r - 在 R 中创建一元运算符

Question

是否可以在 R 中创建一元运算符？我知道可以像这样创建二元运算符:

setGeneric("%power%", function(x, y) x ^ y)
2 %power% 4

但是是否可以创建像-这样的一元运算符。我试过类似的东西:

setGeneric("%-%", function(x) -x)
%-% 3

但是没用

Answer 1

R 解析器不支持自定义一元运算符。

R language definition 中支持的运算符列表的副本:

-   Minus, can be unary or binary
+   Plus, can be unary or binary
!   Unary not
~   Tilde, used for model formulae, can be either unary or binary
?   Help
:   Sequence, binary (in model formulae: interaction)
*   Multiplication, binary
/   Division, binary
^   Exponentiation, binary
%x% Special binary operators, x can be replaced by any valid name
%%  Modulus, binary
%/% Integer divide, binary
%*% Matrix product, binary
%o% Outer product, binary
%x% Kronecker product, binary
%in%    Matching operator, binary (in model formulae: nesting)
<   Less than, binary
>   Greater than, binary
==  Equal to, binary
>=  Greater than or equal to, binary
<=  Less than or equal to, binary
&   And, binary, vectorized
&&  And, binary, not vectorized
|   Or, binary, vectorized
||  Or, binary, not vectorized
<-  Left assignment, binary
->  Right assignment, binary
$   List subset, binary

(解析器还支持二元运算符 :=，此处未记录，因为 base R 未使用它。)

请注意，唯一的自定义运算符(“%x% 特殊二元运算符，x 可以替换为任何有效名称”)是二进制的。

因此，您唯一的选择是重载现有的一元运算符，分别为它编写一个方法。