Brett Stahlman wrote:
> The following expression
>
> var>10?var:10
>
> generates the following errors:
>
> E121: Undefined variable: var:10
> E15: Invalid expression: var>10?var:10
>
> The reason is that find_name_end uses eval_isnamec unconditionally to
> decide whether a character is a valid variable name character,
> with the result that `:' is always gobbled up as part of the variable
> name, even if it's not the second character in the name string
> (ie, even if it doesn't separate the scope prefix from the variable
> name). find_var_ht, on the other hand, will not permit a colon
> anywhere but at character index 1 in the variable name; hence, E121,
> and ultimately, E15.
>
> Since `:' is part of a valid VimL operator, and is not valid anywhere
> other than at index 1 in a non-curly-brace variable name,
> there is no ambiguity in the expression shown above. For expressions such as
>
> b>10?b:a
>
> the ambiguity would be resolved according to the relative precedence
> of the ternary operator and the variable scope separator (`:'). I
> would assume that the precedence of the scope operator would be higher
> (since Vim treats it as part of 'variable', whose
> precedence is much higher than that of the ternary operator); hence,
> in the preceding example, the expression would be evaluated as
>
> (b>10) ? (b:a)
>
> which would indeed be a syntax error...
>
> Should eval_isnamec (or perhaps its caller) take into consideration
> the character index when deciding whether `:' is to be
> considered part of the variable name?
The docs clearly state:
You should always put a space before the ':', otherwise it can
be mistaken for use in a variable such as "a:1".
In some cases var:10 can be recognized as not being a variable name, but
this leads to undetected mistakes and makes it difficult to add more
scopes later.
It's a good habit to put spaces around ? and : anyway. Unless you never
read back what you've written perhaps.
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