Migrate to new roc by ageron · Pull Request #198 · exercism/roc

ageron · 2026-06-21T01:18:09Z

This PR migrates the Roc track to the new zig-based Roc compiler and its new syntax.

At the time of writing:

92 exercises have been migrated and all their tests pass.
4 exercises have been migrated but compilation fails: alphametics, complex-numbers, protein-translation and strain.
14 exercises are partially migrated (i.e., only the tests):
- 7 exercises shouldn't be too hard to finish migrating: forth, go-counting, grep, poker, rational-numbers, tournament, and zebra-puzzle.
- 7 exercises depend on external libraries, so they will be impossible to migrate until these libraries are migrated. This includes anagram (unicode), gigasecond (isodate), meetup (isodate), micro-blog (unicode), rest-api (json), reverse-string (unicode) and sgf-parsing (roc-parser)

… nothing

…xercises/practice

…iler

github-actions · 2026-06-21T01:18:19Z

This PR touches files which potentially affect the outcome of the tests of an exercise. This will cause all students' solutions to affected exercises to be re-tested.

If this PR does not affect the result of the test (or, for example, adds an edge case that is not worth rerunning all tests for), please add the following to the merge-commit message which will stops student's tests from re-running. Please copy-paste to avoid typos.

[no important files changed]

For more information, refer to the documentation. If you are unsure whether to add the message or not, please ping @exercism/maintainers-admin in a comment. Thank you!

Anton-4 · 2026-06-21T12:31:02Z

+app [main!] {
+    pf: platform "https://github.com/lukewilliamboswell/roc-platform-template-zig/releases/download/0.7/DuRUyJh31Gt41YArMcVcvybLa2bCWboccWQ7Zq1KZPZ6.tar.zst"


roc-platform-template-zig 0.8 is already out, it is possible that you need 0.9 (not out yet) with the latest Roc nightly due to https://roc.zulipchat.com/#narrow/channel/397893-announcements/topic/nominal.20field.20ordering.20is.20now.20preserved/near/605353849

Anton-4 · 2026-06-21T12:41:50Z

+		?? ""
+}
+
+# List.reverse should soon be available in Roc's builtins


List.rev is available now.

Anton-4 · 2026-06-21T13:44:00Z

+	result = solve("I + BB == ILL")
+	Set.from_list(result ?? []) == Set.from_list(


We typically like to steer people away from using ?? for default value fallbacks because they fail silently.
I just tried changing it to:

result = solve("I + BB == ILL")?

And that works in both cases Err or Ok.

Here the silent failure is not a problem of course but we want to make sure people don't see this as the way to handle errors in Roc.

Anton-4 · 2026-06-21T14:21:10Z

 app [main!] {
-    pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.20.0/X73hGh05nNTkDHU06FHC0YfFaQB1pimX7gncRcao5mU.tar.br",
-    unicode: "https://github.com/roc-lang/unicode/releases/download/0.3.0/9KKFsA4CdOz0JIOL7iBSI_2jGIXQ6TsFBXgd086idpY.tar.br",
+	pf: platform "https://github.com/lukewilliamboswell/roc-platform-template-zig/releases/download/0.7/DuRUyJh31Gt41YArMcVcvybLa2bCWboccWQ7Zq1KZPZ6.tar.zst",


This one should be updated to latest release as well.

Anton-4 · 2026-06-21T14:27:22Z

-    result = [1, 3, 4, 6, 8, 9, 11] |> find(6)
-    result == Ok(3)
+expect {
+	result = [1, 3, 4, 6, 8, 9, 11]->find(6)


We typically write this as result = find([1, 3, 4, 6, 8, 9, 11], 6), that looks more familiar to most people.

Anton-4 · 2026-06-21T14:32:43Z

+	rolls.fold_until(
+		Ok(new_game),
+		|state, pins| {
+			match state {
+				Ok(game) => {
+					match game.roll(pins) {
+						Ok(updated_game) => Continue(Ok(updated_game))
+						Err(err) => Break(Err(err))
+					}
+				}
+				Err(_) => {
+					crash "Impossible, we don't start or continue with an Err"
+				}
+			}
+		},
+	)


Turning this into a for loop would probably make it easier to understand.

Anton-4 · 2026-06-21T14:36:06Z

-    result == Ok([1])
+expect {
+	coins = [1, 5, 10, 25]
+	result = coins->find_fewest_coins(1)


Same as before, it should preferably be find_fewest_coins(coins, 1)

Anton-4 · 2026-06-21T14:44:11Z

+expect {
+	_result = CircularBuffer.create({ capacity: 1 })
+		.write(
+			1,
+		)?
+		.read()?
+		->expect_value(1)
+
+	Bool.True
+}


This looks unconventional, I personally would prefer more duplication that is easier to understand.

