diff options
| author | itchyny <itchyny@cybozu.co.jp> | 2023-07-09 12:56:59 +0900 |
|---|---|---|
| committer | Nico Williams <nico@cryptonector.com> | 2023-07-08 23:13:15 -0500 |
| commit | d8072564c28d38d29aa0a7c416621f02c19f7f44 (patch) | |
| tree | 47e98bb8a510f15d927b3e0ea50d292881e009d9 | |
| parent | e2bc8de8bb0487e9ae9f8d8203cf4988154ba3f0 (diff) | |
Fix nth/2 to emit empty on index out of range
| -rw-r--r-- | docs/content/manual/manual.yml | 6 | ||||
| -rw-r--r-- | src/builtin.jq | 4 | ||||
| -rw-r--r-- | tests/jq.test | 8 |
3 files changed, 11 insertions, 7 deletions
diff --git a/docs/content/manual/manual.yml b/docs/content/manual/manual.yml index 30b0cf60..183e4a5d 100644 --- a/docs/content/manual/manual.yml +++ b/docs/content/manual/manual.yml @@ -2832,10 +2832,8 @@ sections: The `first(expr)` and `last(expr)` functions extract the first and last values from `expr`, respectively. - The `nth(n; expr)` function extracts the nth value output by - `expr`. This can be defined as `def nth(n; expr): - last(limit(n + 1; expr));`. Note that `nth(n; expr)` doesn't - support negative values of `n`. + The `nth(n; expr)` function extracts the nth value output by `expr`. + Note that `nth(n; expr)` doesn't support negative values of `n`. examples: - program: '[first(range(.)), last(range(.)), nth(./2; range(.))]' diff --git a/src/builtin.jq b/src/builtin.jq index aac22cb7..146a64a3 100644 --- a/src/builtin.jq +++ b/src/builtin.jq @@ -163,7 +163,9 @@ def any(condition): any(.[]; condition); def all: all(.[]; .); def any: any(.[]; .); def last(g): reduce g as $item (null; $item); -def nth($n; g): if $n < 0 then error("nth doesn't support negative indices") else last(limit($n + 1; g)) end; +def nth($n; g): + if $n < 0 then error("nth doesn't support negative indices") + else label $out | foreach g as $item ($n + 1; . - 1; if . <= 0 then $item, break $out else empty end) end; def first: .[0]; def last: .[-1]; def nth($n): .[$n]; diff --git a/tests/jq.test b/tests/jq.test index 193025da..4e693452 100644 --- a/tests/jq.test +++ b/tests/jq.test @@ -319,9 +319,13 @@ null "badness" [1] -[first(range(.)), last(range(.)), nth(0; range(.)), nth(5; range(.)), try nth(-1; range(.)) catch .] +[first(range(.)), last(range(.))] 10 -[0,9,0,5,"nth doesn't support negative indices"] +[0,9] + +[nth(0,5,9,10,15; range(.)), try nth(-1; range(.)) catch .] +10 +[0,5,9,"nth doesn't support negative indices"] # Check that first(g) does not extract more than one value from g first(1,error("foo")) |