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implemented arrow like operators
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Araq 2014-12-08 08:56:04 +01:00
commit 2804c0373c
2 changed files with 36 additions and 37 deletions
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50
doc/manual/syntax.txt
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@ -5,24 +5,21 @@ 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 10 different levels of precedence.
Binary operators have 11 different levels of precedence.
Relevant character
------------------
An operator symbol's *relevant character* is its first
character unless the first character is ``\`` and its length is greater than 1
then it is the second character.
This rule allows to escape operator symbols with ``\`` and keeps the operator's
precedence and associativity; this is useful for meta programming.
Associativity
-------------
Binary operators whose relevant character is ``^`` are right-associative, all
other binary operators are left-associative.
Binary operators whose first character is ``^`` or its last character
is ``>`` are right-associative, all other binary operators are left-associative.
Exception: The single "greater than" ``>`` operator is left-associative too.
Operators ending in ``>`` but longer than a single character are
called `arrow like`:idx:.
Precedence
----------
@ -30,7 +27,7 @@ Precedence
Unary operators always bind stronger than any binary
operator: ``$a + b`` is ``($a) + b`` and not ``$(a + b)``.
If an unary operator's relevant character is ``@`` it is a `sigil-like`:idx:
If an unary operator's first character is ``@`` it is a `sigil-like`:idx:
operator which binds stronger than a ``primarySuffix``: ``@x.abc`` is parsed
as ``(@x).abc`` whereas ``$x.abc`` is parsed as ``$(x.abc)``.
@ -38,25 +35,26 @@ as ``(@x).abc`` whereas ``$x.abc`` is parsed as ``$(x.abc)``.
For binary operators that are not keywords the precedence is determined by the
following rules:
If the operator ends with ``=`` and its relevant character is none of
If the operator ends with ``=`` and its first character is none of
``<``, ``>``, ``!``, ``=``, ``~``, ``?``, it is an *assignment operator* which
has the lowest precedence.
Otherwise precedence is determined by the relevant character.
Otherwise precedence is determined by the first character.
================ =============================================== ================== ===============
Precedence level Operators Relevant character Terminal symbol
Precedence level Operators First character Terminal symbol
================ =============================================== ================== ===============
9 (highest) ``$ ^`` OP9
8 ``* / div mod shl shr %`` ``* % \ /`` OP8
7 ``+ -`` ``+ ~ |`` OP7
6 ``&`` ``&`` OP6
5 ``..`` ``.`` OP5
4 ``== <= < >= > != in notin is isnot not of`` ``= < > !`` OP4
3 ``and`` OP3
2 ``or xor`` OP2
1 ``@ : ?`` OP1
0 (lowest) *assignment operator* (like ``+=``, ``*=``) OP0
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
================ =============================================== ================== ===============