user variables for scripted cycles

[unlessgames]

An initial draft for the discussed vars function on the cycle object.

Works similar to :map in that you can supply either a static table or a function returning a table.

I guess we'll need a different context for vars? Since variables are only being assigned once per generate instead of for each event, the fields related to single steps are meaningless.

Here, the table variant inserts the variables to the cycle directly instead of passing around the table (contrary to the case with map) whereas the callback variant follows a similar pattern to the mapping_function.

Not sure what else should happen with the callback and its errors, but it seems to work fine so far.

[github-actions]

Benchmark for f153fdf

Click to view benchmark

Test	Base	PR	%
Cycle/Generate	52.6±0.71µs	52.4±0.65µs	-0.38%
Cycle/Parse	308.2±6.75µs	318.7±5.74µs	+3.41%
Rust Phrase/Clone	434.8±5.84ns	420.0±6.61ns	-3.40%
Rust Phrase/Create	65.0±1.03µs	67.0±1.62µs	+3.08%
Rust Phrase/Run	619.6±5.92µs	626.4±8.75µs	+1.10%
Rust Phrase/Seek	127.3±231.54µs	139.1±255.27µs	+9.27%
Scripted Phrase/Clone	631.3±10.45ns	623.7±7.86ns	-1.20%
Scripted Phrase/Create	1025.9±38.01µs	995.3±18.79µs	-2.98%
Scripted Phrase/Run	1657.7±11.40µs	1641.7±16.49µs	-0.97%
Scripted Phrase/Seek	214.9±435.32µs	205.1±408.79µs	-4.56%

[github-actions]

Benchmark for c8242c9

Click to view benchmark

Test	Base	PR	%
Cycle/Generate	52.9±0.53µs	52.3±0.34µs	-1.13%
Cycle/Parse	316.3±4.35µs	311.9±4.88µs	-1.39%
Rust Phrase/Clone	429.8±8.69ns	425.6±12.07ns	-0.98%
Rust Phrase/Create	67.0±1.30µs	65.4±1.19µs	-2.39%
Rust Phrase/Run	627.1±6.42µs	645.6±4.86µs	+2.95%
Rust Phrase/Seek	132.5±242.42µs	135.7±249.90µs	+2.42%
Scripted Phrase/Clone	635.6±11.68ns	631.6±5.54ns	-0.63%
Scripted Phrase/Create	1017.4±33.02µs	1003.0±34.54µs	-1.42%
Scripted Phrase/Run	1657.1±18.77µs	1616.5±20.19µs	-2.45%
Scripted Phrase/Seek	215.0±434.49µs	203.8±407.01µs	-5.21%

[github-actions]

Benchmark for 77adad2

Click to view benchmark

Test	Base	PR	%
Cycle/Generate	52.0±0.34µs	52.5±1.54µs	+0.96%
Cycle/Parse	315.8±6.34µs	309.2±4.24µs	-2.09%
Rust Phrase/Clone	431.8±7.61ns	426.8±6.61ns	-1.16%
Rust Phrase/Create	66.6±1.74µs	65.7±2.05µs	-1.35%
Rust Phrase/Run	639.5±14.46µs	645.6±6.08µs	+0.95%
Rust Phrase/Seek	127.7±231.26µs	136.8±253.06µs	+7.13%
Scripted Phrase/Clone	637.1±6.87ns	637.9±11.71ns	+0.13%
Scripted Phrase/Create	994.8±18.35µs	1011.6±67.51µs	+1.69%
Scripted Phrase/Run	1665.4±11.42µs	1637.2±10.42µs	-1.69%
Scripted Phrase/Seek	216.2±437.92µs	214.0±433.11µs	-1.02%

[emuell]

Looks great. I'll add a few nitpicking comments in the review and will do more testing over the weekend. Else this looks straight forward and like a really great addition!

[unlessgames]

Hey, did you mean that you wanted to add those comments to this as-is, or are you waiting for me here to make the PR more complete? I'd appreciate any nitpicks here before continuing!

[emuell]

There should be a new with_variables_callback instead of adding this into the existing off-topic with_mapping_callback. I can fix that too if you want me to.