librarydemos/rosetta/Comparison.xtl

The attract mode's pace, in seconds: how long a comparison holds still before the next (long enough to read two faces of code), and how long after an interaction the stone waits before moving on its own again (long enough to look round a comparison by hand). The traversal is the nested loop for top, for idiom, for bottom: the bottom ring steps at each dwell; when it has swept every other language the drum rolls to the next idiom in the same instant, the bottom going on round; and only when every idiom has been shown does the top ring advance to the next language. So the language compared from stays put through the whole table, and no comparison comes round again within minutes (the user, 2026-10-06; before, the top stepped after each sweep of the bottom and the drum after each sweep of the top: two minutes per idiom and the same pairs again and again).

The state for i idioms and l languages, i ᶜᵐs̲tart l: nothing turned, all playing, no pointer, the attract mode ready (idle long enough already).

      ᶜᵐ⁼u̲se< "Comparison"

      31 ᶜᵐs̲tart 7
31.0 0.0 0.0 1.0 0.0
 7.0 0.0 0.0 1.0 0.0
 7.0 0.0 0.0 1.0 0.0
 0.0 0.0 0.0 0.0 0.0
20.0 0.0 0.0 0.0 0.0

The rows and columns, by name.

The picture's middle, in its own pixels (Stone's size is 420): the top half above it, the bottom half below; and how many degrees a pixel of drag turns an axis (a quarter turn across half the picture).

A cell of the state: (row c̲at col) ᶜᵐa̲t state.

The state with one cell replaced: (row c̲at col c̲at v) ᶜᵐp̲ut state (a mask over the matrix, so no cell is ever addressed by hand).

An item of an axis of n, wrapped around: item k of n for any integer k.

The item facing on an axis: 1 + its steps, wrapped.

      ᶜᵐ⁼u̲se< "Comparison"

      ᶜᵐTOP ᶜᵐc̲urrent (ᶜᵐTOP c̲at 1.0) ᶜᵐs̲tep 31 ᶜᵐs̲tart 7
2

An axis stepped by d items (1 forward, -1 back): its steps change, its angle will follow at each tick. A ring never stops on the other ring's language (the two halves always compare two languages): it steps once more the same way. (axis c̲at d) ᶜᵐs̲tep state.

      ᶜᵐ⁼u̲se< "Comparison"

      ᶜᵐIDIOM ᶜᵐc̲urrent (ᶜᵐIDIOM c̲at -1.0) ᶜᵐs̲tep 31 ᶜᵐs̲tart 7
31

      ᶜᵐBOTTOM ᶜᵐc̲urrent (ᶜᵐBOTTOM c̲at 1.0) ᶜᵐs̲tep (ᶜᵐTOP c̲at 2.0) ᶜᵐc̲hoose 31 ᶜᵐs̲tart 7
3

An axis turned to item k the short way round, and paused: choosing is navigating, turning is exploring. A ring is not turned to the other ring's language (the choice is offered disabled); the state is unchanged. (axis c̲at k) ᶜᵐc̲hoose state.

      ᶜᵐ⁼u̲se< "Comparison"

      ᶜᵐTOP ᶜᵐc̲urrent (ᶜᵐTOP c̲at 7.0) ᶜᵐc̲hoose 31 ᶜᵐs̲tart 7
7

      (ᶜᵐTOP c̲at ᶜᵐSTEPS) ᶜᵐa̲t (ᶜᵐTOP c̲at 7.0) ᶜᵐc̲hoose 31 ᶜᵐs̲tart 7
-1.0

An axis's angle eased toward 90 times its steps over dt seconds: it covers the gap in about half a second, and lands exactly when near. (axis c̲at dt) ᶜᵐe̲ase state.

      ᶜᵐ⁼u̲se< "Comparison"

      (ᶜᵐTOP c̲at ᶜᵐANGLE) ᶜᵐa̲t (ᶜᵐTOP c̲at 0.25) ᶜᵐe̲ase (ᶜᵐTOP c̲at 1.0) ᶜᵐs̲tep 31 ᶜᵐs̲tart 7
45.0

Every axis at rest where its steps put it (angles 90 times steps), for a state built by choosing before the first tick.

      ᶜᵐ⁼u̲se< "Comparison"

      ᶜᵐs̲ettle (ᶜᵐIDIOM c̲at 3.0) ᶜᵐc̲hoose 31 ᶜᵐs̲tart 7
31.0 2.0 180.0 0.0 0.0
 7.0 0.0   0.0 1.0 0.0
 7.0 0.0   0.0 1.0 0.0
 0.0 0.0   0.0 0.0 0.0
20.0 0.0   0.0 0.0 0.0

Every axis eased over dt seconds (a tick), and the attract mode's clock advanced: when the stone has been left alone long enough and the last comparison has held still for a dwell, the attract mode steps (cm:a_ttract).

      ᶜᵐ⁼u̲se< "Comparison"

      ᶜᵐBOTTOM ᶜᵐc̲urrent ᶜᵐdwell ᶜᵐt̲ick 31 ᶜᵐs̲tart 7
2

      ᶜᵐBOTTOM ᶜᵐc̲urrent (ᶜᵐdwell − 0.1) ᶜᵐt̲ick 31 ᶜᵐs̲tart 7
1

One step of the attract mode: the bottom ring steps (if it plays); when it has swept every other language (its count reaches one less than the languages), the drum rolls to the next idiom too and the bottom's count starts over; when the drum has rolled through every idiom, the top ring steps too and the drum's count starts over. A paused axis is counted but not turned, so the sweeps keep their rhythm. With 3 idioms and 4 languages: the drum rolls at every third step, the top steps at the ninth.

