forked from extern/nushell
153 lines
4.6 KiB
Rust
153 lines
4.6 KiB
Rust
use nu_engine::CallExt;
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use nu_protocol::ast::Call;
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use nu_protocol::engine::{Command, EngineState, Stack};
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use nu_protocol::{
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Category, Example, IntoInterruptiblePipelineData, PipelineData, PipelineIterator, ShellError,
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Signature, Span, SyntaxShape, Value,
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};
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#[derive(Clone)]
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pub struct Nth;
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impl Command for Nth {
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fn name(&self) -> &str {
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"nth"
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}
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fn signature(&self) -> Signature {
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Signature::build("nth")
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.rest("rest", SyntaxShape::Int, "the number of the row to return")
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.switch("skip", "Skip the rows instead of selecting them", Some('s'))
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.category(Category::Filters)
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}
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fn usage(&self) -> &str {
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"Return or skip only the selected rows."
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}
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fn examples(&self) -> Vec<Example> {
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vec![
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Example {
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example: "[sam,sarah,2,3,4,5] | nth 0 1 2",
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description: "Get the first, second, and third row",
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result: Some(Value::List {
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vals: vec![
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Value::test_string("sam"),
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Value::test_string("sarah"),
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Value::test_int(2),
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],
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span: Span::test_data(),
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}),
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},
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Example {
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example: "[0,1,2,3,4,5] | nth 0 1 2",
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description: "Get the first, second, and third row",
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result: Some(Value::List {
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vals: vec![Value::test_int(0), Value::test_int(1), Value::test_int(2)],
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span: Span::test_data(),
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}),
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},
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Example {
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example: "[0,1,2,3,4,5] | nth -s 0 1 2",
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description: "Skip the first, second, and third row",
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result: Some(Value::List {
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vals: vec![Value::test_int(3), Value::test_int(4), Value::test_int(5)],
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span: Span::test_data(),
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}),
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},
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Example {
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example: "[0,1,2,3,4,5] | nth 0 2 4",
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description: "Get the first, third, and fifth row",
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result: Some(Value::List {
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vals: vec![Value::test_int(0), Value::test_int(2), Value::test_int(4)],
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span: Span::test_data(),
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}),
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},
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Example {
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example: "[0,1,2,3,4,5] | nth 2 0 4",
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description: "Get the first, third, and fifth row",
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result: Some(Value::List {
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vals: vec![Value::test_int(0), Value::test_int(2), Value::test_int(4)],
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span: Span::test_data(),
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}),
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},
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]
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}
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fn run(
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&self,
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engine_state: &EngineState,
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stack: &mut Stack,
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call: &Call,
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input: PipelineData,
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) -> Result<PipelineData, ShellError> {
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let mut rows: Vec<usize> = call.rest(engine_state, stack, 0)?;
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rows.sort_unstable();
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let skip = call.has_flag("skip");
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let pipeline_iter: PipelineIterator = input.into_iter();
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Ok(NthIterator {
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input: pipeline_iter,
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rows,
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skip,
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current: 0,
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}
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.into_pipeline_data(engine_state.ctrlc.clone()))
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}
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}
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struct NthIterator {
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input: PipelineIterator,
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rows: Vec<usize>,
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skip: bool,
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current: usize,
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}
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impl Iterator for NthIterator {
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type Item = Value;
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fn next(&mut self) -> Option<Self::Item> {
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loop {
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if !self.skip {
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if let Some(row) = self.rows.get(0) {
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if self.current == *row {
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self.rows.remove(0);
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self.current += 1;
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return self.input.next();
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} else {
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self.current += 1;
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let _ = self.input.next();
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continue;
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}
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} else {
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return None;
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}
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} else if let Some(row) = self.rows.get(0) {
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if self.current == *row {
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self.rows.remove(0);
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self.current += 1;
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let _ = self.input.next();
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continue;
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} else {
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self.current += 1;
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return self.input.next();
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}
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} else {
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return self.input.next();
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}
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}
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_examples() {
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use crate::test_examples;
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test_examples(Nth {})
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}
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}
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