Anton-4 · 2026-06-21T15:45:18Z

 app [main!] {
-    pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.20.0/X73hGh05nNTkDHU06FHC0YfFaQB1pimX7gncRcao5mU.tar.br",
-    isodate: "https://github.com/imclerran/roc-isodate/releases/download/v0.6.2/73w_H-aSJNcWqtXvMG4JQw_HoaApMBLnE92XD4OcVGU.tar.br",
+	pf: platform "https://github.com/lukewilliamboswell/roc-platform-template-zig/releases/download/0.7/DuRUyJh31Gt41YArMcVcvybLa2bCWboccWQ7Zq1KZPZ6.tar.zst",


Another one to update to the latest version.

ageron added 30 commits June 9, 2026 16:55

Update exercise to new compiler: accumulate

d66659f

Update bin/*, config/*, and docs/* to new Roc

6223042

Replace 'roc format' with 'roc fmt' and format accumulate-test.roc

30ff50e

Format Accumulate.roc and its Example.roc

6bf2a73

Update exercise to new compiler: acronym

9438c21

Format acronym/.meta/Example.roc

28f4a81

Use default platform unless additional libraries are used

bac505e

Update exercise to new compiler: affine-cipher

d3fd9b2

Reorder future builtin functions

09a2d96

roc fmt affine-cipher .roc files

5163814

Update exercise to new compiler: all-your-base

a85d197

Update exercise to new compiler: allergies

5fe5896

Simplify match

d2afec3

Update exercise to new compiler: armstrong-numbers

0d9e336

Move main! to the end of the *-test.roc files and explain why it does…

8047962

… nothing

Update exercise to new compiler: atbash-cipher

dfd24c7

Update exercise to new compiler: binary

02aeed9

Remove unneeded parentheses

cc50a12

Always use the same 'Please implement' message

d4e75a0

Add footer at the end of each template.j2

22d5c88

Update exercise to new compiler: circular-buffer

6692385

Upgrade all .meta/template.j2 and *-test.roc files to new compiler

ac32d80

Fix to_roc_multiline_string Jinja filter, and skip non-dir files in e…

d2181f0

…xercises/practice

Update exercise to new compiler: binary-search

e493437

Change Bool.true/false to Bool.True/False

a4de383

Replace Num.log(2), Num.pi, Num.e with float values

af94237

Upgrade modules to the new type module format (first step)

0f199c3

Update exercise to new compiler: bob

8300bda

Update exercise to new compiler: bowling

6043ce5

Update exercise to new compiler: change

4e89774

ageron added 17 commits June 19, 2026 23:12

Update exercise to new compiler: rail-fence-cipher

3fb6b94

Update exercise to new compiler: flower-field

4bcb588

Update exercise to new compiler: minesweeper

03a039e

Update exercise to new compiler: yacht

b866a79

Update exercise to new compiler: rectangles

5234778

Update exercise to new compiler: palindrome-products

4f41d8d

Update exercise to new compiler: food-chain

66256e8

Update exercise to new compiler: error-handling

b84f37d

Update exercise to new compiler: custom-set

6ca60fc

Update exercise to new compiler: list-ops

d7074ff

Remove Temp.roc

f713c3b

Upgrade to latest roc version and fix a few minor issues

c48ca5e

Update exercise to new compiler: say

61c2095

Update exercise to new compiler: word-search

b2c8284

Update exercise to new compiler: ocr-numbers

d173ab5

Merge remote-tracking branch 'upstream/main' into migrate-to-zig-comp…

ace6f65

…iler

Update exercise to new compiler: two-bucket

1daeb1a

ageron added 2 commits June 22, 2026 00:22

Update exercise to new compiler: simple-linked-list

a40b753

Update the exercise stub for simple-linked-list

bde2f9c

Anton-4 reviewed Jun 21, 2026

View reviewed changes

Remove old test file for simple-linked-list

0e7604f

Anton-4 reviewed Jun 21, 2026

View reviewed changes

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Migrate to new roc#198

Migrate to new roc#198
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		app [main!] {
		pf: platform "https://github.com/lukewilliamboswell/roc-platform-template-zig/releases/download/0.7/DuRUyJh31Gt41YArMcVcvybLa2bCWboccWQ7Zq1KZPZ6.tar.zst"

		result = solve("I + BB == ILL")
		Set.from_list(result ?? []) == Set.from_list(

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ageron commented Jun 21, 2026 •

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