The player speaks indices, which is the shape a file has to be
Order lists hold one-byte sequence indices and 0x80 holds a one-byte patch index. Two tables, PatchTable and SequenceTable, are the only places an address lives. THAT IS WHAT MAKES A TUNE LOADABLE WITHOUT WALKING IT. Nothing inside a sequence or an order list is an address, so putting one in memory means adding the load address to two arrays and nothing else. The alternative is a loader that parses every sequence looking for addresses to correct, which is a loader a malformed file can walk off a cliff. Doing it now, while the tune is still assembled in, means the file form and the assembled form are the same shape - so reading a tune from a file will change no engine code at all. The whole point of the rung. The patch each voice starts on moved from four calls in a row into VoiceStart, four declared bytes, and loadStartPatches reads them. A starting instrument is state and belongs where state goes: the user's ruling is that a voice with undefined state is an error, prompted by noticing that a program run a second time starts with the memory the first run left, because loading is what initialises and running is not. Order lists also halved in size, which was not the reason but is welcome. Hand-writing the two tables is exactly the tedium the compiler exists to remove - every sequence counted into its place, and moving one means renumbering. Better to feel that here than after a tool has baked the shape in. Verified by rendering: bar for bar the same piece. break.sh confirms the scaling, since an index is doubled to reach a two-byte entry and halving that step lands on the wrong sequence and fails four checks. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
This commit is contained in:
Anachronaut
co-authored by
Claude Opus 5
Claude Opus 5
parent
8029063bdc
commit
5d9b39514b
@@ -90,8 +90,13 @@ start:
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; ---- An instrument for each voice ----
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;
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; Four patches, designed in soundThing and converted by SoundPatch, which is the only thing
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; here that understands what a patch means. This reads a count and that many parameter and
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; value pairs and knows nothing else about them.
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; here that understands what a patch means. The player reads a count and that many parameter
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; and value pairs and knows nothing else about them.
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;
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; WHICH PATCH EACH VOICE STARTS ON IS DECLARED, in VoiceStart below, rather than being four
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; calls in a row here. That is the shape a tune read from a file will have - a starting
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; instrument is state and belongs in a header - and saying it once means the two forms do
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; not drift.
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;
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; A PATCH BELONGS TO ITS CHANNEL, which is why four of them can be up at once. It did not
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; used to: the LFOs belonged to the whole device, so whichever patch was loaded last owned
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@@ -99,18 +104,7 @@ start:
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; under the old device this piece would have played with the arpeggio's setting on all four
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; parts - which is exactly the fault that made Lunar Porter's low fuel warning stop
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; trilling after the first landing of a run.
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SETD.0 OboePatch
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RSTA
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CALL loadPatch ; The melody sings, so it is the one with a voice.
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SETD.0 StringsPatch
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INIA 0d1
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CALL loadPatch ; A pad underneath it.
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SETD.0 SquarePatch
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INIA 0d2
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CALL loadPatch ; And a square wave for the bass, which is where one belongs.
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SETD.0 KalimbaPatch
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INIA 0d3
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CALL loadPatch ; Plucked, for the arpeggio.
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CALL loadStartPatches
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INIA 0x60 ; Room over the top for four voices at once.
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OUTA 0x46
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@@ -208,13 +202,32 @@ tick:
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; order list, and it is worth noticing how little it cost: a table of labels the assembler
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; fills in, and ten instructions in stepVoice.
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Order0:
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Mel1 Mel2 Mel3 Mel4 0xFF 0xFF
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0d0 0d1 0d2 0d3 0xFF
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Order1:
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Har1 Har2 Har3 Har4 0xFF 0xFF
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0d4 0d5 0d6 0d7 0xFF
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Order2:
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BassC BassF BassG BassC 0xFF 0xFF
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0d8 0d9 0d10 0d8 0xFF ; BassC twice, written once.
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Order3:
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ArpC ArpF ArpG Silent 0xFF 0xFF
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0d11 0d12 0d13 0d14 0xFF
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; ---- The tables, which are the only places an address lives ----
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;
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; Writing these out by hand is exactly the tedium a compiler exists to remove: every sequence
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; has to be counted into its place above, and moving one means renumbering. That it is
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; unpleasant is the point of noticing it here rather than after a tool has baked the shape in.
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PatchTable:
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OboePatch StringsPatch SquarePatch KalimbaPatch
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SequenceTable:
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Mel1 Mel2 Mel3 Mel4 ; 0 to 3
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Har1 Har2 Har3 Har4 ; 4 to 7
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BassC BassF BassG ; 8 to 10
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ArpC ArpF ArpG Silent ; 11 to 14
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; The patch each voice starts on. Not assumed, and not four calls in a row: a starting
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; instrument is state, and state belongs somewhere it can be read.
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VoiceStart:
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0d0 0d1 0d2 0d3
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; ---- Four bars of C, F, G, C ----
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;
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@@ -239,7 +252,7 @@ Mel3:
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0d71 0d8 ; B
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0xFF
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Mel4:
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0x80 StringsPatch ; The last bar is a swell rather than a reed.
