Ouroboros is an esolang I designed this week. Time to take it for a spin!
i.1+!57*(\m1(M\1).96>.@32*-.80=\.78=3*\.66=3*\.82=5*\81=9*++++\2*1\-*+
)L!4*(4Sn1(
Each line of single-char commands1 represents an ouroboros snake, wherein execution proceeds from head (start) to tail (end) and loops back to the head. The ( and ) commands let you eat part of the tail or regurgitate it, thus changing what commands get executed. If the instruction pointer is ever swallowed, the snake dies (stops executing). An Ouroboros program consists of one or more snakes executing in parallel. Each snake has a stack of its own, and there is also a shared stack.
1One exception, which distinguishes Ouroboros from many 2D languages: multi-digit numbers can be written straightforwardly, without having to do math or push a 0 first.
Snake 1
The first snake reads a character (i) and checks whether it's -1 / EOF (.1+!). If so, it eats most of its tail, up to and including the M (57*().
The snake then swaps the character code with the tally that is above it on the stack (\), moves the tally to the shared stack (m), and swallows another character (1(). If it had already swallowed a bunch, this means it swallows the ( that the IP is currently on and dies. Otherwise, execution proceeds by moving the tally back to snake 1's stack, swapping it with the char code, and regurgitating the character that was previously swallowed (M\1)).
We then use math and stack operations to generate the appropriate score for the character. .96> tests whether it's lowercase or not; the subsequent 32*- converts to uppercase. Then the long stretch from .80= to 81=9*++++ maps P -> 1, N -> 3, etc. Finally, \2*1\-* negates the score if the letter was lowercase, and + adds it to the running tally. The snake then loops and reads another character.
Snake 2
The second snake starts with a regurgitate operation ()), which does nothing the first time through (since nothing's been swallowed yet, and also since popping an empty stack gives 0). Next, it pushes the length of the shared stack to its own stack and logically negates (L!). This gives 1 if the stack is empty, 0 otherwise. The snake multiplies by 4 and eats that many characters (4*().
If the shared stack was empty, this means the snake now ends before the S. It pushes 4 and loops back to the ), where it regurgitates the characters it just swallowed and starts over again.
If there was a value on the shared stack, however, no characters are swallowed and execution continues. The snake switches to the shared stack and outputs the number there (Sn); then it swallows its last character and dies (1().
Synchronization
The two snakes must be carefully synchronized so that there is never a value on the shared stack when snake 2 does its check, until the end of input is reached. Snake 1 puts a value on the shared stack briefly on each pass through its loop. Thus, snake 2's L command must never be executed between the m and M commands in snake 1. Fortunately, the snakes line up very well. Crucially, the length of snake 1's loop (70 instructions) is a multiple of snake 2's loop (7 instructions), so the two will never get out of sync:
i.1+!57*(\m1(M\1).96>.@32*-.80=\.78=3*\.66=3*\.82=5*\81=9*++++\2*1\-*+
)L!5*(5)L!5*(5)L!5*(5)L!5*(5)L!5*(5)L!5*(5)L!5*(5)L!5*(5)L!5*(5)L!5*(5
|__|
Danger zone
If the numbers hadn't worked out so perfectly, I would have padded one or both snakes with spaces to make them align as needed.
All of this is very well, but I want to see it in action!
Here is the above program via Stack Snippet. Even on 1000 operations per second, it takes about 10 seconds to spit out the answer for the sample input--but it does get there!
// Define Stack class
function Stack() {
this.stack = [];
this.length = 0;
}
Stack.prototype.push = function(item) {
this.stack.push(item);
this.length++;
}
Stack.prototype.pop = function() {
var result = 0;
if (this.length > 0) {
result = this.stack.pop();
this.length--;
}
return result;
}
Stack.prototype.top = function() {
var result = 0;
if (this.length > 0) {
result = this.stack[this.length - 1];
}
return result;
}
Stack.prototype.toString = function() {
return "" + this.stack;
}
// Define Snake class
function Snake(code) {
this.code = code;
this.length = this.code.length;
this.ip = 0;
this.ownStack = new Stack();
this.currStack = this.ownStack;
this.alive = true;
this.wait = 0;
this.partialString = this.partialNumber = null;
}
Snake.prototype.step = function() {
if (!this.alive) {
return null;
}
if (this.wait > 0) {
this.wait--;
return null;
}
var instruction = this.code.charAt(this.ip);
var output = null;
if (this.partialString !== null) {
// We're in the middle of a double-quoted string
if (instruction == '"') {
// Close the string and push its character codes in reverse order
for (var i = this.partialString.length - 1; i >= 0; i--) {
this.currStack.push(this.partialString.charCodeAt(i));
}
this.partialString = null;
} else {
this.partialString += instruction;
}
} else if (instruction == '"') {
this.partialString = "";
} else if ("0" <= instruction && instruction <= "9") {
if (this.partialNumber !== null) {
this.partialNumber = this.partialNumber + instruction; // NB: concatenation!
