Add size_hint to ops (not very useful)

mps-interpreter/src/lang/filter.rs

@@ -363,6 +363,18 @@ impl<P: MpsFilterPredicate + 'static> Iterator for MpsFilterStatement<P> {
             }
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        match &self.iterable {
+            VariableOrOp::Variable(s) => self.context.as_ref()
+                .and_then(|x| x.variables.get_opt(s))
+                .and_then(|x| match x {
+                MpsType::Op(op) => Some(op.size_hint()),
+                _ => None
+            }),
+            VariableOrOp::Op(op) => op.try_real_ref().map(|x| x.size_hint()).ok()
+        }.unwrap_or((0, None))
+    }
 }
 
 pub struct MpsFilterStatementFactory<

mps-interpreter/src/lang/filter_replace.rs

@@ -310,6 +310,18 @@ impl<P: MpsFilterPredicate + 'static> Iterator for MpsFilterReplaceStatement<P>
             None => None,
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        match &self.iterable {
+            VariableOrOp::Variable(s) => self.context.as_ref()
+                .and_then(|x| x.variables.get_opt(s))
+                .and_then(|x| match x {
+                MpsType::Op(op) => Some(op.size_hint()),
+                _ => None
+            }),
+            VariableOrOp::Op(op) => op.try_real_ref().map(|x| x.size_hint()).ok()
+        }.unwrap_or((0, None))
+    }
 }
 
 fn declare_or_replace_item(

mps-interpreter/src/lang/sorter.rs

@@ -101,6 +101,10 @@ impl<S: MpsSorter + 'static> Iterator for MpsSortStatement<S> {
         }
         self.item_cache.pop_front()
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.iterable.try_real_ref().map(|x| x.size_hint()).unwrap_or((0, None))
+    }
 }
 
 pub struct MpsSortStatementFactory<S: MpsSorter + 'static, F: MpsSorterFactory<S> + 'static> {

mps-interpreter/src/lang/vocabulary/comment.rs

@@ -49,6 +49,10 @@ impl Iterator for CommentStatement {
     fn next(&mut self) -> Option<Self::Item> {
         None
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (0, Some(0))
+    }
 }
 
 impl MpsOp for CommentStatement {

mps-interpreter/src/lang/vocabulary/empty.rs

@@ -36,6 +36,10 @@ impl Iterator for EmptyStatement {
     fn next(&mut self) -> Option<Self::Item> {
         None
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (0, Some(0))
+    }
 }
 
 impl MpsOp for EmptyStatement {

mps-interpreter/src/lang/vocabulary/files.rs

@@ -95,6 +95,10 @@ impl Iterator for FilesStatement {
             None => None,
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.file_iter.as_ref().map(|x| x.size_hint()).unwrap_or((0, None))
+    }
 }
 
 impl MpsOp for FilesStatement {

mps-interpreter/src/lang/vocabulary/repeat.rs

@@ -147,6 +147,15 @@ impl Iterator for RepeatStatement {
             }
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        if self.inner_done {
+            let len = (self.cache.len() * (self.repetitions + 1)) - self.cache_position;
+            (len, Some(len))
+        } else {
+            (0, None)
+        }
+    }
 }
 
 impl MpsOp for RepeatStatement {

mps-interpreter/src/lang/vocabulary/reset.rs

@@ -51,6 +51,10 @@ impl Iterator for ResetStatement {
         }
         None
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (0, Some(0))
+    }
 }
 
 impl MpsOp for ResetStatement {

mps-interpreter/src/lang/vocabulary/sql_init.rs

@@ -55,6 +55,10 @@ impl Iterator for SqlInitStatement {
             Err(e) => Some(Err(e)),
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (0, Some(0))
+    }
 }
 
 impl MpsOp for SqlInitStatement {

mps-interpreter/src/lang/vocabulary/sql_query.rs

@@ -108,6 +108,11 @@ impl Iterator for SqlStatement {
             }
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let len = self.rows.as_ref().map(|x| x.len());
+        (len.unwrap_or(0), len)
+    }
 }
 
 impl Display for SqlStatement {

mps-interpreter/src/lang/vocabulary/sql_simple_query.rs

@@ -170,6 +170,11 @@ impl Iterator for SimpleSqlStatement {
             }
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let len = self.rows.as_ref().map(|x| x.len());
+        (len.unwrap_or(0), len)
+    }
 }
 
 impl Display for SimpleSqlStatement {

mps-interpreter/src/lang/vocabulary/variable_assign.rs

@@ -120,6 +120,10 @@ impl Iterator for AssignStatement {
             }
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (0, Some(1))
+    }
 }
 
 impl MpsOp for AssignStatement {