Document builtins.substring negative length behavior (#9226)

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Silvan Mosberger 2023-10-24 11:22:02 +02:00 committed by GitHub
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@ -3720,10 +3720,11 @@ static RegisterPrimOp primop_substring({
.doc = R"(
Return the substring of *s* from character position *start*
(zero-based) up to but not including *start + len*. If *start* is
greater than the length of the string, an empty string is returned,
and if *start + len* lies beyond the end of the string, only the
substring up to the end of the string is returned. *start* must be
non-negative. For example,
greater than the length of the string, an empty string is returned.
If *start + len* lies beyond the end of the string or *len* is `-1`,
only the substring up to the end of the string is returned.
*start* must be non-negative.
For example,
```nix
builtins.substring 0 3 "nixos"