Adding more math constants (and a small correction to the description of an existing one) (#9181)

Adding more float constants for when
https://github.com/rust-lang/rust/issues/103883 is accepted and merged.
And fixing a small conflation in the description of the Euler number.
Please take a look and let me know if I've missed or screwed up
anything.

crates/nu-command/src/math/egamma.rs

@@ -0,0 +1,64 @@
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Type, Value,
+};
+
+#[allow(clippy::excessive_precision)]
+/// The Euler-Mascheroni constant (γ)
+pub const EGAMMA: f64 = 0.577215664901532860606512090082402431_f64;
+
+#[derive(Clone)]
+pub struct SubCommand;
+
+impl Command for SubCommand {
+    fn name(&self) -> &str {
+        "math egamma"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("math egamma")
+            .input_output_types(vec![(Type::Any, Type::Float)])
+            .category(Category::Math)
+    }
+
+    fn usage(&self) -> &str {
+        "Returns the Euler–Mascheroni constant γ. ( 1 | math egamma)."
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["euler", "constant", "gamma"]
+    }
+
+    #[allow(clippy::approx_constant)]
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            example: "math egamma | math round --precision 3",
+            description: "Get the first three decimal digits of γ",
+            result: Some(Value::test_float(0.577)),
+        }]
+    }
+
+    fn run(
+        &self,
+        _engine_state: &EngineState,
+        _stack: &mut Stack,
+        call: &Call,
+        _input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        // TODO: replace with std::f64::consts::EGAMMA when available https://github.com/rust-lang/rust/issues/103883
+        Ok(Value::float(EGAMMA, call.head).into_pipeline_data())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(SubCommand {})
+    }
+}

crates/nu-command/src/math/euler.rs

@@ -23,7 +23,7 @@ impl Command for SubCommand {
     }
 
     fn search_terms(&self) -> Vec<&str> {
-        vec!["euler", "constant"]
+        vec!["euler", "number", "constant"]
     }
 
     #[allow(clippy::approx_constant)]

crates/nu-command/src/math/mod.rs

@@ -9,6 +9,7 @@ mod avg;
 mod ceil;
 mod cos;
 mod cosh;
+mod egamma;
 mod euler;
 mod exp;
 mod floor;
@@ -19,6 +20,7 @@ mod max;
 mod median;
 mod min;
 mod mode;
+mod phi;
 mod pi;
 mod product;
 mod reducers;
@@ -64,7 +66,9 @@ pub use arcsinh::SubCommand as MathArcSinH;
 pub use arctan::SubCommand as MathArcTan;
 pub use arctanh::SubCommand as MathArcTanH;
 
+pub use egamma::SubCommand as MathEulerGamma;
 pub use euler::SubCommand as MathEuler;
+pub use phi::SubCommand as MathPhi;
 pub use pi::SubCommand as MathPi;
 pub use tau::SubCommand as MathTau;
 

crates/nu-command/src/math/phi.rs

@@ -0,0 +1,64 @@
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Type, Value,
+};
+
+#[allow(clippy::excessive_precision)]
+/// The golden ratio (φ)
+pub const PHI: f64 = 1.618033988749894848204586834365638118_f64;
+
+#[derive(Clone)]
+pub struct SubCommand;
+
+impl Command for SubCommand {
+    fn name(&self) -> &str {
+        "math phi"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("math phi")
+            .input_output_types(vec![(Type::Any, Type::Float)])
+            .category(Category::Math)
+    }
+
+    fn usage(&self) -> &str {
+        "Returns the golden ratio φ. ( (1 + sqrt(5) ) / 2 )"
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["golden", "ratio", "constant"]
+    }
+
+    #[allow(clippy::approx_constant)]
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            example: "math phi | math round --precision 3",
+            description: "Get the first two decimal digits of φ",
+            result: Some(Value::test_float(1.618)),
+        }]
+    }
+
+    fn run(
+        &self,
+        _engine_state: &EngineState,
+        _stack: &mut Stack,
+        call: &Call,
+        _input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        // TODO: replace with std::f64::consts::PHI when available https://github.com/rust-lang/rust/issues/103883
+        Ok(Value::float(PHI, call.head).into_pipeline_data())
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(SubCommand {})
+    }
+}