new command fmt to format numbers (#707)

* new command `fmt` to format numbers

* remove comments

crates/nu-command/src/conversions/fmt.rs

@@ -0,0 +1,176 @@
+use nu_engine::CallExt;
+use nu_protocol::{
+    ast::{Call, CellPath},
+    engine::{Command, EngineState, Stack},
+    Category, Example, PipelineData, ShellError, Signature, Span, Value,
+};
+
+#[derive(Clone)]
+pub struct Fmt;
+
+impl Command for Fmt {
+    fn name(&self) -> &str {
+        "fmt"
+    }
+
+    fn usage(&self) -> &str {
+        "format numbers"
+    }
+
+    fn signature(&self) -> nu_protocol::Signature {
+        Signature::build("fmt").category(Category::Conversions)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "format numbers",
+            example: "42 | fmt",
+            result: Some(Value::Record {
+                cols: vec![
+                    "binary".into(),
+                    "debug".into(),
+                    "display".into(),
+                    "lowerexp".into(),
+                    "lowerhex".into(),
+                    "octal".into(),
+                    "upperexp".into(),
+                    "upperhex".into(),
+                ],
+                vals: vec![
+                    Value::String {
+                        val: "0b101010".to_string(),
+                        span: Span::test_data(),
+                    },
+                    Value::String {
+                        val: "42".to_string(),
+                        span: Span::test_data(),
+                    },
+                    Value::String {
+                        val: "42".to_string(),
+                        span: Span::test_data(),
+                    },
+                    Value::String {
+                        val: "4.2e1".to_string(),
+                        span: Span::test_data(),
+                    },
+                    Value::String {
+                        val: "0x2a".to_string(),
+                        span: Span::test_data(),
+                    },
+                    Value::String {
+                        val: "0o52".to_string(),
+                        span: Span::test_data(),
+                    },
+                    Value::String {
+                        val: "4.2E1".to_string(),
+                        span: Span::test_data(),
+                    },
+                    Value::String {
+                        val: "0x2A".to_string(),
+                        span: Span::test_data(),
+                    },
+                ],
+                span: Span::test_data(),
+            }),
+        }]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
+        fmt(engine_state, stack, call, input)
+    }
+}
+
+fn fmt(
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+    input: PipelineData,
+) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
+    let head = call.head;
+    let column_paths: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
+
+    input.map(
+        move |v| {
+            if column_paths.is_empty() {
+                action(&v, head)
+            } else {
+                let mut ret = v;
+                for path in &column_paths {
+                    let r =
+                        ret.update_cell_path(&path.members, Box::new(move |old| action(old, head)));
+                    if let Err(error) = r {
+                        return Value::Error { error };
+                    }
+                }
+
+                ret
+            }
+        },
+        engine_state.ctrlc.clone(),
+    )
+}
+
+pub fn action(input: &Value, span: Span) -> Value {
+    match input {
+        Value::Int { val, .. } => fmt_it(*val, span),
+        Value::Filesize { val, .. } => fmt_it(*val, span),
+        _ => Value::Error {
+            error: ShellError::UnsupportedInput(
+                format!("unsupported input type: {:?}", input.get_type()),
+                span,
+            ),
+        },
+    }
+}
+
+fn fmt_it(num: i64, span: Span) -> Value {
+    let mut cols = vec![];
+    let mut vals = vec![];
+
+    cols.push("binary".into());
+    vals.push(Value::string(format!("{:#b}", num), span));
+
+    cols.push("debug".into());
+    vals.push(Value::string(format!("{:#?}", num), span));
+
+    cols.push("display".into());
+    vals.push(Value::string(format!("{}", num), span));
+
+    cols.push("lowerexp".into());
+    vals.push(Value::string(format!("{:#e}", num), span));
+
+    cols.push("lowerhex".into());
+    vals.push(Value::string(format!("{:#x}", num), span));
+
+    cols.push("octal".into());
+    vals.push(Value::string(format!("{:#o}", num), span));
+
+    // cols.push("pointer".into());
+    // vals.push(Value::string(format!("{:#p}", &num), span));
+
+    cols.push("upperexp".into());
+    vals.push(Value::string(format!("{:#E}", num), span));
+
+    cols.push("upperhex".into());
+    vals.push(Value::string(format!("{:#X}", num), span));
+
+    Value::Record { cols, vals, span }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(Fmt {})
+    }
+}

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

@@ -1,3 +1,5 @@
+mod fmt;
 pub(crate) mod into;
 
+pub use fmt::Fmt;
 pub use into::*;

crates/nu-command/src/default_context.rs

@@ -241,6 +241,7 @@ pub fn create_default_context(cwd: impl AsRef<Path>) -> EngineState {
             IntoFilesize,
             IntoInt,
             IntoString,
+            Fmt,
         };
 
         // Env