1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
Syntax
======
This section lists Nim's standard syntax. How the parser handles
the indentation is already described in the `Lexical Analysis`_ section.
Nim allows user-definable operators.
Binary operators have 11 different levels of precedence.
Associativity
-------------
Binary operators whose first character is ``^`` are right-associative, all
other binary operators are left-associative.
.. code-block:: nim
proc `^/`(x, y: float): float =
# a right-associative division operator
result = x / y
echo 12 ^/ 4 ^/ 8 # 24.0 (4 / 8 = 0.5, then 12 / 0.5 = 24.0)
echo 12 / 4 / 8 # 0.375 (12 / 4 = 3.0, then 3 / 8 = 0.375)
Precedence
----------
Unary operators always bind stronger than any binary
operator: ``$a + b`` is ``($a) + b`` and not ``$(a + b)``.
If an unary operator's first character is ``@`` it is a `sigil-like`:idx:
operator which binds stronger than a ``primarySuffix``: ``@x.abc`` is parsed
as ``(@x).abc`` whereas ``$x.abc`` is parsed as ``$(x.abc)``.
For binary operators that are not keywords the precedence is determined by the
following rules:
Operators ending in either ``->``, ``~>`` or ``=>`` are called
`arrow like`:idx:, and have the lowest precedence of all operators.
If the operator ends with ``=`` and its first character is none of
``<``, ``>``, ``!``, ``=``, ``~``, ``?``, it is an *assignment operator* which
has the second lowest precedence.
Otherwise precedence is determined by the first character.
================ =============================================== ================== ===============
Precedence level Operators First character Terminal symbol
================ =============================================== ================== ===============
10 (highest) ``$ ^`` OP10
9 ``* / div mod shl shr %`` ``* % \ /`` OP9
8 ``+ -`` ``+ - ~ |`` OP8
7 ``&`` ``&`` OP7
6 ``..`` ``.`` OP6
5 ``== <= < >= > != in notin is isnot not of`` ``= < > !`` OP5
4 ``and`` OP4
3 ``or xor`` OP3
2 ``@ : ?`` OP2
1 *assignment operator* (like ``+=``, ``*=``) OP1
0 (lowest) *arrow like operator* (like ``->``, ``=>``) OP0
================ =============================================== ================== ===============
Whether an operator is used a prefix operator is also affected by preceeding whitespace (this parsing change was introduced with version 0.13.0):
.. code-block:: nim
echo $foo
# is parsed as
echo($foo)
Grammar
-------
The grammar's start symbol is ``module``.
.. include:: ../grammar.txt
:literal:
|