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//! # ksl::builtin::string_case
//!
//! Built-in function `Uppercase` and `Lowercase`.
use crate::{Environment, eval::apply::eval_apply, value::Value};
pub(crate) fn builtin(args: &[Value], is_upper: bool, env: &Environment) -> Option<(Value, Environment)> {
if let [val] = &args[..] {
match eval_apply(val, env) {
Some((Value::String(s), _)) => Some((
Value::String(if is_upper {
s.to_uppercase()
} else {
s.to_lowercase()
}),
Environment::new(),
)),
Some((e, _)) => {
eprintln!(
concat!(
"Error[ksl::builtin::string_case]: ",
"Expected a string, but got `{:?}`."
),
e
);
None
}
None => {
eprintln!(
concat!(
"Error[ksl::builtin::string_case]: ",
"Cannot evaluate expression {:?}."
),
val
);
None
}
}
} else {
eprintln!(
concat!(
"Error[ksl::builtin::string_case]: ",
"Only accepts 1 argument, but {} were passed."
),
args.len()
);
None
}
}