Seteable Tempo

src/classes/Scheduler.js

@@ -55,6 +55,7 @@ export default class Scheduler {
 		this.currentTime = timestamp;
 
 		this.interval = setInterval(() => {
+			const rhythmMapObj = rhythmMap()
 			while (this.currentTime < context.currentTime + this.lookahead) {
 				// The tick length could be a number or a string that starts
 				// with 'r', indicating a rest.
@@ -65,7 +66,7 @@ export default class Scheduler {
 				if (typeof nextTickLength === 'string' && nextTickLength.charAt(0).toLowerCase() === 'r') {
 					rest = true;
 					// Convert it into the appropriate rhythm.
-					nextTickLength = rhythmMap[nextTickLength.substr(1)];
+					nextTickLength = rhythmMapObj[nextTickLength.substr(1)];
 				}
 				// We're only ticking on beats that aren't rests.
 				if (!rest) {

src/editor.js

@@ -59,7 +59,7 @@ const existingCode = window.localStorage.getItem('code');
 const defaultCode = `# Welcome to Slang! Here's an example to get you started.
 # Click the Run button above to start playing this code.
 
-tempo 200
+TEMPO 200
 
 # Make a sound called @synth with a triangle wave
 @synth (adsr (osc tri) 64n 8n 0.5 8n)

src/functions/transpose.js

@@ -15,6 +15,8 @@ export default class Transpose extends FunctionCall {
 		this.hasWarned = false;
 	}
 	next(passedValue) {
+		const rhythmMapObj = rhythmMap();
+		console.log(rhythmMapObj);
 		let nextValue = passedValue || this.data.next();
 
 		// Unfortunately transposing rhythms won't work
@@ -30,7 +32,7 @@ export default class Transpose extends FunctionCall {
 			typeof nextValue === 'string'
 			&& (
 				nextValue.charAt(0).toLowerCase() === 'r'
-				|| rhythmMap[nextValue]
+				|| rhythmMapObj[nextValue]
 			)
 		) {
 			if (!this.hasWarned) {

src/helpers/parseArguments.js

@@ -1,23 +1,25 @@
 import List from './List';
 import FunctionCall from '../functions';
 
-const TEMPO = 120;
-const DIVISION = (1 / 24) / (TEMPO / 60);
-
-export const rhythmMap = {
-	'64t': DIVISION,
-	'64n': DIVISION * 1.5,
-	'32t': DIVISION * 2,
-	'32n': DIVISION * 3,
-	'16t': DIVISION * 4,
-	'16n': DIVISION * 6,
-	'8t': DIVISION * 8,
-	'8n': DIVISION * 12,
-	'4t': DIVISION * 16,
-	'4n':DIVISION * 24,
-	'2t': DIVISION * 32,
-	'2n': DIVISION * 48,
-	'1n': DIVISION * 96,
+let TEMPO = 120;
+
+export function rhythmMap () {
+	const DIVISION = (1 / 24) / (TEMPO / 60);
+	return {
+		'64t': DIVISION,
+		'64n': DIVISION * 1.5,
+		'32t': DIVISION * 2,
+		'32n': DIVISION * 3,
+		'16t': DIVISION * 4,
+		'16n': DIVISION * 6,
+		'8t': DIVISION * 8,
+		'8n': DIVISION * 12,
+		'4t': DIVISION * 16,
+		'4n': DIVISION * 24,
+		'2t': DIVISION * 32,
+		'2n': DIVISION * 48,
+		'1n': DIVISION * 96,
+	};
 }
 
 /*
@@ -52,10 +54,17 @@ export function parseArgument(arg) {
 
 	return null;
 }
+export function changeTempo(tempo) {
+	let min = 30;
+	let max = 500;
+	const newTempo = Math.max(Math.min(tempo, max), min);
+	TEMPO = isNaN(newTempo) ? TEMPO : newTempo;
+}
 
 function createArgumentFromStaticValue(value) {
+	const rhythmMapObj = rhythmMap()
 	// convert rhythms into numbers if we catch one
 	return {
-		next: () => rhythmMap[value] || value,
+		next: () => rhythmMapObj[value] || value,
 	};
 }

src/runtime.js

@@ -1,5 +1,6 @@
 import Sound from './classes/Sound';
 import context from './helpers/context';
+import { changeTempo } from './helpers/parseArguments.js';
 
 const model = {
 	sounds: {},
@@ -17,6 +18,9 @@ function runScene(scene) {
 			case 'play':
 				parsePlay(operation);
 				break;
+			case 'tempo':
+				parseTempo(operation);
+				break;
 		}
 	});
 
@@ -55,6 +59,11 @@ function parsePlay(operation) {
 	model.sounds[operation.sound.name].schedule(operation.patterns);
 }
 
+function parseTempo(operation) {
+	console.log(operation);
+	changeTempo(operation.value);
+}
+
 function clearScene() {
 	Object.keys(model.sounds).forEach((id) => {
 		model.sounds[id].destroy();

src/slang.js

@@ -90,7 +90,7 @@ semantics.addOperation('toAST', {
 	Tempo(kw, value) {
 		return {
 			type: 'tempo',
-			value,
+			value: value.toAST()
 		};
 	},
 

src/slang.ohm

@@ -73,8 +73,8 @@ Sound {
     the sound beats per minute.
   */
 
-  Tempo = TempoKeyword tempoPrim
-  TempoKeyword = "tempo" | "[]"
+  Tempo = TempoKeyword int
+  TempoKeyword = "TEMPO" | "|"
 
   /*
     PLAY LINES
@@ -116,7 +116,6 @@ Sound {
     | "-"? digit+ -- int
 
   int = "-"? digit+
-  tempoPrim = digit+
 
   note = letter "#" digit+ -- sharp
     | letter "b" digit+ -- flat