diff options
Diffstat (limited to '2d/signals.scm')
| -rw-r--r-- | 2d/signals.scm | 327 |
1 files changed, 134 insertions, 193 deletions
diff --git a/2d/signals.scm b/2d/signals.scm index 9a0c3c5..eb9f51a 100644 --- a/2d/signals.scm +++ b/2d/signals.scm @@ -25,33 +25,29 @@ #:use-module (srfi srfi-1) #:use-module (srfi srfi-9) #:use-module (srfi srfi-26) - #:use-module (2d coroutine) #:export (<signal> signal? + root-signal? make-signal + make-root-signal signal-ref signal-ref-maybe - signal-transformer - signal-filter - signal-connectors + signal-receiver + signal-connections signal-connect! signal-disconnect! signal-clear! signal-set! - signal-constant - signal-lift - signal-lift2 - signal-lift3 - signal-lift4 - signal-liftn signal-merge signal-combine + signal-do + signal-map + signal-fold + signal-filter + signal-reject signal-fold - signal-count - signal-if - signal-when - signal-unless - signal-do)) + signal-constant + signal-count)) ;;; ;;; Signals @@ -63,210 +59,155 @@ ;; programming. State mutation is hidden away and a functional, ;; declarative interface is exposed. (define-record-type <signal> - (%make-signal value transformer filter connectors) + (%make-signal value receiver connections) signal? (value signal-ref %signal-set!) - (transformer signal-transformer) - (filter signal-filter) - (connectors signal-connectors %set-signal-connectors!)) - -(define (identity-transform value old from) - "Return VALUE unchanged." - value) + (receiver signal-receiver) + (connections signal-connections %set-signal-connections!)) + +(define (make-signal init receiver . connections) + "Create a new signal with initial value INIT, a procedure RECEIVER +to transform incoming signal values and zero or more signals to +connect to." + (let ((signal (%make-signal init receiver '()))) + (for-each (cut signal-connect! <> signal) connections) + signal)) -(define (keep-all value old from) - "Keep all values." - #t) +(define (make-root-signal init) + "Create a new root level signal with initial value INIT." + (%make-signal init #f '())) -(define* (make-signal #:optional init #:key - (transformer identity-transform) - (filter keep-all) - (connectors '())) - "Create a new signal with initial value INIT that uses the given -TRANSFORMER procedure to process incoming values from another -signal. Additionally, the signal will be connected to all of the -signals in the list CONNECTORS." - (let ((signal (%make-signal init transformer filter '()))) - (for-each (cut signal-connect! <> signal) connectors) - signal)) +(define (root-signal? signal) + "Returns true if a signal has no receiver procedure or false +otherwise." + (not (signal-receiver signal))) (define (signal-ref-maybe object) - "Dereferences OBJECT if it is a signal and returns OBJECT -otherwise." + "Retrieves the signal value from OBJECT if it is a signal and or +simply returns OBJECT otherwise." (if (signal? object) (signal-ref object) object)) -(define (%signal-transform signal value from) - "Call the transform procedure for SIGNAL with VALUE." - ((signal-transformer signal) value (signal-ref signal) from)) - -(define (signal-connect! signal listener) - "Attach LISTENER to SIGNAL. When the value of SIGNAL changes, the -value will be propagated to LISTENER." - (%set-signal-connectors! - signal - (cons listener (signal-connectors signal))) - (signal-receive! listener (signal-ref signal) signal)) - -(define (signal-disconnect! signal listener) - "Detach LISTENER from SIGNAL." - (%set-signal-connectors! - signal - (delete listener (signal-connectors signal) eq?))) +(define (signal-connect! signal-in signal-out) + "Attach SIGNAL-OUT to SIGNAL-IN. When the value of SIGNAL-IN changes, the +value will be propagated to SIGNAL-OUT." + (if (root-signal? signal-out) + (error 'root-signal-error + "Cannot connect to a root signal" + signal-out) + (%set-signal-connections! + signal-in + (cons signal-out (signal-connections signal-in))))) + +(define (signal-disconnect! signal-in signal-out) + "Detach SIGNAL-OUT from SIGNAL-IN." + (%set-signal-connections! + signal-in + (delete signal-out (signal-connections signal-in) eq?))) (define (signal-clear! signal) - "Detach all connectors from SIGNAL." - (%set-signal-connectors! signal '())) + "Disconnect all connections from