Add arbitrary base math log

crates/nu-command/src/default_context.rs

@@ -421,6 +421,7 @@ pub fn create_default_context() -> EngineState {
  MathPi,
  MathEuler,
  MathLn,
+ MathLog,
  };
 
  // Network

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

@@ -0,0 +1,134 @@
+use nu_engine::CallExt;
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{
+ Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Type, Value,
+};
+
+#[derive(Clone)]
+pub struct SubCommand;
+
+impl Command for SubCommand {
+ fn name(&self) -> &str {
+ "math log"
+ }
+
+ fn signature(&self) -> Signature {
+ Signature::build("math log")
+ .required(
+ "base",
+ SyntaxShape::Number,
+ "Base for which the logarithm should be computed",
+ )
+ .input_output_types(vec![(Type::Number, Type::Float)])
+ .vectorizes_over_list(true)
+ .category(Category::Math)
+ }
+
+ fn usage(&self) -> &str {
+ "Returns the logarithm for an arbitrary base."
+ }
+
+ fn search_terms(&self) -> Vec<&str> {
+ vec!["base", "exponent", "inverse", "euler"]
+ }
+
+ fn run(
+ &self,
+ engine_state: &EngineState,
+ stack: &mut Stack,
+ call: &Call,
+ input: PipelineData,
+ ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
+ let head = call.head;
+ let base: Spanned<f64> = call.req(engine_state, stack, 0)?;
+
+ if base.item <= 0.0f64 {
+ return Err(ShellError::UnsupportedInput(
+ "Base has to be greater 0".into(),
+ base.span,
+ ));
+ }
+
+ let base = base.item;
+ input.map(
+ move |value| operate(value, head, base),
+ engine_state.ctrlc.clone(),
+ )
+ }
+
+ fn examples(&self) -> Vec<Example> {
+ vec![
+ Example {
+ description: "Get the logarithm of 100 to the base 10",
+ example: "100 | math log 10",
+ result: Some(Value::test_float(2.0f64)),
+ },
+ Example {
+ example: "[16 8 4] | math log 2",
+ description: "Get the log2 of a list of values",
+ result: Some(Value::List {
+ vals: vec![
+ Value::test_float(4.0),
+ Value::test_float(3.0),
+ Value::test_float(2.0),
+ ],
+ span: Span::test_data(),
+ }),
+ },
+ ]
+ }
+}
+
+fn operate(value: Value, head: Span, base: f64) -> Value {
+ match value {
+ numeric @ (Value::Int { .. } | Value::Float { .. }) => {
+ let (val, span) = match numeric {
+ Value::Int { val, span } => (val as f64, span),
+ Value::Float { val, span } => (val, span),
+ _ => unreachable!(),
+ };
+
+ if val <= 0.0 {
+ return Value::Error {
+ error: ShellError::UnsupportedInput(
+ "'math log' undefined for values outside the open interval (0, Inf)."
+ .into(),
+ span,
+ ),
+ };
+ }
+ // Specialize for better precision/performance
+ let val = if base == 10.0 {
+ val.log10()
+ } else if base == 2.0 {
+ val.log2()
+ } else {
+ val.log(base)
+ };
+
+ Value::Float { val, span }
+ }
+ other => Value::Error {
+ error: ShellError::UnsupportedInput(
+ format!(
+ "Only numerical values are supported, input type: {:?}",
+ other.get_type()
+ ),
+ other.span().unwrap_or(head),
+ ),
+ },
+ }
+}
+
+#[cfg(test)]
+mod test {
+ use super::*;
+
+ #[test]
+ fn test_examples() {
+ use crate::test_examples;
+
+ test_examples(SubCommand {})
+ }
+}

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

@@ -13,6 +13,7 @@ mod euler;
 mod eval;
 mod floor;
 mod ln;
+mod log;
 pub mod math_;
 mod max;
 mod median;
@@ -66,4 +67,5 @@ pub use arctanh::SubCommand as MathArcTanH;
 pub use euler::SubCommand as MathEuler;
 pub use pi::SubCommand as MathPi;
 
+pub use self::log::SubCommand as MathLog;
 pub use ln::SubCommand as MathLn;