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I'm having a hard time understanding why the following equivalence produces two different results:

echom a:events == '*' 
echom string(a:events) == '*'

The first one returns 1 while the second one returns 0. Why is this so?

  • what is a:events? – Mass Jun 28 at 1:17
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In vim, string() does not mean cast or convert a value to a string. It means create a new string which can be eval'd back the original value:

eval(string(x)) ==# x

So assuming a:events is a sting with the literal value *, then string(a:events) is the literal value '*'. The string had 1 character, but now has 3 characters.

As another example,

echo 'hello'->string()->string()->string()

gives

'''''''hello'''''''

Casting strings in vim script

Explicitly casting to a string is not always needed (as opposed to some other languages) since numbers are automatically converted to/from strings when necessary. For example,

strlen(123) = 3

Although vim script does have a distinct number and string type, you generally don't need to keep track of it yourself. But if you do need it, there's are a couple of options:

1: Since the only issue with string() is when the type is already string, we can just check first.

let x = type(x) == v:t_string ? x : string(x)

2: Per the documentation %s performs the conversion to string like :echo

printf('%s', x)
| improve this answer | |
  • what would be the closest thing to 'cast to string' in vimscript? Or does that not really exist? – David542 Jun 28 at 1:31
  • using string() carefully :) please see my edit. – Mass Jun 28 at 1:48

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