Added math abs command. (#2789)

crates/nu-cli/src/cli.rs

@@ -217,6 +217,7 @@ pub fn create_default_context(interactive: bool) -> Result<EvaluationContext, Bo
             whole_stream_command(AutoenvTrust),
             whole_stream_command(AutoenvUnTrust),
             whole_stream_command(Math),
+            whole_stream_command(MathAbs),
             whole_stream_command(MathAverage),
             whole_stream_command(MathEval),
             whole_stream_command(MathMedian),

crates/nu-cli/src/commands.rs

@@ -212,8 +212,8 @@ pub(crate) use last::Last;
 pub(crate) use lines::Lines;
 pub(crate) use ls::Ls;
 pub(crate) use math::{
-    Math, MathAverage, MathCeil, MathEval, MathFloor, MathMaximum, MathMedian, MathMinimum,
-    MathMode, MathProduct, MathRound, MathStddev, MathSummation, MathVariance,
+    Math, MathAbs, MathAverage, MathCeil, MathEval, MathFloor, MathMaximum, MathMedian,
+    MathMinimum, MathMode, MathProduct, MathRound, MathStddev, MathSummation, MathVariance,
 };
 pub(crate) use merge::Merge;
 pub(crate) use mkdir::Mkdir;

crates/nu-cli/src/commands/math/abs.rs

@@ -0,0 +1,73 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{Primitive, Signature, UntaggedValue, Value};
+
+pub struct SubCommand;
+
+#[async_trait]
+impl WholeStreamCommand for SubCommand {
+    fn name(&self) -> &str {
+        "math abs"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("math abs")
+    }
+
+    fn usage(&self) -> &str {
+        "Returns absolute values of a list of numbers"
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        _: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        let mapped = args.input.map(move |val| match val.value {
+            UntaggedValue::Primitive(Primitive::Int(val)) => {
+                UntaggedValue::int(val.magnitude().clone()).into()
+            }
+            UntaggedValue::Primitive(Primitive::Decimal(val)) => {
+                UntaggedValue::decimal(val.abs()).into()
+            }
+            UntaggedValue::Primitive(Primitive::Duration(val)) => {
+                UntaggedValue::duration(val.magnitude().clone()).into()
+            }
+            other => abs_default(other),
+        });
+        Ok(OutputStream::from_input(mapped))
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Get absolute of each value in a list of numbers",
+            example: "echo [-50 -100.0 25] | math abs",
+            result: Some(vec![
+                UntaggedValue::int(50).into(),
+                UntaggedValue::decimal_from_float(100.0, Span::default()).into(),
+                UntaggedValue::int(25).into(),
+            ]),
+        }]
+    }
+}
+
+fn abs_default(_: UntaggedValue) -> Value {
+    UntaggedValue::Error(ShellError::unexpected(
+        "Only numerical values are supported",
+    ))
+    .into()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::ShellError;
+    use super::SubCommand;
+
+    #[test]
+    fn examples_work_as_expected() -> Result<(), ShellError> {
+        use crate::examples::test as test_examples;
+
+        Ok(test_examples(SubCommand {})?)
+    }
+}

crates/nu-cli/src/commands/math/mod.rs

@@ -1,3 +1,4 @@
+pub mod abs;
 pub mod avg;
 pub mod ceil;
 pub mod command;
@@ -16,6 +17,7 @@ pub mod variance;
 mod reducers;
 mod utils;
 
+pub use abs::SubCommand as MathAbs;
 pub use avg::SubCommand as MathAverage;
 pub use ceil::SubCommand as MathCeil;
 pub use command::Command as Math;

crates/nu-protocol/src/value.rs

@@ -242,8 +242,8 @@ impl UntaggedValue {
     }
 
     /// Helper for creating date duration values
-    pub fn duration(nanos: BigInt) -> UntaggedValue {
-        UntaggedValue::Primitive(Primitive::Duration(nanos))
+    pub fn duration(nanos: impl Into<BigInt>) -> UntaggedValue {
+        UntaggedValue::Primitive(Primitive::Duration(nanos.into()))
     }
 
     /// Helper for creating datatime values

docs/commands/math.md

@@ -3,6 +3,7 @@
 Mathematical functions that generally only operate on a list of numbers (integers, decimals, bytes) and tables.
 Currently the following functions are implemented:
 
+* `math abs`: Returns absolute values of a list of numbers
 * `math avg`: Finds the average of a list of numbers or tables
 * `math ceil`: Applies the ceil function to a list of numbers
 * [`math eval`](math-eval.md): Evaluates a list of math expressions into numbers
@@ -147,6 +148,15 @@ To get the average of the file sizes in a directory, simply pipe the size column
 ───┴────
 ```
 
+```shell
+> echo [1 -2 -3.0] | math abs
+───┬────────
+ 0 │      1
+ 1 │      2
+ 2 │ 3.0000
+───┴────────
+```
+
 ### Dates
 
 ```shell