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0x80 0d1 ; Patch one is Strings: the last bar is a swell, not a reed.
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0d72 0d16 ; and home
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0xFF
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@@ -720,7 +720,7 @@ from every assembly file in it. Several are old programs written for the bare ma
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| Life | Conway's Game of Life, which had to be taught to stop, since a program that never ends takes the shell with it. Polls the console between generations. |
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| Snake | A game. Draws a whole screen with cursor addressing and steers with single keys, asking the console once a frame and never waiting. |
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| Keys | The console interrupting rather than being asked. The only one that brings a vector of its own, which is what the version two format exists for. |
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| Play | Four voices on one clock, which is what music is and one channel cannot be. The timer keeps a tick and every voice keeps its own place in its own track and its own count of how much longer the note it is holding lasts, so the parts move at four different rates and share nothing but the beat. A track is pairs of bytes, what to play and how many ticks it lasts: 1 to 127 is a MIDI note, zero is a rest, and 255 ends it - MIDI stops at 127, so neither of those had to be invented. A note's duration is its whole life and the gate goes down when the count runs out, which means a gap between two notes is written as a rest rather than invented by the player out of some fraction it decided on. Each voice loads an instrument of its own before a note is played - an oboe for the melody, strings under it, a square wave for the bass and a kalimba for the arpeggio - out of the format SoundPatch writes, which the player reads as a count and that many parameter and value pairs and understands nothing else about. Four patches can be up at once because a patch belongs to its channel; Kalimba has an LFO switched off and the other three have one on, and under a device where the LFOs belonged to the whole machine the last patch loaded would have imposed its setting on every part. A voice does not play one long track: it walks an ORDER LIST of its own, a table of sequence addresses, and takes the next one when a sequence runs out. That is where repetition comes from and it costs no notation - the bass plays the same sequence in the first bar and the last, written once. The four columns are how it reads and how a tracker would show it; per voice is how it is stored, because a voice's order cursor is then a pointer it advances by itself. A sequence can also carry commands, which take no time at all: 0x80 plays the rest of that voice on a different patch, which is how the melody's last bar becomes a swell rather than a reed. Nothing keeps the voices together except that their sequences add up to the same length, which is the first thing a compiler should check. The tune is assembled in for now; reading one from a file is what makes it a player rather than a program with one song in it, and the engine that plays it is Libraries/player.asm rather than this program. It spends over ninety nine per cent of its time asleep, because a beat is something to be woken by rather than counted up to. |
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| Play | Four voices on one clock, which is what music is and one channel cannot be. The timer keeps a tick and every voice keeps its own place in its own track and its own count of how much longer the note it is holding lasts, so the parts move at four different rates and share nothing but the beat. A track is pairs of bytes, what to play and how many ticks it lasts: 1 to 127 is a MIDI note, zero is a rest, and 255 ends it - MIDI stops at 127, so neither of those had to be invented. A note's duration is its whole life and the gate goes down when the count runs out, which means a gap between two notes is written as a rest rather than invented by the player out of some fraction it decided on. Each voice loads an instrument of its own before a note is played - an oboe for the melody, strings under it, a square wave for the bass and a kalimba for the arpeggio - out of the format SoundPatch writes, which the player reads as a count and that many parameter and value pairs and understands nothing else about. Four patches can be up at once because a patch belongs to its channel; Kalimba has an LFO switched off and the other three have one on, and under a device where the LFOs belonged to the whole machine the last patch loaded would have imposed its setting on every part. A voice does not play one long track: it walks an ORDER LIST of its own, a table of sequence addresses, and takes the next one when a sequence runs out. That is where repetition comes from and it costs no notation - the bass plays the same sequence in the first bar and the last, written once. The four columns are how it reads and how a tracker would show it; per voice is how it is stored, because a voice's order cursor is then a pointer it advances by itself. Sequence and patch names are INDICES through two tables, which are the only places an address lives - so a tune read from a file will need its base added to two arrays and nothing else, rather than a loader that walks every sequence looking for addresses to correct. A sequence can also carry commands, which take no time at all: 0x80 plays the rest of that voice on a different patch, which is how the melody's last bar becomes a swell rather than a reed. Nothing keeps the voices together except that their sequences add up to the same length, which is the first thing a compiler should check. The patch each voice starts on is declared rather than assumed, because a voice given no instrument would play on whatever the device woke up with. The tune is assembled in for now; reading one from a file is what makes it a player rather than a program with one song in it, and the engine that plays it is Libraries/player.asm rather than this program. It spends over ninety nine per cent of its time asleep, because a beat is something to be woken by rather than counted up to. |
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| Say | Prints whatever it was told, which is the shortest thing that shows osArgument working. |
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| Reboot | Starts the machine again, in 45 bytes. Writes a port rather than asking the system, because a reset has to work when the system does not. |
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| Once | Asks the loader to start something else on the next start, and only that one, in 569 bytes. |
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