Files
nushell/crates/nu-command/src/dataframe/expressions/alias.rs
Fernando Herrera 8bd68416e3 Lazy dataframes (#5546)
* lazyframe definition

* expressions and lazy frames

* new alias expression

* more expression commands

* updated to polars main

* more expressions and groupby

* more expressions, fetch and sort-by

* csv reader

* removed open csv

* unique function

* joining functions

* join lazy frames commands with eager commands

* corrected tests

* Update .gitignore

* Update .gitignore

Co-authored-by: JT <547158+jntrnr@users.noreply.github.com>
2022-05-16 08:27:43 +01:00

58 lines
1.4 KiB
Rust

use super::super::values::NuExpression;
use nu_engine::CallExt;
use nu_protocol::{
ast::Call,
engine::{Command, EngineState, Stack},
Category, Example, PipelineData, ShellError, Signature, SyntaxShape,
};
#[derive(Clone)]
pub struct ExprAlias;
impl Command for ExprAlias {
fn name(&self) -> &str {
"dfr as"
}
fn usage(&self) -> &str {
"Creates an alias expression"
}
fn signature(&self) -> Signature {
Signature::build(self.name())
.required(
"Alias name",
SyntaxShape::String,
"Alias name for the expression",
)
.category(Category::Custom("expressions".into()))
}
fn examples(&self) -> Vec<Example> {
vec![Example {
description: "Creates and alias expression",
example: "(dfr col a | df as new_a)",
result: None,
}]
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let alias: String = call.req(engine_state, stack, 0)?;
let expr = NuExpression::try_from_pipeline(input, call.head)?;
let expr: NuExpression = expr.into_polars().alias(alias.as_str()).into();
Ok(PipelineData::Value(
NuExpression::into_value(expr, call.head),
None,
))
}
}