mirror of
https://github.com/nushell/nushell
synced 2024-12-30 23:08:56 +00:00
25a8caa9b0
* WIP: experiment with simpler expressions * fix simple invoke * update tests * fix a few tests * Make paren parsing more robust * fix external args * Remove old invocation * Update tests * Update tests
3.4 KiB
3.4 KiB
empty?
Check for empty values. Pass the column names to check emptiness. Optionally pass a block as the last parameter if setting contents to empty columns is wanted.
Examples
Check if a value is empty
> echo '' | empty?
true
Given the following meals
> echo [[meal size]; [arepa small] [taco '']]
═══╦═══════╦═══════
# ║ meal ║ size
═══╬═══════╬═══════
0 ║ arepa ║ small
1 ║ taco ║
═══╩═══════╩═══════
Show the empty contents
> echo [[meal size]; [arepa small] [taco '']] | empty? meal size
═══╦═══════╦═══════
# ║ meal ║ size
═══╬═══════╬═══════
0 ║ false ║ false
1 ║ false ║ true
═══╩═══════╩═══════
Let's assume we have a report of totals per day. For simplicity we show just for three days 2020/04/16, 2020/07/10, and 2020/11/16. Like so
> echo [[2020/04/16 2020/07/10 2020/11/16]; ['' 27 37]]
═══╦════════════╦════════════╦════════════
# ║ 2020/04/16 ║ 2020/07/10 ║ 2020/11/16
═══╬════════════╬════════════╬════════════
0 ║ ║ 27 ║ 37
═══╩════════════╩════════════╩════════════
In the future, the report now has many totals logged per day. In this example, we have 1 total for the day 2020/07/10 and 2020/11/16 like so
> echo [[2020/04/16 2020/07/10 2020/11/16]; ['' [27] [37]]]
═══╦════════════╦════════════════╦════════════════
# ║ 2020/04/16 ║ 2020/07/10 ║ 2020/11/16
═══╬════════════╬════════════════╬════════════════
0 ║ ║ [table 1 rows] ║ [table 1 rows]
═══╩════════════╩════════════════╩════════════════
We want to add two totals (numbers 33 and 37) for the day 2020/04/16
Set a table with two numbers for the empty column
> echo [[2020/04/16 2020/07/10 2020/11/16]; ['' [27] [37]]] | empty? 2020/04/16 { [33 37] }
═══╦════════════════╦════════════════╦════════════════
# ║ 2020/04/16 ║ 2020/07/10 ║ 2020/11/16
═══╬════════════════╬════════════════╬════════════════
0 ║ [table 2 rows] ║ [table 1 rows] ║ [table 1 rows]
═══╩════════════════╩════════════════╩════════════════
Checking all the numbers
> echo [[2020/04/16 2020/07/10 2020/11/16]; ['' [27] [37]]] | empty? 2020/04/16 { [33 37] } | pivot _ totals | get totals
═══╦════
0 ║ 33
1 ║ 37
2 ║ 27
3 ║ 37
═══╩════