SIGNAL." + (%set-signal-connections! signal '())) -(define* (signal-set! signal value #:optional (from #f)) - "Set VALUE for SIGNAL from the connected signal FROM and -propagate VALUE to all connected signals. " - (let ((value (%signal-transform signal value from))) - (%signal-set! signal value) - (for-each (cut signal-receive! <> value signal) - (signal-connectors signal)))) +(define (signal-receive to from) + "Evaluate the receiver procedure for the signal TO with the signal +FROM." + ((signal-receiver to) to from)) -(define (signal-keep? signal value from) - "Call the filter procedure for SIGNAL with VALUE." - ((signal-filter signal) value (signal-ref signal) from)) +(define (signal-propagate signal) + "Notify all connected signals about the current value of SIGNAL." + (for-each (cut signal-receive <> signal) + (signal-connections signal))) -(codefine (signal-receive! signal value from) - "Receive VALUE for SIGNAL from the connected signal FROM. VALUE -will be set if it passes through the filter." - (when (signal-keep? signal value from) - (signal-set! signal value from))) +(define (signal-set! signal value) + "Change the current value of SIGNAL to VALUE and propagate SIGNAL to +all connected signals." + (%signal-set! signal value) + (signal-propagate signal)) ;;; -;;; Primitive signals +;;; Higher Order Signals ;;; -;; TODO: Write a macro for generating lifts -(define (signal-lift transformer signal) - "Create a new signal that lifts the procedure TRANSFORMER of arity 1 -onto SIGNAL." - (make-signal - #:transformer (lambda (value prev from) - (transformer value)) - #:connectors (list signal))) - -(define (signal-lift2 transformer signal1 signal2) - "Create a new signal that lifts the procedure TRANSFORMER of arity 2 -onto SIGNAL1 and SIGNAL2." - (make-signal - #:transformer (lambda (value prev from) - (transformer (signal-ref signal1) - (signal-ref signal2))) - #:connectors (list signal1 signal2))) - -(define (signal-lift3 transformer signal1 signal2 signal3) - "Create a new signal that lifts the procedure TRANSFORMER of arity 3 -onto SIGNAL1, SIGNAL2, and SIGNAL3." - (make-signal - #:transformer (lambda (value prev from) - (transformer (signal-ref signal1) - (signal-ref signal2) - (signal-ref signal3))) - #:connectors (list signal1 signal2 signal3))) - -(define (signal-lift4 transformer signal1 signal2 signal3 signal4) - "Create a new signal that lifts the procedure TRANSFORMER of arity 4 -onto SIGNAL1, SIGNAL2, SIGNAL3, and SIGNAL4." - (make-signal - #:transformer (lambda (value prev from) - (transformer (signal-ref signal1) - (signal-ref signal2) - (signal-ref signal3) - (signal-ref signal4))) - #:connectors (list signal1 signal2 signal3 signal4))) - -(define (signal-liftn transformer . signals) - "Create a new signal that lifts the procedure TRANSFORMER of arity n -onto SIGNALS where n is the size of SIGNALS." - (make-signal - #:transformer (lambda (value prev from) - (apply transformer (map signal-ref signals))) - #:connectors signals)) - (define (signal-merge . signals) - "Create a new signal that merges every signal in the list SIGNALS -into one. The value of the new signal is the value of the most -recently changed signal in the list." - (make-signal #:connectors signals)) + "Create a new signal whose value is the that of the most recently +changed signal in SIGNALs. The initial value is that of the first +signal in SIGNALS." + (apply make-signal + (signal-ref (car signals)) + (lambda (merger from) + (signal-set! merger (signal-ref from))) + signals)) (define (signal-combine . signals) - "Create a new signal that combines the values of SIGNALS into a -list." - (make-signal - #:transformer (lambda (value prev from) - (map signal-ref signals)) - #:connectors signals)) + "Create a new signal whose value is a list of the values stored in +the list SIGNALS." + (define (update) + (map signal-ref signals)) -(define (signal-fold proc init signal) - "Create a new signal that accumulates the current and previous -values of SIGNAL using PROC." - (make-signal - init - #:transformer (lambda (value prev from) - (proc value prev)) - #:connectors (list signal))) + (make-signal (update) + (lambda (combiner from) + (signal-set! combiner (update))))) -(define (signal-count signal) - "Create a new signal