Vim Expression Comparison Details: Lists, Dictionaries, Funcrefs, and String/Number Comparisons

evaluates to 0 "abc" ==? "Abc" evaluates to 1 "abc" == "Abc" evaluates to 1 if 'ignorecase' is set, 0 otherwise *E691* *E692* A |List| can only be compared with a |List| and only "equal", "not equal", "is" and "isnot" can be used. This compares the values of the list, recursively. Ignoring case means case is ignored when comparing item values. *E735* *E736* A |Dictionary| can only be compared with a |Dictionary| and only "equal", "not equal", "is" and "isnot" can be used. This compares the key/values of the |Dictionary| recursively. Ignoring case means case is ignored when comparing item values. *E694* A |Funcref| can only be compared with a |Funcref| and only "equal", "not equal", "is" and "isnot" can be used. Case is never ignored. Whether arguments or a Dictionary are bound (with a partial) matters. The Dictionaries must also be equal (or the same, in case of "is") and the arguments must be equal (or the same). To compare Funcrefs to see if they refer to the same function, ignoring bound Dictionary and arguments, use |get()| to get the function name: > if get(Part1, 'name') == get(Part2, 'name') " Part1 and Part2 refer to the same function Using "is" or "isnot" with a |List|, |Dictionary| or |Blob| checks whether the expressions are referring to the same |List|, |Dictionary| or |Blob| instance. A copy of a |List| is different from the original |List|. When using "is" without a |List|, |Dictionary| or |Blob|, it is equivalent to using "equal", using "isnot" is equivalent to using "not equal". Except that a different type means the values are different: > echo 4 == '4' 1 echo 4 is '4' 0 echo 0 is [] 0 "is#"/"isnot#" and "is?"/"isnot?" can be used to match and ignore case. When comparing a String with a Number, the String is converted to a Number, and the comparison is done on Numbers. This means that: > echo 0 == 'x' 1 because 'x' converted to a Number is zero. However: > echo [0] == ['x'] 0 Inside a List or Dictionary this conversion is not used. When comparing two Strings, this is done with strcmp() or stricmp(). This results in the mathematical difference (comparing byte values), not necessarily the alphabetical difference in the local language. When using the operators with a trailing '#', or the short version and 'ignorecase' is off, the comparing is done with strcmp(): case matters. When using the operators with a trailing '?', or the short version and 'ignorecase' is set, the comparing is done with stricmp(): case is ignored. 'smartcase' is not used. The "=~" and "!~" operators match the lefthand argument with the righthand argument, which is used as a pattern. See |pattern| for what a pattern is. This matching is always done like 'magic' was set and 'cpoptions' is empty, no matter what the actual value of 'magic' or 'cpoptions' is. This makes scripts portable. To avoid backslashes in the regexp pattern to be doubled, use a single-quote string, see |literal-string|. Since a string is considered to be a single line, a multi-line pattern (containing \n, backslash-n) will not match. However, a literal NL character can be matched like an ordinary character. Examples: "foo\nbar" =~ "\n" evaluates to 1 "foo\nbar" =~ "\\n" evaluates to 0 ------------------------------------------------------------------------------ expr5 and expr6 *expr5* *expr6* expr6 + expr6 Number addition, |List| or |Blob| concatenation *expr-+* expr6 - expr6 Number subtraction *expr--* expr6 . expr6 String concatenation *expr-.* expr6 .. expr6 String concatenation *expr-..* For |Lists| only "+" is possible and then both expr6 must be a list. The result is a new list with the two lists Concatenated. For String concatenation ".." is preferred, since "." is ambiguous, it is also used for |Dict| member access and floating point numbers. expr7 * expr7 Number multiplication *expr-star* expr7 / expr7 Number division *expr-/* expr7 % expr7 Number modulo

This section delves into specific comparison scenarios in Vim expressions, particularly when using lists, dictionaries, and funcrefs. It details the limitations and behaviors of the `equal`, `not equal`, `is`, and `isnot` operators when applied to these data types. It also clarifies how Vim handles comparisons between strings and numbers, including case sensitivity controlled by 'ignorecase' and the use of `strcmp()` and `stricmp()`. The section further explains the `=~` and `!~` operators for pattern matching and concludes with a brief overview of arithmetic and string concatenation operators.