6.6 KiB
Oddities
Cagire's Forth is not a classic Forth. It borrows the core ideas (stack-based evaluation, postfix notation, word definitions) but adds modern features and domain-specific extensions. If you know traditional Forth, here are the differences.
Comments
Classic Forth uses parentheses for comments:
( this is a comment )
Cagire uses double semicolons:
;; this is a comment
Everything after ;; until the end of the line is ignored.
Quotations
Classic Forth has no quotations. Code is not a value you can pass around.
Cagire has first-class quotations using curly braces:
{ dup + }
This pushes a block of code onto the stack. You can store it, pass it to other words, and execute it later. Quotations enable conditionals, probability, and cycling.
Conditionals
Classic Forth uses IF ... ELSE ... THEN:
x 0 > IF 1 ELSE -1 THEN
Cagire supports this syntax but also provides quotation-based conditionals:
{ 1 } { -1 } x 0 > ifelse
The words ? and !? execute a quotation based on a condition:
{ "kick" s . } coin ? ;; execute if coin is 1
{ "snare" s . } coin !? ;; execute if coin is 0
Strings
Classic Forth has limited string support. You print strings with .":
." Hello World"
Cagire has first-class strings:
"hello"
This pushes a string value onto the stack. Strings are used for sound names, sample names, and variable keys. You often do not need quotes at all. Any unrecognized word becomes a string automatically:
kick s . ;; "kick" is not a word, so it becomes the string "kick"
myweirdname ;; pushes "myweirdname" onto the stack
This makes scripts cleaner. You only need quotes when the string contains spaces or conflicts with a real word.
Variables
Classic Forth declares variables explicitly:
VARIABLE x
10 x !
x @
Cagire uses prefix syntax:
10 !x ;; store 10 in x
@x ;; fetch x (returns 0 if undefined)
10 ,x ;; store 10 in x, keep on stack
No declaration needed. Variables spring into existence when you store to them. ,x stores and keeps the value on the stack.
Floating Point
Classic Forth (in its original form) has no floating point. Numbers are integers. Floating point was added later as an optional extension with separate words. Cagire has native floating point:
3.14159
0.5 0.3 + ;; 0.8
Integers and floats mix freely. Division always produces a float.
Loops
Classic Forth has DO ... LOOP:
10 0 DO I . LOOP
Cagire uses a quotation-based loop with times:
4 { @i . } times ;; prints 0 1 2 3
The loop counter is stored in the variable i, accessed with @i. This fits Cagire's style where control flow uses quotations.
4 { @i 4 / at hat s . } times ;; hat at 0, 0.25, 0.5, 0.75
4 { c4 @i + note sine s . } times ;; ascending notes
For generating sequences without side effects, use .. or gen:
1 5 .. ;; pushes 1 2 3 4 5
{ dup * } 4 gen ;; pushes 0 1 4 9 (squares)
The Command Register
This is completely unique to Cagire. Traditional Forth programs print text. Cagire programs build sound commands.
The command register accumulates a sound name and parameters:
"sine" sound ;; set sound
440 freq ;; add parameter
0.5 gain ;; add parameter
. ;; emit and clear
Nothing is sent to the audio engine until you emit with .. This is unlike any classic Forth.
Context Words
Cagire provides words that read the current sequencer state:
step ;; current step index (0-127)
beat ;; current beat position
iter ;; pattern iteration count
tempo ;; current BPM
phase ;; position in bar (0-1)
These have no equivalent in classic Forth. They connect your script to the sequencer's timeline.
Probability
Classic Forth is deterministic. Cagire has built-in randomness:
{ "snare" s . } 50 prob ;; 50% chance
{ "clap" s . } 0.25 chance ;; 25% chance
{ "hat" s . } often ;; 75% chance
{ "rim" s . } sometimes ;; 50% chance
{ "tom" s . } rarely ;; 25% chance
These words take a quotation and execute it probabilistically.
Periodic Execution
Execute a quotation on specific iterations:
{ "snare" s . } 4 every ;; every 4th pattern iteration
{ "hat" s . } 3 8 bjork ;; Euclidean: 3 hits across 8 step runs
{ "hat" s . } 5 8 pbjork ;; Euclidean: 5 hits across 8 pattern iterations
every checks the pattern iteration count. On iteration 0, 4, 8, 12... the quotation runs. On all other iterations it is skipped.
bjork and pbjork use Bjorklund's algorithm to distribute k hits as evenly as possible across n positions. bjork counts by step runs, pbjork counts by pattern iterations. Classic Euclidean rhythms: tresillo (3,8), cinquillo (5,8), son clave (5,16).
Cycling
Cagire has built-in support for cycling through values. Push values onto the stack, then select one based on pattern state:
60 64 67 3 cycle note
Each time the step runs, a different note is selected. The 3 tells cycle how many values to pick from.
You can also use quotations if you need to execute code:
{ c4 note } { e4 note } { g4 note } 3 cycle
When the selected value is a quotation, it gets executed. When it is a plain value, it gets pushed onto the stack.
Two cycling words exist:
cycle- selects based onruns(how many times this step has played)pcycle- selects based oniter(how many times the pattern has looped)
The difference between cycle and pcycle matters when patterns have different lengths. cycle counts per-step, pcycle counts per-pattern.
Polyphonic Parameters
Parameter words like note, freq, and gain consume the entire stack. If you push multiple values before a param word, you get polyphony:
60 64 67 note sine s . ;; emits 3 voices with notes 60, 64, 67
This works for any param and for the sound word itself:
440 880 freq sine tri s . ;; 2 voices: sine at 440, tri at 880
When params have different lengths, shorter lists cycle:
60 64 67 note ;; 3 notes
0.5 1.0 gain ;; 2 gains (cycles: 0.5, 1.0, 0.5)
sine s . ;; emits 3 voices
Polyphony multiplies with at deltas:
0 0.5 at ;; 2 time points
60 64 note ;; 2 notes
sine s . ;; emits 4 voices (2 notes × 2 times)
Summary
Cagire's Forth is a domain-specific language for music. It keeps Forth's elegance (stack, postfix, definitions) but adapts it for live coding.