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Diffstat (limited to 'doc/tut1.rst')
| -rw-r--r-- | doc/tut1.rst | 38 |
1 files changed, 26 insertions, 12 deletions
diff --git a/doc/tut1.rst b/doc/tut1.rst index 6d54d88a3..24874096c 100644 --- a/doc/tut1.rst +++ b/doc/tut1.rst @@ -395,20 +395,29 @@ Since counting up occurs so often in programs, Nim also has a `.. <system.html#...i,T,T>`_ iterator that does the same: .. code-block:: nim - for i in 1..10: + for i in 1 .. 10: ... -Zero-indexed counting have two shortcuts ``..<`` and ``..^`` to simplify counting to one less than the higher index: +Zero-indexed counting has two shortcuts ``..<`` and ``.. ^1`` +(`backwards index operator <system.html#^.t%2Cint>`_) to simplify +counting to one less than the higher index: .. code-block:: nim - for i in 0..<10: - ... # 0..9 + for i in 0 ..< 10: + ... # 0 .. 9 or .. code-block:: nim var s = "some string" - for i in 0..<s.len: + for i in 0 ..< s.len: + ... + +or + +.. code-block:: nim + var s = "some string" + for idx, c in s[0 .. ^1]: ... Other useful iterators for collections (like arrays and sequences) are @@ -1402,8 +1411,8 @@ define operators which accept Slice objects to define ranges. a = "Nim is a programming language" b = "Slices are useless." - echo a[7..12] # --> 'a prog' - b[11..^2] = "useful" + echo a[7 .. 12] # --> 'a prog' + b[11 .. ^2] = "useful" echo b # --> 'Slices are useful.' In the previous example slices are used to modify a part of a string. The @@ -1425,17 +1434,22 @@ indices are 0 11 17 using indices ^19 ^8 ^2 using ^ syntax -where ``b[0..^1]`` is equivalent to ``b[0..b.len-1]`` and ``b[0..<b.len]``, and it -can be seen that the ``^1`` provides a short-hand way of specifying the ``b.len-1``. +where ``b[0 .. ^1]`` is equivalent to ``b[0 .. b.len-1]`` and ``b[0 ..< b.len]``, and it +can be seen that the ``^1`` provides a short-hand way of specifying the ``b.len-1``. See +the `backwards index operator <system.html#^.t%2Cint>`_. In the above example, because the string ends in a period, to get the portion of the string that is "useless" and replace it with "useful". -``b[11..^2]`` is the portion "useless", and ``b[11..^2] = "useful"`` replaces the +``b[11 .. ^2]`` is the portion "useless", and ``b[11 .. ^2] = "useful"`` replaces the "useless" portion with "useful", giving the result "Slices are useful." -Note: alternate ways of writing this are ``b[^8..^2] = "useful"`` or -as ``b[11..b.len-2] = "useful"`` or as ``b[11..<b.len-1] = "useful"``. +Note 1: alternate ways of writing this are ``b[^8 .. ^2] = "useful"`` or +as ``b[11 .. b.len-2] = "useful"`` or as ``b[11 ..< b.len-1] = "useful"``. + +Note 2: As the ``^`` template returns a `distinct int <manual.html#types-distinct-type>`_ +of type ``BackwardsIndex``, we can have a ``lastIndex`` constant defined as ``const lastIndex = ^1``, +and later used as ``b[0 .. lastIndex]``. Objects ------- |