Make mode subcommand: math mode (#2043)

* Update calculate to return a table when Value is a table

* impl mode subcommand for math

* add tests for math mode subcommand

* add table/row tests for math mode subcommand

* fix formatting

crates/nu-cli/src/cli.rs

@@ -351,6 +351,7 @@ pub fn create_default_context(
             whole_stream_command(MathAverage),
             whole_stream_command(MathMedian),
             whole_stream_command(MathMinimum),
+            whole_stream_command(MathMode),
             whole_stream_command(MathMaximum),
             whole_stream_command(MathSummation),
             // File format output

crates/nu-cli/src/commands.rs

@@ -198,7 +198,9 @@ pub(crate) use lines::Lines;
 pub(crate) use ls::Ls;
 #[allow(unused_imports)]
 pub(crate) use map_max_by::MapMaxBy;
-pub(crate) use math::{Math, MathAverage, MathMaximum, MathMedian, MathMinimum, MathSummation};
+pub(crate) use math::{
+    Math, MathAverage, MathMaximum, MathMedian, MathMinimum, MathMode, MathSummation,
+};
 pub(crate) use merge::Merge;
 pub(crate) use mkdir::Mkdir;
 pub(crate) use mv::Move;

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

@@ -35,11 +35,11 @@ impl WholeStreamCommand for Command {
 mod tests {
     use super::*;
     use crate::commands::math::{
-        avg::average, max::maximum, median::median, min::minimum, sum::summation, utils::calculate,
-        utils::MathFunction,
+        avg::average, max::maximum, median::median, min::minimum, mode::mode, sum::summation,
+        utils::calculate, utils::MathFunction,
     };
     use nu_plugin::row;
-    use nu_plugin::test_helpers::value::{decimal, int};
+    use nu_plugin::test_helpers::value::{decimal, int, table};
     use nu_protocol::Value;
 
     #[test]
@@ -74,6 +74,7 @@ mod tests {
                     Ok(int(10)),
                     Ok(int(10)),
                     Ok(int(10)),
+                    Ok(table(&vec![int(10)])),
                     Ok(int(10)),
                 ],
             },
@@ -86,6 +87,7 @@ mod tests {
                     Ok(int(10)),
                     Ok(int(30)),
                     Ok(int(20)),
+                    Ok(table(&vec![int(10), int(20), int(30)])),
                     Ok(int(60)),
                 ],
             },
@@ -98,6 +100,7 @@ mod tests {
                     Ok(int(10)),
                     Ok(decimal(26.5)),
                     Ok(decimal(26.5)),
+                    Ok(table(&vec![decimal(26.5)])),
                     Ok(decimal(63)),
                 ],
             },
@@ -110,6 +113,7 @@ mod tests {
                     Ok(int(-14)),
                     Ok(int(10)),
                     Ok(int(-11)),
+                    Ok(table(&vec![int(-14), int(-11), int(10)])),
                     Ok(int(-15)),
                 ],
             },
@@ -122,6 +126,7 @@ mod tests {
                     Ok(decimal(-13.5)),
                     Ok(int(10)),
                     Ok(decimal(-11.5)),
+                    Ok(table(&vec![decimal(-13.5), decimal(-11.5), int(10)])),
                     Ok(decimal(-15)),
                 ],
             },
@@ -139,6 +144,10 @@ mod tests {
                     Ok(row!["col1".to_owned() => int(1), "col2".to_owned() => int(5)]),
                     Ok(row!["col1".to_owned() => int(4), "col2".to_owned() => int(8)]),
                     Ok(row!["col1".to_owned() => decimal(2.5), "col2".to_owned() => decimal(6.5)]),
+                    Ok(row![
+                        "col1".to_owned() => table(&vec![int(1), int(2), int(3), int(4)]),
+                        "col2".to_owned() => table(&vec![int(5), int(6), int(7), int(8)])
+                    ]),
                     Ok(row!["col1".to_owned() => int(10), "col2".to_owned() => int(26)]),
                 ],
             },
@@ -154,8 +163,7 @@ mod tests {
         for tc in tt.iter() {
             let tc: &TestCase = tc; // Just for type annotations
             let math_functions: Vec<MathFunction> =
-                vec![average, minimum, maximum, median, summation];
-
+                vec![average, minimum, maximum, median, mode, summation];
             let results = math_functions
                 .into_iter()
                 .map(|mf| calculate(&tc.values, &test_tag, mf))

