left and abs_right
* are set to absolute positions values for left and right Position.
* False is returned otherwise; in this case abs_left and abs_right
@@ -97,7 +98,8 @@ public:
const Position& left,
const Position& right,
int& abs_left,
- int& abs_right) const;
+ int& abs_right,
+ bool may_cross = false) const;
/// Position setter
void set_position(int new_position) {
@@ -196,7 +198,8 @@ bool SentenceContext::validate_range(
const Position& left,
const Position& right,
int& abs_left,
- int& abs_right) const
+ int& abs_right,
+ bool may_cross) const
{
abs_left = get_abs_position(left);
@@ -216,9 +219,10 @@ bool SentenceContext::validate_range(
if (abs_right >= size()) {
abs_right = size() - 1;
}
+
// is range valid? this covers "crossed" range, an empty sentence,
// and range outside boundaries of sentence
- if (abs_left > abs_right) {
+ if (!may_cross && (abs_left > abs_right)) {
abs_left = Position::Nowhere;
abs_right = Position::Nowhere;
return false;