:sig
function s64(value : as string, opt : dval = {}) s64

:params
value : scalar value or text to convert
opt : options map with `fallback` and `base`

:returns
A signed 64-bit integer, or `opt.fallback`.

:content
`s64()` converts the exact text from `value`. It uses base 10 unless `opt.base` selects another integer base. `opt.fallback` is the result for empty text or text that does not parse. It defaults to `0`.

`value` accepts scalar values through `as string`. The conversion keeps scalar text exact. Empty and missing `dval` values both convert to empty text. Use `value?` before conversion when presence matters. An empty value is present, but a missing value is not.

The options map accepts only `fallback` and `base`. An unknown key is an error.

:example capy render
print(s64("2a", base: 16, fallback: -1), "\n")

:see-group
constructors