that increments a counter every time the value -of SIGNAL changes." - ;; Initial value is -1 to compensate for the inital signal update - ;; when connecting. - (signal-fold (lambda (new old) (1+ old)) -1 signal)) +(define (signal-do proc signal) + "Create a new signal that applies PROC when a new values is received +from SIGNAL. The value of the new signal will always be the value of +SIGNAL. This signal is a convenient way to sneak a procedure that has +a side-effect into a signal chain." + (make-signal (signal-ref signal) + (lambda (do-signal from) + (let ((value (signal-ref signal))) + (proc value) + value)))) -(define (signal-constant constant signal) - "Create a new signal that emits the value CONSTANT whenever a new -value is received from SIGNAL." - (signal-lift (lambda (value) constant) signal)) +(define (signal-map proc signal . signals) + "Create a new signal that applies PROC to the values stored in one +or more SIGNALS." + (define (update) + (apply proc (map signal-ref (cons signal signals)))) -(define (signal-if predicate consequent alternate) - "Create a new signal that emits the value of the signal CONSEQUENT -when the value of the signal PREDICATE is true and the value of the -signal ALTERNATE otherwise." - (make-signal - #:transformer (lambda (value prev from) - (if (signal-ref predicate) - (signal-ref consequent) - (signal-ref alternate))) - #:connectors (list predicate - consequent - alternate))) + (make-signal (update) + (lambda (map-signal from) + (signal-set! map-signal (update))) + signal)) -(define (signal-when predicate init consequent) - "Create a new signal that keeps the value from CONSEQUENT only when -PREDICATE is true. INIT specifies the value that is set if PREDICATE -is never true." - (make-signal - init - #:filter (lambda (value prev from) - (signal-ref predicate)) - #:transformer (lambda (value prev from) - (signal-ref consequent)) - #:connectors (list predicate consequent))) +(define (signal-fold proc init signal) + "Create a new signal that applies PROC to the values stored in +SIGNAL. PROC is applied with the current value of SIGNAL and the +previously computed value, or INIT for the first call." + (make-signal init + (let ((previous init)) + (lambda (fold-signal from) + (let ((value (proc previous (signal-ref from)))) + (set! previous value) + (signal-set! fold-signal value)))) + signal)) + +(define (signal-filter predicate default signal) + "Create a new signal that keeps an incoming value from SIGNAL when +it satifies the procedure PREDICATE. The value of the signal is +DEFAULT when the predicate is never satisfied." + (make-signal (if (predicate (signal-ref signal)) + (signal-ref signal) + default) + (lambda (filter from) + (when (predicate (signal-ref from)) + (signal-set! filter (signal-ref from)))) + signal)) + +(define (signal-reject predicate default signal) + "Create a new signal that does not keep an incoming value from +SIGNAL when it satisfies the procedure PREDICATE. The value of the +signal is DEFAULT when the predicate is never satisfied." + (signal-filter (lambda (x) (not (predicate x))) default signal)) -(define (signal-unless predicate init consequent) - "Create a new signal that drops the value from CONSEQUENT only when -PREDICATE is true. INIT specifies the value that is set if PREDICATE -is never true." - (make-signal - init - #:filter (lambda (value prev from) - (not (signal-ref predicate))) - #:transformer (lambda (value prev from) - (signal-ref consequent)) - #:connectors (list predicate consequent))) +(define (signal-constant constant signal) + "Create a new signal whose value is always CONSTANT regardless of +what the value received from SIGNAL." + (signal-map (lambda (value) constant) signal)) -(define (signal-do proc signal) - "Create a new signal that applies PROC with incoming values from -SIGNAL. The value of the new signal will always be the value of -SIGNAL. This signal is a convenient way to apply a side-effect to a -signal value." - (make-signal - #:transformer (lambda (value prev from) - (proc value) - value) - #:connectors (list signal))) +(define (signal-count signal) + "Create a new signal that increments a counter every time a new +value from SIGNAL is received." + (signal-fold + 0 (signal-constant 1 signal))) |