In the current implementation of Nix, this list would be allocated
over and over. Iirc pennae tried to optimize static list allocation,
but gained no significant performance improvement.
Yes, this function name is inconveniently long, but it is important
for the name to explicitly reference the function and not be mistaken
for the implicit string conversions, which only happen for a smaller
set of values.
There's no need to use `unsafeDiscardStringContext` since
ee7fe64c0a
(Nix 1.8).
Also the separator can't have a context since `builtins.split` would fail, so
we can assume it doesn't.
* lib/strings: optimise hasInfix function
* lib/strings: optimise hasInfix further using regex
* rstudio: call hasInfix with a string
* lib/strings: remove let from hasInfix
Co-authored-by: pennae <82953136+pennae@users.noreply.github.com>
Co-authored-by: pennae <82953136+pennae@users.noreply.github.com>
Adds some functions related to string similarity:
- lib.strings.commonPrefixLength
- lib.strings.commonSuffixLength
- lib.strings.levenshtein
- lib.strings.levenshteinAtMost
The current implementation of the concatStringsSep fallback references
concatStrings whcih is just a partial application of concatStringsSep,
forming a circular dependency. Although this will almost never be
encountered as (assuming the user does not explicitly trigger it):
1. the or operator will short circuit both in lazy and strict
evaluation
2. this can only occur in Nix versions prior to 1.10
which is not compatible with various nix operations as of 2.3.15
However it is still important if scopedImport is used or the builtins
have been overwritten. lib.foldl' is used instead of builtins.foldl'
as the foldl' primops was introduced in the same release as concatStringsSep.
When a list is passed to isStorePath this is most likely a mistake and
it is therefore better to just return false. There is one case where
this theoretically makes sense (if a list contains a single element for
which isStorePath elem), but since that case is also probably seldomly
intentional, it may save someone from debbuging unclear evaluation
errors.
Nix can perform static scope checking, but whenever code is inside
a `with` expression, the analysis breaks down, because it can't
know statically what's in the attribute set whose attributes were
brought into scope. In those cases, Nix has to assume that
everything works out.
Except it doesnt. Removing `with` from lib/ revealed an undefined
variable in an error message.
If that doesn't convince you that we're better off without `with`,
I can tell you that this PR results in a 3% evaluation performance
improvement because Nix can look up local variables by index.
This adds up with applications like the module system.
Furthermore, removing `with` makes the binding site of each
variable obvious, which helps with comprehension.