} else {
this.partialNumber = instruction;
}
next = this.code.charAt((this.ip + 1) % this.length);
if (next < "0" || "9" < next) {
// Next instruction is non-numeric, so end number and push it
this.currStack.push(+this.partialNumber);
this.partialNumber = null;
}
} else if ("a" <= instruction && instruction <= "f") {
// a-f push numbers 10 through 15
var value = instruction.charCodeAt(0) - 87;
this.currStack.push(value);
} else if (instruction == "$") {
// Toggle the current stack
if (this.currStack === this.ownStack) {
this.currStack = this.program.sharedStack;
} else {
this.currStack = this.ownStack;
}
} else if (instruction == "s") {
this.currStack = this.ownStack;
} else if (instruction == "S") {
this.currStack = this.program.sharedStack;
} else if (instruction == "l") {
this.currStack.push(this.ownStack.length);
} else if (instruction == "L") {
this.currStack.push(this.program.sharedStack.length);
} else if (instruction == ".") {
var item = this.currStack.pop();
this.currStack.push(item);
this.currStack.push(item);
} else if (instruction == "m") {
var item = this.ownStack.pop();
this.program.sharedStack.push(item);
} else if (instruction == "M") {
var item = this.program.sharedStack.pop();
this.ownStack.push(item);
} else if (instruction == "y") {
var item = this.ownStack.top();
this.program.sharedStack.push(item);
} else if (instruction == "Y") {
var item = this.program.sharedStack.top();
this.ownStack.push(item);
} else if (instruction == "\\") {
var top = this.currStack.pop();
var next = this.currStack.pop()
this.currStack.push(top);
this.currStack.push(next);
} else if (instruction == "@") {
var c = this.currStack.pop();
var b = this.currStack.pop();
var a = this.currStack.pop();
this.currStack.push(c);
this.currStack.push(a);
this.currStack.push(b);
} else if (instruction == ";") {
this.currStack.pop();
} else if (instruction == "+") {
var b = this.currStack.pop();
var a = this.currStack.pop();
this.currStack.push(a + b);
} else if (instruction == "-") {
var b = this.currStack.pop();
var a = this.currStack.pop();
this.currStack.push(a - b);
} else if (instruction == "*") {
var b = this.currStack.pop();
var a = this.currStack.pop();
this.currStack.push(a * b);
} else if (instruction == "/") {
var b = this.currStack.pop();
var a = this.currStack.pop();
this.currStack.push(a / b);
} else if (instruction == "%") {
var b = this.currStack.pop();
var a = this.currStack.pop();
this.currStack.push(a % b);
} else if (instruction == "_") {
this.currStack.push(-this.currStack.pop());
} else if (instruction == "I") {
var value = this.currStack.pop();
if (value < 0) {
this.currStack.push(Math.ceil(value));
} else {
this.currStack.push(Math.floor(value));
}
} else if (instruction == ">") {
var b = this.currStack.pop();
var a = this.currStack.pop();
this.currStack.push(+(a > b));
} else if (instruction == "<") {
var b = this.currStack.pop();
var a = this.currStack.pop();
this.currStack.push(+(a < b));
} else if (instruction == "=") {
var b = this.currStack.pop();
var a = this.currStack.pop();
this.currStack.push(+(a == b));
} else if (instruction == "!") {
this.currStack.push(+!this.currStack.pop());
} else if (instruction == "?") {
this.currStack.push(Math.random());
} else if (instruction == "n") {
output = "" + this.currStack.pop();
} else if (instruction == "o") {
output = String.fromCharCode(this.currStack.pop());
} else if (instruction == "r") {
var input = this.program.io.getNumber();
this.currStack.push(input);
} else if (instruction == "i") {
var input = this.program.io.getChar();
this.currStack.push(input);
} else if (instruction == "(") {
this.length -= Math.floor(this.currStack.pop());
this.length = Math.max(this.length, 0);
} else if (instruction == ")") {
this.length += Math.floor(this.currStack.pop());
this.length = Math.min(this.length, this.code.length);
} else if (instruction == "w") {
this.wait = this.currStack.pop();
}
// Any instruction not covered by the above cases is ignored
if (this.ip >= this.length) {
// We've swallowed the IP, so this snake dies
this.alive = false;
this.program.snakesLiving--;
} else {
