:sig
f64 DValue::to_f64(f64 default_value = 0) const

:params
default_value : returned when the value is missing or cannot be parsed as a number
return value : the value as a floating-point number, or `default_value`

:see
>types
0_DValue
json_decode
float_val
to_bool
to_s64
to_u64

:content
Reads a `DValue` value as a floating-point number. This is a read accessor: it is `const`, never creates or modifies nodes, and dereferences internal references automatically.

String values are trimmed and parsed permissively: numeric forms and the boolean words understood by `to_bool()` both convert. Boolean values become `1.0` or `0.0`.

`default_value` is returned when:

- the node is unset or holds an empty string
- the string does not parse as a finite number
- the node is map-shaped with more than one entry, or an unresolvable reference

A map-shaped node with exactly one entry unwraps to that entry's value before converting.

## Example

```cpp
f64 ratio = context.props["ratio"].to_f64(1.0);
f64 threshold = context.cfg.get_by_path("alerts/threshold").to_f64(0.75);
```

Use this for numeric config values, JSON-decoded fields, component props, and request data that should be treated as a number.

## Related Concepts

- PHP: `floatval()` with a fallback
- JavaScript: `parseFloat(x) || fallback`