# HG changeset patch
# User Peter Kovacs <kpeter@inf.elte.hu>
# Date 1518907472 -3600
# Node ID 4fd76139b69ec938db4d67ce0927ad5923647ed2
# Parent  1f4f01870c1e20fd9ea3c999805f0de2c161c772
Add operator[] to Path structures (#250)

diff -r 1f4f01870c1e -r 4fd76139b69e lemon/path.h
--- a/lemon/path.h	Sat Feb 17 23:44:15 2018 +0100
+++ b/lemon/path.h	Sat Feb 17 23:44:32 2018 +0100
@@ -182,6 +182,15 @@
       return ArcIt(*this, n);
     }
 
+    /// \brief The n-th arc.
+    ///
+    /// Gives back the n-th arc. This operator is just an alias for \ref nth(),
+    /// it runs in O(1) time.
+    /// \pre \c n is in the range <tt>[0..length() - 1]</tt>.
+    const Arc& operator[](int n) const {
+      return nth(n);
+    }
+
     /// \brief The first arc of the path
     const Arc& front() const {
       return head.empty() ? tail.front() : head.back();
@@ -402,6 +411,15 @@
       return ArcIt(*this, n);
     }
 
+    /// \brief The n-th arc.
+    ///
+    /// Gives back the n-th arc. This operator is just an alias for \ref nth(),
+    /// it runs in O(1) time.
+    /// \pre \c n is in the range <tt>[0..length() - 1]</tt>.
+    const Arc& operator[](int n) const {
+      return data[n];
+    }
+
     /// \brief The first arc of the path.
     const Arc& front() const {
       return data.front();
@@ -618,6 +636,15 @@
       return ArcIt(*this, node);
     }
 
+    /// \brief The n-th arc.
+    ///
+    /// Looks for the n-th arc in O(n) time. This operator is just an alias
+    /// for \ref nth().
+    /// \pre \c n is in the range <tt>[0..length() - 1]</tt>.
+    const Arc& operator[](int n) const {
+      return nth(n);
+    }
+
     /// \brief Length of the path.
     int length() const {
       int len = 0;
@@ -966,6 +993,15 @@
       return ArcIt(*this, n);
     }
 
+    /// \brief The n-th arc.
+    ///
+    /// Gives back the n-th arc. This operator is just an alias for \ref nth(),
+    /// it runs in O(1) time.
+    /// \pre \c n is in the range <tt>[0..length() - 1]</tt>.
+    const Arc& operator[](int n) const {
+      return _arcs[n];
+    }
+
     /// \brief The length of the path.
     int length() const { return len; }
 
diff -r 1f4f01870c1e -r 4fd76139b69e test/path_test.cc
--- a/test/path_test.cc	Sat Feb 17 23:44:15 2018 +0100
+++ b/test/path_test.cc	Sat Feb 17 23:44:32 2018 +0100
@@ -108,6 +108,11 @@
     checkBackAndFrontInsertablePath<ListPath<GR> >();
     checkBackInsertablePath<SimplePath<GR> >();
 
+    checkSubscriptOperator<Path<GR> >();
+    checkSubscriptOperator<SimplePath<GR> >();
+    checkSubscriptOperator<StaticPath<GR> >();
+    checkSubscriptOperator<ListPath<GR> >();
+
     checkListPathSplitAndSplice();
   }
 
@@ -273,6 +278,25 @@
     check(checkPath(cgr, cp), "Wrong checkPath()");
   }
 
+  template <typename P>
+  void checkSubscriptOperator() {
+    SimplePath<GR> p0;
+    p0.addBack(a1);
+    p0.addBack(a3);
+    p0.addBack(a2);
+    P p = p0;
+    check(!p.empty(), "Wrong empty()");
+    check(p.length() == 3, "Wrong length");
+    check(p.front() == a1, "Wrong front()");
+    check(p.back() == a2, "Wrong back()");
+    check(p.nth(0) == a1, "Wrong nth()");
+    check(p.nth(1) == a3, "Wrong nth()");
+    check(p.nth(2) == a2, "Wrong nth()");
+    check(p[0] == a1, "Wrong operator[]");
+    check(p[1] == a3, "Wrong operator[]");
+    check(p[2] == a2, "Wrong operator[]");
+  }
+
   void checkListPathSplitAndSplice() {
 
     // Build a path with spliceFront() and spliceBack()