Add to `doc/limitations.md` about `nil?` redefinition; ref 4996709 [ci skip]
KOBAYASHI Shuji
4 years ago
| 125 | 125 | true |
| 126 | 126 | ``` |
| 127 | 127 | |
| 128 | ## defined? | |
| 128 | ## `defined?` | |
| 129 | 129 | |
| 130 | 130 | The `defined?` keyword is considered too complex to be fully |
| 131 | 131 | implemented. It is recommended to use `const_defined?` and |
| 185 | 185 | ` 'ab' ` |
| 186 | 186 | Behavior of the operator wasn't changed. |
| 187 | 187 | |
| 188 | ## Kernel#binding is not supported | |
| 188 | ## `Kernel#binding` is not supported | |
| 189 | 189 | |
| 190 | 190 | `Kernel#binding` method is not supported. |
| 191 | 191 | |
| 237 | 237 | from the default expression of optional arguments and keyword arguments, |
| 238 | 238 | since actual assignment is done after the evaluation of those default |
| 239 | 239 | expressions. Thus: |
| 240 | ||
| 240 | ||
| 241 | 241 | ```ruby |
| 242 | 242 | def f(a,(b,c),d=b) |
| 243 | 243 | p [a,b,c,d] |
| 246 | 246 | ``` |
| 247 | 247 | |
| 248 | 248 | CRuby gives `[1,2,3,nil]`. mruby raises `NoMethodError` for `b`. |
| 249 | ||
| 250 | ## `nil?` redefinition in conditional expressions | |
| 251 | ||
| 252 | Redefinition of `nil?` is ignored in conditional expressions. | |
| 253 | ||
| 254 | ```ruby | |
| 255 | a = "a" | |
| 256 | def a.nil? | |
| 257 | true | |
| 258 | end | |
| 259 | puts(a.nil? ? "truthy" : "falsy") | |
| 260 | ``` | |
| 261 | ||
| 262 | Ruby outputs `falsy`. mruby outputs `truthy`. | |