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Diffstat (limited to 'doc/manual/syntax.txt')
| -rw-r--r-- | doc/manual/syntax.txt | 42 |
1 files changed, 25 insertions, 17 deletions
diff --git a/doc/manual/syntax.txt b/doc/manual/syntax.txt index cf44eb588..c444a3995 100644 --- a/doc/manual/syntax.txt +++ b/doc/manual/syntax.txt @@ -15,17 +15,22 @@ Associativity Binary operators whose first character is ``^`` are right-associative, all other binary operators are left-associative. -Operators ending in ``>`` but longer than a single character are -called `arrow like`:idx:. - +.. 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 +Unary operators always bind stronger than any binary operator: ``$a + b`` is ``($a) + b`` and not ``$(a + b)``. -If an unary operator's first character is ``@`` it is a `sigil-like`:idx: +If an unary operator's first character is ``@`` it is a `sigil-like`:idx: operator which binds stronger than a ``primarySuffix``: ``@x.abc`` is parsed as ``(@x).abc`` whereas ``$x.abc`` is parsed as ``$(x.abc)``. @@ -33,9 +38,12 @@ as ``(@x).abc`` whereas ``$x.abc`` is parsed as ``$(x.abc)``. For binary operators that are not keywords the precedence is determined by the following rules: -If the operator ends with ``=`` and its first character is none of +Operators ending in either ``->``, ``~>`` or ``=>`` are called +`arrow like`:idx:, and have the lowest precedence of all operators. + +If the operator ends with ``=`` and its first character is none of ``<``, ``>``, ``!``, ``=``, ``~``, ``?``, it is an *assignment operator* which -has the lowest precedence. +has the second lowest precedence. Otherwise precedence is determined by the first character. @@ -43,14 +51,14 @@ Otherwise precedence is determined by the first character. Precedence level Operators First character Terminal symbol ================ =============================================== ================== =============== 10 (highest) ``$ ^`` OP10 - 9 ``* / div mod shl shr %`` ``* % \ /`` OP9 - 8 ``+ -`` ``+ ~ |`` OP8 + 9 ``* / div mod shl shr %`` ``* % \ /`` OP9 + 8 ``+ -`` ``+ - ~ |`` OP8 7 ``&`` ``&`` OP7 6 ``..`` ``.`` OP6 - 5 ``== <= < >= > != in notin is isnot not of`` ``= < > !`` OP5 + 5 ``== <= < >= > != in notin is isnot not of`` ``= < > !`` OP5 4 ``and`` OP4 3 ``or xor`` OP3 - 2 ``@ : ?`` OP2 + 2 ``@ : ?`` OP2 1 *assignment operator* (like ``+=``, ``*=``) OP1 0 (lowest) *arrow like operator* (like ``->``, ``=>``) OP0 ================ =============================================== ================== =============== @@ -60,14 +68,14 @@ Strong spaces ------------- The number of spaces preceding a non-keyword operator affects precedence -if the experimental parser directive ``#!strongSpaces`` is used. Indentation +if the experimental parser directive ``#?strongSpaces`` is used. Indentation is not used to determine the number of spaces. If 2 or more operators have the same number of preceding spaces the precedence table applies, so ``1 + 3 * 4`` is still parsed as ``1 + (3 * 4)``, but ``1+3 * 4`` is parsed as ``(1+3) * 4``: .. code-block:: nim - #! strongSpaces - if foo+4 * 4 == 8 and b&c | 9 ++ + #? strongSpaces + if foo+4 * 4 == 8 and b&c | 9 ++ bar: echo "" # is parsed as @@ -75,10 +83,10 @@ is still parsed as ``1 + (3 * 4)``, but ``1+3 * 4`` is parsed as ``(1+3) * 4``: Furthermore whether an operator is used a prefix operator is affected by the -number of spaces: +number of spaces: .. code-block:: nim - #! strongSpaces + #? strongSpaces echo $foo # is parsed as echo($foo) @@ -87,7 +95,7 @@ This also affects whether ``[]``, ``{}``, ``()`` are parsed as constructors or as accessors: .. code-block:: nim - #! strongSpaces + #? strongSpaces echo (1,2) # is parsed as echo((1,2)) |