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

@@ -3,6 +3,7 @@ pub mod command;
 pub mod max;
 pub mod median;
 pub mod min;
+pub mod mode;
 pub mod sum;
 pub mod utils;
 
@@ -11,4 +12,5 @@ pub use command::Command as Math;
 pub use max::SubCommand as MathMaximum;
 pub use median::SubCommand as MathMedian;
 pub use min::SubCommand as MathMinimum;
+pub use mode::SubCommand as MathMode;
 pub use sum::SubCommand as MathSummation;

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

@@ -0,0 +1,94 @@
+use crate::commands::math::utils::run_with_function;
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use nu_errors::ShellError;
+use nu_protocol::{Signature, UntaggedValue, Value};
+use std::cmp::Ordering;
+
+pub struct SubCommand;
+
+#[async_trait]
+impl WholeStreamCommand for SubCommand {
+    fn name(&self) -> &str {
+        "math mode"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("math mode")
+    }
+
+    fn usage(&self) -> &str {
+        "Gets the most frequent element(s) from a list of numbers or tables"
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        run_with_function(
+            RunnableContext {
+                input: args.input,
+                registry: registry.clone(),
+                shell_manager: args.shell_manager,
+                host: args.host,
+                ctrl_c: args.ctrl_c,
+                current_errors: args.current_errors,
+                name: args.call_info.name_tag,
+                raw_input: args.raw_input,
+            },
+            mode,
+        )
+        .await
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Get the mode(s) of a list of numbers",
+            example: "echo [3 3 9 12 12 15] | math mode",
+            result: Some(vec![
+                UntaggedValue::int(3).into_untagged_value(),
+                UntaggedValue::int(12).into_untagged_value(),
+            ]),
+        }]
+    }
+}
+
+pub fn mode(values: &[Value], name: &Tag) -> Result<Value, ShellError> {
+    let mut frequency_map = std::collections::HashMap::new();
+    for v in values {
+        let counter = frequency_map.entry(v.value.clone()).or_insert(0);
+        *counter += 1;
+    }
+
+    let mut max_freq = -1;
+    let mut modes = Vec::<Value>::new();
+    for (value, frequency) in frequency_map.iter() {
+        match max_freq.cmp(&frequency) {
+            Ordering::Less => {
+                max_freq = *frequency;
+                modes.clear();
+                modes.push(value.clone().into_value(name));
+            }
+            Ordering::Equal => {
+                modes.push(value.clone().into_value(name));
+            }
+            Ordering::Greater => (),
+        }
+    }
+
+    crate::commands::sort_by::sort(&mut modes, &[], name)?;
+    Ok(UntaggedValue::Table(modes).into_value(name))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::SubCommand;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(SubCommand {})
+    }
+}

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

@@ -15,7 +15,17 @@ pub async fn run_with_function(
     let values: Vec<Value> = input.drain_vec().await;
     let res = calculate(&values, &name, mf);
     match res {
-        Ok(v) => Ok(OutputStream::one(ReturnSuccess::value(v))),
+        Ok(v) => {
+            if v.value.is_table() {
+                Ok(OutputStream::from(
+                    v.table_entries()
+                        .map(|v| ReturnSuccess::value(v.clone()))
+                        .collect::<Vec<_>>(),
+                ))
+            } else {
+                Ok(OutputStream::one(ReturnSuccess::value(v)))
+            }
+        }
         Err(e) => Err(e),
     }
 }