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Support negative index counting from end.

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This commit is contained in:
Stephen Chung
2021-04-10 15:00:03 +08:00
parent 716e9cf779
commit 40fda5139d
9 changed files with 273 additions and 83 deletions
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56
src/engine.rs
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@@ -1598,15 +1598,29 @@ impl Engine {
let arr_len = arr.len();
if index >= 0 {
arr.get_mut(index as usize)
.map(Target::from)
.ok_or_else(|| {
EvalAltResult::ErrorArrayBounds(arr_len, index, idx_pos).into()
})
let arr_idx = if index < 0 {
// Count from end if negative
arr_len
- index
.checked_abs()
.ok_or_else(|| {
Box::new(EvalAltResult::ErrorArrayBounds(arr_len, index, idx_pos))
})
.and_then(|n| {
if n as usize > arr_len {
Err(EvalAltResult::ErrorArrayBounds(arr_len, index, idx_pos)
.into())
} else {
Ok(n as usize)
}
})?
} else {
EvalAltResult::ErrorArrayBounds(arr_len, index, idx_pos).into()
}
index as usize
};
arr.get_mut(arr_idx)
.map(Target::from)
.ok_or_else(|| EvalAltResult::ErrorArrayBounds(arr_len, index, idx_pos).into())
}
#[cfg(not(feature = "no_object"))]
@@ -1634,15 +1648,27 @@ impl Engine {
.as_int()
.map_err(|err| self.make_type_mismatch_err::<crate::INT>(err, idx_pos))?;
if index >= 0 {
let (ch, offset) = if index >= 0 {
let offset = index as usize;
let ch = s.chars().nth(offset).ok_or_else(|| {
EvalAltResult::ErrorStringBounds(chars_len, index, idx_pos)
})?;
Ok(Target::StringChar(target, offset, ch.into()))
(
s.chars().nth(offset).ok_or_else(|| {
EvalAltResult::ErrorStringBounds(chars_len, index, idx_pos)
})?,
offset,
)
} else if let Some(index) = index.checked_abs() {
let offset = index as usize;
(
s.chars().rev().nth(offset - 1).ok_or_else(|| {
EvalAltResult::ErrorStringBounds(chars_len, index, idx_pos)
})?,
offset,
)
} else {
EvalAltResult::ErrorStringBounds(chars_len, index, idx_pos).into()
}
return EvalAltResult::ErrorStringBounds(chars_len, index, idx_pos).into();
};
Ok(Target::StringChar(target, offset, ch.into()))
}
#[cfg(not(feature = "no_index"))]