forked from extern/nushell
118 lines
3.4 KiB
Rust
118 lines
3.4 KiB
Rust
use nu_engine::CallExt;
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use nu_protocol::ast::Call;
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use nu_protocol::engine::{Command, EngineState, Stack};
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use nu_protocol::{
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Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Value,
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};
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#[derive(Clone)]
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pub struct SubCommand;
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impl Command for SubCommand {
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fn name(&self) -> &str {
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"math eval"
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}
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fn usage(&self) -> &str {
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"Evaluate a math expression into a number"
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}
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fn signature(&self) -> Signature {
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Signature::build("math eval").optional(
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"math expression",
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SyntaxShape::String,
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"the math expression to evaluate",
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)
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}
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fn run(
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&self,
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engine_state: &EngineState,
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stack: &mut Stack,
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call: &Call,
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input: PipelineData,
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) -> Result<PipelineData, ShellError> {
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let spanned_expr: Option<Spanned<String>> = call.opt(engine_state, stack, 0)?;
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eval(spanned_expr, input, engine_state)
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}
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fn examples(&self) -> Vec<Example> {
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vec![Example {
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description: "Evalulate math in the pipeline",
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example: "'10 / 4' | math eval",
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result: Some(Value::Float {
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val: 2.5,
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span: Span::unknown(),
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}),
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}]
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}
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}
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pub fn eval(
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spanned_expr: Option<Spanned<String>>,
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input: PipelineData,
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engine_state: &EngineState,
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) -> Result<PipelineData, ShellError> {
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if let Some(expr) = spanned_expr {
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match parse(&expr.item, &expr.span) {
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Ok(value) => Ok(PipelineData::Value(value)),
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Err(err) => Err(ShellError::UnsupportedInput(
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format!("Math evaluation error: {}", err),
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expr.span,
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)),
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}
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} else {
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if let PipelineData::Value(Value::Nothing { .. }) = input {
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return Ok(input);
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}
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input.map(
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move |val| {
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if let Ok(string) = val.as_string() {
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match parse(&string, &val.span().unwrap_or_else(|_| Span::unknown())) {
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Ok(value) => value,
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Err(err) => Value::Error {
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error: ShellError::UnsupportedInput(
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format!("Math evaluation error: {}", err),
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val.span().unwrap_or_else(|_| Span::unknown()),
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),
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},
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}
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} else {
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Value::Error {
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error: ShellError::UnsupportedInput(
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"Expected a string from pipeline".to_string(),
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val.span().unwrap_or_else(|_| Span::unknown()),
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),
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}
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}
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},
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engine_state.ctrlc.clone(),
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)
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}
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}
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pub fn parse(math_expression: &str, span: &Span) -> Result<Value, String> {
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let mut ctx = meval::Context::new();
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ctx.var("tau", std::f64::consts::TAU);
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match meval::eval_str_with_context(math_expression, &ctx) {
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Ok(num) if num.is_infinite() || num.is_nan() => Err("cannot represent result".to_string()),
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Ok(num) => Ok(Value::Float {
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val: num,
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span: *span,
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}),
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Err(error) => Err(error.to_string().to_lowercase()),
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_examples() {
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use crate::test_examples;
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test_examples(SubCommand {})
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}
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}
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