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| -rw-r--r-- | doc/tut1.rst | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/doc/tut1.rst b/doc/tut1.rst index 65906376e..06ee84c0d 100644 --- a/doc/tut1.rst +++ b/doc/tut1.rst @@ -407,7 +407,7 @@ or ... Other useful iterators for collections (like arrays and sequences) are -* ``items`` and ``mitems``, which provides immutable and mutable elements respectively, and +* ``items`` and ``mitems``, which provides immutable and mutable elements respectively, and * ``pairs`` and ``mpairs`` which provides the element and an index number (immutable and mutable respectively) .. code-block:: nim @@ -1394,6 +1394,27 @@ slice's bounds can hold any value supported by their type, but it is the proc using the slice object which defines what values are accepted. + To understand some of the different ways of specifying the indices of strings, arrays, sequences, etc., + it must be remembered that Nim uses zero-based indices. + + So the string ``b`` is of length 19, and two different ways of specifying the indices are + + .. code-block:: nim + + "Slices are useless." + | | | + 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`` + + 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 "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"`` or as .... Tuples ------ |