Refactored out most of internal work for summarizing data opening
the door for generating charts from it. A model is introduced
to hold information needed for a summary, Histogram command is
an example of a partial usage. This is the beginning.
Removed implicit arithmetic traits on Value and Primitive to avoid
mixed types panics. The std operations traits can't fail and we
can't guarantee that. We can handle gracefully now since compute_values
was introduced after the parser changes four months ago. The handling
logic should be taken care of either explicitly or in compute_values.
The zero identity trait was also removed (and implementing this forced
us to also implement Add, Mult, etc)
Also: the `math` operations now remove in the output if a given column is not computable:
```
> ls | math sum
──────┬──────────
size │ 150.9 KB
──────┴──────────
```
* Refactor InputStream and affected commands.
First, making `values` private and leaning on the `Stream` implementation makes
consumes of `InputStream` less likely to have to change in the future, if we
change what an `InputStream` is internally.
Second, we're dropping `Option<InputStream>` as the input to pipelines,
internals, and externals. Instead, `InputStream.is_empty` can be used to check
for "emptiness". Empty streams are typically only ever used as the first input
to a pipeline.
* Add run_external internal command.
We want to push external commands closer to internal commands, eventually
eliminating the concept of "external" completely. This means we can consolidate
a couple of things:
- Variable evaluation (for example, `$it`, `$nu`, alias vars)
- Behaviour of whole stream vs per-item external execution
It should also make it easier for us to start introducing argument signatures
for external commands,
* Update run_external.rs
* Update run_external.rs
* Update run_external.rs
* Update run_external.rs
Co-authored-by: Jonathan Turner <jonathandturner@users.noreply.github.com>
This improves incremental build time when working on what was previously
the root package. For example, previously all plugins would be rebuilt
with a change to `src/commands/classified/external.rs`, but now only
`nu-cli` will have to be rebuilt (and anything that depends on it).