      ᶜᵐ⁼u̲se< "Comparison"

      s ← 3 ᶜᵐs̲tart 4

      (ᶜᵐIDIOM ᶜᵐc̲urrent ᶜᵐa̲ttract² s) c̲at ᶜᵐIDIOM ᶜᵐc̲urrent ᶜᵐa̲ttract³ s
1 2

      (ᶜᵐTOP ᶜᵐc̲urrent ᶜᵐa̲ttract⁸ s) c̲at ᶜᵐTOP ᶜᵐc̲urrent ᶜᵐa̲ttract⁹ s
1 2

      ᶜᵐIDIOM ᶜᵐc̲urrent ᶜᵐa̲ttract⁹ s
1

An axis stepped forward if it plays, else left as it is.

The stone touched: the attract mode waits again from now.

Every axis playing again (a start chosen with cm:c_hoose is paused).

The tour paused when any axis plays, else every axis resumed (the space bar: one key stops everything, and starts it again).

      ᶜᵐ⁼u̲se< "Comparison"

      (ᶜᵐTOP c̲at ᶜᵐPLAYING) ᶜᵐa̲t ᶜᵐt̲oggleTour 31 ᶜᵐs̲tart 7
0.0

      (ᶜᵐBOTTOM c̲at ᶜᵐPLAYING) ᶜᵐa̲t ᶜᵐt̲oggleTour ᶜᵐTOP ᶜᵐt̲oggle 31 ᶜᵐs̲tart 7
0.0

      (ᶜᵐTOP c̲at ᶜᵐPLAYING) ᶜᵐa̲t ᶜᵐt̲oggleTour ᶜᵐt̲oggleTour 31 ᶜᵐs̲tart 7
1.0

The tour's mode, for the host to show: "paused" when every axis is paused, "paused: top, bottom" naming the axes paused when some are, "holding" while the stone waits after a touch, else "touring".

      ᶜᵐ⁼u̲se< "Comparison"

      ᶜᵐm̲ode 31 ᶜᵐs̲tart 7
touring

      ᶜᵐm̲ode ᶜᵐt̲ouched 31 ᶜᵐs̲tart 7
holding

      ᶜᵐm̲ode ᶜᵐTOP ᶜᵐt̲oggle 31 ᶜᵐs̲tart 7
paused: top

      ᶜᵐm̲ode ᶜᵐt̲oggleTour 31 ᶜᵐs̲tart 7
paused

An axis paused or resumed.

The state after an event: a tick eases every axis; the arrow keys step the drum (Up, Down) and the top ring (Left, Right), a and d the bottom ring, space pauses or resumes the whole tour (cm:t_oggleTour), r resumes it at once, the idle wait over (cm:r_esume; the host sends it after its opening choices, since a choice pauses its axis), s the bottom ring and w the drum on their own; the pointer drags and clicks (cm:d_own, cm:m_ove, cm:u_p, cm:c_lick); a choice from the host's controls, choose AXIS ITEM, turns that axis to the item (cm:c_hoose).

The half under a point: the top ring above the middle, the bottom ring below.

The pointer pressed at a point: remembered, nothing turned yet. xy ᶜᵐd̲own state.

      ᶜᵐ⁼u̲se< "Comparison"

      4 s̲elect 100.0 50.0 ᶜᵐd̲own 31 ᶜᵐs̲tart 7
0.5 100.0 50.0 0.0 0.0

The pointer moved to a point: nothing unless it is pressed; the first move of more than a few pixels decides which axis it drags (a sideways move the half it is over, an up or down move the drum); then each move turns that axis by its distance, a drag right or down turning toward the previous item. A drag does not pause the axis for good: the stone waits cm:idleBefore seconds after any touch before moving on its own again. xy ᶜᵐm̲ove state.

      ᶜᵐ⁼u̲se< "Comparison"

      (ᶜᵐTOP c̲at ᶜᵐANGLE) ᶜᵐa̲t 142.0 50.0 ᶜᵐm̲ove 100.0 50.0 ᶜᵐd̲own 31 ᶜᵐs̲tart 7
-18.0

      (ᶜᵐBOTTOM c̲at ᶜᵐANGLE) ᶜᵐa̲t 142.0 50.0 ᶜᵐm̲ove 100.0 50.0 ᶜᵐd̲own 31 ᶜᵐs̲tart 7
0.0

The pointer released: a drag settles on the nearest item, one further along when the last move was a flick (more than 6 degrees), its steps becoming that item so the angle eases the rest of the way; a press that never moved is a click. xy ᶜᵐu̲p state.

      ᶜᵐ⁼u̲se< "Comparison"

      (ᶜᵐTOP c̲at ᶜᵐSTEPS) ᶜᵐa̲t 142.0 50.0 ᶜᵐu̲p 142.0 50.0 ᶜᵐm̲ove 100.0 50.0 ᶜᵐd̲own 31 ᶜᵐs̲tart 7
-1.0

      (ᶜᵐTOP c̲at ᶜᵐSTEPS) ᶜᵐa̲t 125.0 50.0 ᶜᵐu̲p 125.0 50.0 ᶜᵐm̲ove 120.0 50.0 ᶜᵐm̲ove 100.0 50.0 ᶜᵐd̲own 31 ᶜᵐs̲tart 7
0.0

A click on a half pauses or resumes it. xy ᶜᵐc̲lick state.

      ᶜᵐ⁼u̲se< "Comparison"

      (ᶜᵐBOTTOM c̲at ᶜᵐPLAYING) ᶜᵐa̲t 100.0 300.0 ᶜᵐc̲lick 31 ᶜᵐs̲tart 7
0.0

A key's effect: see cm:u_pdate. Named keys compare with []K_NAMED (1 Up, 2 Down, 3 Left, 4 Right); printing keys by their character.