FEATURE: Add a trait for tracking lines and columns in text.

src/combinators.rs

@@ -759,3 +759,12 @@ macro_rules! make_fn {
     };
 
 }
+
+#[macro_export]
+macro_rules! pos {
+    ($i:expr) => {{
+        let _i = $i.clone();
+        use $crate::TextPositionTracker;
+        $crate::Result::Complete($i, (_i.line(), _i.column()))
+    }}
+}

src/iter.rs

@@ -2,7 +2,7 @@
 use std::fmt::Debug;
 use std::iter::Iterator;
 
-use super::{InputIter, Offsetable, Span, SpanRange};
+use super::{InputIter, Offsetable, Span, SpanRange, TextPositionTracker};
 
 /// Implements `InputIter` for any slice of T.
 #[derive(Debug)]
@@ -86,6 +86,8 @@ impl<'a, T: Debug> From<&'a Vec<T>> for SliceIter<'a, T> {
 pub struct StrIter<'a> {
     source: &'a str,
     offset: usize,
+    line: usize,
+    column: usize,
 }
 
 impl<'a> StrIter<'a> {
@@ -94,6 +96,8 @@ impl<'a> StrIter<'a> {
         StrIter {
             source: source,
             offset: 0,
+            line: 1,
+            column: 1,
         }
     }
 }
@@ -103,8 +107,15 @@ impl<'a> Iterator for StrIter<'a> {
 
     fn next(&mut self) -> Option<Self::Item> {
         match self.source.as_bytes().get(self.offset) {
+            // TODO count lines and columns.
             Some(item) => {
                 self.offset += 1;
+                if *item == b'\n' {
+                    self.line += 1;
+                    self.column = 1;
+                } else {
+                    self.column += 1;
+                }
                 Some(item)
             }
             None => None,
@@ -118,11 +129,23 @@ impl<'a> Offsetable for StrIter<'a> {
     }
 }
 
+impl<'a> TextPositionTracker for StrIter<'a> {
+    fn line(&self) -> usize {
+        self.line
+    }
+
+    fn column(&self) -> usize {
+        self.column
+    }
+}
+
 impl<'a> Clone for StrIter<'a> {
     fn clone(&self) -> Self {
         StrIter {
             source: self.source,
             offset: self.offset,
+            line: self.line,
+            column: self.column,
         }
     }
 }

src/lib.rs

@@ -61,6 +61,12 @@ impl Offsetable for usize {
     }
 }
 
+/// Trait for Inputs that can track lines and columns in a text input.
+pub trait TextPositionTracker {
+    fn line(&self) -> usize;
+    fn column(&self) -> usize;
+}
+
 pub enum SpanRange {
     Range(std::ops::Range<usize>),
     RangeTo(std::ops::RangeTo<usize>),

src/test.rs

@@ -462,3 +462,21 @@ fn test_ascii_ws_carriage_return() {
     let result = ascii_ws(iter);
     assert!(result.is_complete());
 }
+
+use super::TextPositionTracker;
+#[test]
+fn test_position_tracking_striter() {
+    let input_str = "\n";
+    let mut iter = StrIter::new(input_str);
+    assert_eq!(iter.line(), 1);
+    assert_eq!(iter.column(), 1);
+    iter.next();
+    assert_eq!(iter.line(), 2);
+    assert_eq!(iter.column(), 1);
+    let pos_result = pos!(iter);
+    assert!(pos_result.is_complete());
+    if let Result::Complete(_, (line, column)) = pos_result {
+        assert_eq!(line, 2);
+        assert_eq!(column, 1);
+    }
+}