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Diffstat (limited to 'doc/tut1.rst')
| -rw-r--r-- | doc/tut1.rst | 32 |
1 files changed, 9 insertions, 23 deletions
diff --git a/doc/tut1.rst b/doc/tut1.rst index 9e6f1ab3c..f2251c463 100644 --- a/doc/tut1.rst +++ b/doc/tut1.rst @@ -41,7 +41,7 @@ Save this code to the file "greetings.nim". Now compile and run it:: nim compile --run greetings.nim -With the ``--run`` `switch <nimc.html#command-line-switches>`_ Nim +With the ``--run`` `switch <nimc.html#compiler-usage-command-line-switches>`_ Nim executes the file automatically after compilation. You can give your program command line arguments by appending them after the filename:: @@ -58,7 +58,7 @@ To compile a release version use:: By default the Nim compiler generates a large amount of runtime checks aiming for your debugging pleasure. With ``-d:release`` these checks are `turned off and optimizations are turned on -<nimc.html#compile-time-symbols>`_. +<nimc.html#compiler-usage-compile-time-symbols>`_. Though it should be pretty obvious what the program does, I will explain the syntax: statements which are not indented are executed when the program @@ -944,12 +944,8 @@ String variables are **mutable**, so appending to a string is possible, and quite efficient. Strings in Nim are both zero-terminated and have a length field. A string's length can be retrieved with the builtin ``len`` procedure; the length never counts the terminating zero. Accessing the -terminating zero is not an error and often leads to simpler code: - -.. code-block:: nim - if s[i] == 'a' and s[i+1] == 'b': - # no need to check whether ``i < len(s)``! - ... +terminating zero is an error, it only exists so that a Nim string can be converted +to a ``cstring`` without doing a copy. The assignment operator for strings copies the string. You can use the ``&`` operator to concatenate strings and ``add`` to append to a string. @@ -960,11 +956,7 @@ enforced. For example, when reading strings from binary files, they are merely a sequence of bytes. The index operation ``s[i]`` means the i-th *char* of ``s``, not the i-th *unichar*. -String variables are initialized with a special value, called ``nil``. However, -most string operations cannot deal with ``nil`` (leading to an exception being -raised) for performance reasons. It is best to use empty strings ``""`` -rather than ``nil`` as the *empty* value. But ``""`` often creates a string -object on the heap, so there is a trade-off to be made here. +A string variable is initialized with the empty string ``""``. Integers @@ -1032,7 +1024,7 @@ procs for these conversions. Type Conversion --------------- -Conversion between basic types is performed by using the +Conversion between numerical types is performed by using the type as a function: .. code-block:: nim @@ -1309,11 +1301,7 @@ Example: x: seq[int] # a reference to a sequence of integers x = @[1, 2, 3, 4, 5, 6] # the @ turns the array into a sequence allocated on the heap -Sequence variables are initialized with ``nil``. However, most sequence -operations cannot deal with ``nil`` (leading to an exception being -raised) for performance reasons. Thus one should use empty sequences ``@[]`` -rather than ``nil`` as the *empty* value. But ``@[]`` creates a sequence -object on the heap, so there is a trade-off to be made here. +Sequence variables are initialized with ``@[]``. The ``for`` statement can be used with one or two variables when used with a sequence. When you use the one variable form, the variable will hold the value @@ -1355,11 +1343,9 @@ type does not matter. .. code-block:: nim :test: "nim c $1" var - fruits: seq[string] # reference to a sequence of strings that is initialized with 'nil' + fruits: seq[string] # reference to a sequence of strings that is initialized with '@[]' capitals: array[3, string] # array of strings with a fixed size - fruits = @[] # creates an empty sequence on the heap that will be referenced by 'fruits' - capitals = ["New York", "London", "Berlin"] # array 'capitals' allows assignment of only three elements fruits.add("Banana") # sequence 'fruits' is dynamically expandable during runtime fruits.add("Mango") @@ -1691,7 +1677,7 @@ rules apply: write(stdout, x(3)) # no error: A.x is called write(stdout, x("")) # no error: B.x is called - proc x*(a: int): string = nil + proc x*(a: int): string = discard write(stdout, x(3)) # ambiguous: which `x` is to call? |