Vim Expression Syntax: Operator Precedence and Ternary/Falsy Operators

Expression syntax *expression-syntax* Expression syntax summary, from least to most significant: |expr1| expr2 expr2 ? expr1 : expr1 if-then-else |expr2| expr3 expr3 || expr3 ... logical OR |expr3| expr4 expr4 && expr4 ... logical AND |expr4| expr5 expr5 == expr5 equal expr5 != expr5 not equal expr5 > expr5 greater than expr5 >= expr5 greater than or equal expr5 < expr5 smaller than expr5 <= expr5 smaller than or equal expr5 =~ expr5 regexp matches expr5 !~ expr5 regexp doesn't match expr5 ==? expr5 equal, ignoring case expr5 ==# expr5 equal, match case etc. As above, append ? for ignoring case, # for matching case expr5 is expr5 same |List|, |Dictionary| or |Blob| instance expr5 isnot expr5 different |List|, |Dictionary| or |Blob| instance |expr5| expr6 expr6 + expr6 ... number addition, list or blob concatenation expr6 - expr6 ... number subtraction expr6 . expr6 ... string concatenation expr6 .. expr6 ... string concatenation |expr6| expr7 expr7 * expr7 ... number multiplication expr7 / expr7 ... number division expr7 % expr7 ... number modulo |expr7| expr8 ! expr7 logical NOT - expr7 unary minus + expr7 unary plus |expr8| expr9 expr8[expr1] byte of a String or item of a |List| expr8[expr1 : expr1] substring of a String or sublist of a |List| expr8.name entry in a |Dictionary| expr8(expr1, ...) function call with |Funcref| variable expr8->name(expr1, ...) |method| call |expr9| number number constant "string" string constant, backslash is special `'string'` string constant, ' is doubled [expr1, ...] |List| `{expr1: expr1, ...}` |Dictionary| #{key: expr1, ...} |Dictionary| &option option value (expr1) nested expression variable internal variable va{ria}ble internal variable with curly braces $VAR environment variable @r contents of register "r" function(expr1, ...) function call func{ti}on(expr1, ...) function call with curly braces `{args -> expr1}` lambda expression "..." indicates that the operations in this level can be concatenated. Example: > &nu || &list && &shell == "csh" All expressions within one level are parsed from left to right. Expression nesting is limited to 1000 levels deep (300 when build with MSVC) to avoid running out of stack and crashing. *E1169* ------------------------------------------------------------------------------ expr1 *expr1* *ternary* *falsy-operator* *??* *E109* The ternary operator: expr2 ? expr1 : expr1 The falsy operator: expr2 ?? expr1 Ternary operator ~ The expression before the '?' is evaluated to a number. If it evaluates to |TRUE|, the result is the value of the expression between the '?' and ':', otherwise the result is the value of the expression after the ':'. Example: > :echo lnum == 1 ? "top" : lnum Since the first expression is an "expr2", it cannot contain another ?:. The other two expressions can, thus allow for recursive use of ?:. Example: > :echo lnum == 1 ? "top" : lnum == 1000 ? "last" : lnum To keep this readable, using |line-continuation| is suggested: > :echo lnum == 1 :\ ? "top" :\ : lnum == 1000 :\ ? "last" :\ : lnum You should always put a space before the ':', otherwise it can be mistaken for use in a variable such as "a:1". Falsy operator ~ This is also known as the "null coalescing operator", but that's too complicated, thus we just call it the falsy operator. The expression before the '??' is evaluated. If it evaluates to |truthy|, this is used as the result. Otherwise the expression after the '??' is evaluated and used as the result. This is most useful to have a default value for an expression that may result in zero or empty: > echo theList ?? 'list is empty' echo GetName() ?? 'unknown' These are similar, but not equal: > expr2 ?? expr1 expr2 ? expr2 : expr1 In the second line "expr2" is evaluated twice. ------------------------------------------------------------------------------ expr2 and expr3 *expr2*

This section provides a summary of Vim's expression syntax, listing operators from least to most significant precedence. It covers various operators including if-then-else (ternary), logical OR, logical AND, comparison operators (equality, inequality, greater than, less than, regular expression matching), arithmetic operators, and string concatenation. It also details accessing elements within strings, lists, and dictionaries. The section explains number, string, list, and dictionary constants, options, variables, register contents, and function calls. Finally, it explains the ternary operator (expr2 ? expr1 : expr1) and the falsy operator (expr2 ?? expr1).