Skip to content

perf(core): reduce redundant grapheme conversions in common_prefix/suffix #7

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
lupodevelop merged 1 commit into from
Jan 2, 2026
Merged

perf(core): reduce redundant grapheme conversions in common_prefix/suffix #7

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
32 changes: 17 additions & 15 deletions src/str/core.gleam
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -926,7 +926,8 @@ pub fn common_prefix(strings: List(String)) -> String {
[single] -> single
[first, ..rest] -> {
let first_chars = string.to_graphemes(first)
find_common_prefix(first_chars, rest, [])
let others_chars = list.map(rest, string.to_graphemes)
find_common_prefix(first_chars, others_chars, [])
|> list.reverse
|> string.concat
}
Expand All @@ -935,15 +936,15 @@ pub fn common_prefix(strings: List(String)) -> String {

fn find_common_prefix(
reference: List(String),
others: List(String),
others: List(List(String)),
acc: List(String),
) -> List(String) {
case reference {
[] -> acc
[char, ..rest_ref] -> {
let all_have_char =
list.all(others, fn(s) {
case string.to_graphemes(s) {
list.all(others, fn(graphemes) {
case graphemes {
[] -> False
[first, ..] -> first == char
}
Expand All @@ -952,9 +953,7 @@ fn find_common_prefix(
False -> acc
True -> {
let new_others =
list.map(others, fn(s) {
s |> string.to_graphemes |> list.drop(1) |> string.concat
})
list.map(others, fn(graphemes) { list.drop(graphemes, 1) })
find_common_prefix(rest_ref, new_others, [char, ..acc])
}
}
Expand All @@ -968,14 +967,17 @@ fn find_common_prefix(
/// common_suffix(["hello", "world"]) -> ""
///
pub fn common_suffix(strings: List(String)) -> String {
strings
|> list.map(fn(s) {
s |> string.to_graphemes |> list.reverse |> string.concat
})
|> common_prefix
|> string.to_graphemes
|> list.reverse
|> string.concat
case strings {
[] -> ""
[single] -> single
[first, ..rest] -> {
let first_chars = string.to_graphemes(first) |> list.reverse
let others_chars =
list.map(rest, fn(s) { string.to_graphemes(s) |> list.reverse })
find_common_prefix(first_chars, others_chars, [])
|> string.concat
}
}
}

// ============================================================================
Expand Down