vrl 0.32.0

Vector Remap Language
Documentation 
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use crate::compiler::prelude::*;
use crate::stdlib::to_float::bytes_to_float;

fn parse_float(value: Value) -> Resolved {
    bytes_to_float(value.try_bytes()?)
}

#[derive(Clone, Copy, Debug)]
pub struct ParseFloat;

impl Function for ParseFloat {
    fn identifier(&self) -> &'static str {
        "parse_float"
    }

    fn usage(&self) -> &'static str {
        "Parses the string `value` representing a floating point number in base 10 to a float."
    }

    fn category(&self) -> &'static str {
        Category::String.as_ref()
    }

    fn internal_failure_reasons(&self) -> &'static [&'static str] {
        &["`value` is not a string."]
    }

    fn return_kind(&self) -> u16 {
        kind::FLOAT
    }

    fn parameters(&self) -> &'static [Parameter] {
        const PARAMETERS: &[Parameter] = &[Parameter::required(
            "value",
            kind::BYTES,
            "The string to parse.",
        )];
        PARAMETERS
    }

    fn examples(&self) -> &'static [Example] {
        &[
            example! {
                title: "Parse negative integer",
                source: r#"parse_float!("-42")"#,
                result: Ok("-42.0"),
            },
            example! {
                title: "Parse float",
                source: r#"parse_float!("42.38")"#,
                result: Ok("42.38"),
            },
            example! {
                title: "Scientific notation",
                source: r#"parse_float!("2.5e3")"#,
                result: Ok("2500.0"),
            },
        ]
    }

    fn compile(
        &self,
        _state: &state::TypeState,
        _ctx: &mut FunctionCompileContext,
        arguments: ArgumentList,
    ) -> Compiled {
        let value = arguments.required("value");

        Ok(ParseFloatFn { value }.as_expr())
    }
}

#[derive(Debug, Clone)]
struct ParseFloatFn {
    value: Box<dyn Expression>,
}

impl FunctionExpression for ParseFloatFn {
    fn resolve(&self, ctx: &mut Context) -> Resolved {
        let value = self.value.resolve(ctx)?;

        parse_float(value)
    }

    fn type_def(&self, _: &state::TypeState) -> TypeDef {
        TypeDef::float().fallible()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    test_function![
        parse_float => ParseFloat;

        integer {
            args: func_args![value: "-42"],
            want: Ok(-42.0),
            tdef: TypeDef::float().fallible(),
        }

        float {
            args: func_args![value: "42.38"],
            want: Ok(42.38),
            tdef: TypeDef::float().fallible(),
        }

        scientific_1 {
            args: func_args![value: "2.5e3"],
            want: Ok(2500.0),
            tdef: TypeDef::float().fallible(),
        }

        scientific_2 {
            args: func_args![value: "8.543e-2"],
            want: Ok(0.08543),
            tdef: TypeDef::float().fallible(),
        }

        positive_zero {
            args: func_args![value: "+0"],
            want: Ok(0.0),
            tdef: TypeDef::float().fallible(),
        }

        negative_zero {
            args: func_args![value: "-0"],
            want: Ok(-0.0),
            tdef: TypeDef::float().fallible(),
        }

        positive_infinity {
            args: func_args![value: "inf"],
            want: Ok(f64::INFINITY),
            tdef: TypeDef::float().fallible(),
        }

        negative_infinity {
            args: func_args![value: "-inf"],
            want: Ok(f64::NEG_INFINITY),
            tdef: TypeDef::float().fallible(),
        }

        nan {
            args: func_args![value: "Nan"],
            want: Err("NaN number not supported \"Nan\"".to_string()),
            tdef: TypeDef::float().fallible(),
        }

        min {
            args: func_args![value: "-1.7976931348623157e+308"],
            want: Ok(f64::MIN),
            tdef: TypeDef::float().fallible(),
        }

        max {
            args: func_args![value: "1.7976931348623157e+308"],
            want: Ok(f64::MAX),
            tdef: TypeDef::float().fallible(),
        }

        large_string {
            args: func_args![value: "9".repeat(9999)],
            want: Ok(f64::INFINITY),
            tdef: TypeDef::float().fallible(),
        }
    ];
}