// Increment IP and loop if appropriate
this.ip = (this.ip + 1) % this.length;
}
return output;
}
// Define Program class
function Program(source, speed, io) {
this.sharedStack = new Stack();
this.snakes = source.split(/\r?\n/).map(function(snakeCode) {
var snake = new Snake(snakeCode);
snake.program = this;
snake.sharedStack = this.sharedStack;
return snake;
}.bind(this));
this.snakesLiving = this.snakes.length;
this.io = io;
this.speed = speed || 10;
this.halting = false;
}
Program.prototype.run = function() {
if (this.snakesLiving) {
this.step();
this.timeout = window.setTimeout(this.run.bind(this), 1000 / this.speed);
}
}
Program.prototype.step = function() {
for (var s = 0; s < this.snakes.length; s++) {
var output = this.snakes[s].step();
if (output) {
this.io.print(output);
}
}
}
Program.prototype.halt = function() {
window.clearTimeout(this.timeout);
}
var ioFunctions = {
print: function(item) {
var stdout = document.getElementById('stdout');
stdout.value += "" + item;
},
getChar: function() {
if (inputData) {
var inputChar = inputData[0];
inputData = inputData.slice(1);
return inputChar.charCodeAt(0);
} else {
return -1;
}
},
getNumber: function() {
while (inputData && (inputData[0] < "0" || "9" < inputData[0])) {
inputData = inputData.slice(1);
}
if (inputData) {
var inputNumber = inputData.match(/\d+/)[0];
inputData = inputData.slice(inputNumber.length);
return +inputNumber;
} else {
return -1;
}
}
};
var program = null;
var inputData = null;
function resetProgram() {
var stdout = document.getElementById('stdout');
stdout.value = null;
if (program !== null) {
program.halt();
}
program = null;
inputData = null;
}
function initProgram() {
var source = document.getElementById('source'),
stepsPerSecond = document.getElementById('steps-per-second'),
stdin = document.getElementById('stdin');
program = new Program(source.value, +stepsPerSecond.innerHTML, ioFunctions);
inputData = stdin.value;
}
function runBtnClick() {
if (program === null || program.snakesLiving == 0) {
resetProgram();
initProgram();
} else {
program.halt();
var stepsPerSecond = document.getElementById('steps-per-second');
program.speed = +stepsPerSecond.innerHTML;
}
program.run();
}
function stepBtnClick() {
if (program === null) {
initProgram();
} else {
program.halt();
}
program.step();
}
.container {
width: 100%;
}
.so-box {
font-family: 'Helvetica Neue', Arial, sans-serif;
font-weight: bold;
color: #fff;
text-align: center;
padding: .3em .7em;
font-size: 1em;
line-height: 1.1;
border: 1px solid #c47b07;
-webkit-box-shadow: 0 2px 2px rgba(0, 0, 0, 0.3), 0 2px 0 rgba(255, 255, 255, 0.15) inset;
text-shadow: 0 0 2px rgba(0, 0, 0, 0.5);
background: #f88912;
box-shadow: 0 2px 2px rgba(0, 0, 0, 0.3), 0 2px 0 rgba(255, 255, 255, 0.15) inset;
}
.control {
display: inline-block;
border-radius: 6px;
float: left;
margin-right: 25px;
cursor: pointer;
}
.option {
padding: 10px 20px;
margin-right: 25px;
float: left;
}
h1 {
text-align: center;
font-family: Georgia, 'Times New Roman', serif;
}
a {
text-decoration: none;
}
input,
textarea {
box-sizing: border-box;
}
textarea {
display: block;
white-space: pre;
overflow: auto;
height: 40px;
width: 100%;
max-width: 100%;
min-height: 25px;
}
span[contenteditable] {
padding: 2px 6px;
background: #cc7801;
color: #fff;
}
#stdout-container,
#stdin-container {
height: auto;
padding: 6px 0;
}
#reset {
float: right;
}
#source-display-wrapper {
display: none;
width: 100%;
height: 100%;
overflow: auto;
border: 1px solid black;
box-sizing: border-box;
}
#source-display {
font-family: monospace;
white-space: pre;
padding: 2px;
}
.activeToken {
background: #f88912;
}
.clearfix:after {
content: ".";
display: block;
height: 0;
clear: both;
visibility: hidden;
}
.clearfix {
display: inline-block;
}
* html .clearfix {
height: 1%;
}
.clearfix {
display: block;
}
<!--
Designed and written 2015 by D. Loscutoff
Much of the HTML and CSS was taken from this Befunge interpreter by Ingo Bürk: http://codegolf.stackexchange.com/a/40331/16766
-->
<div class="container">
<textarea id="source" placeholder="Enter your program here" wrap="off">i.1+!57*(\m1(M\1).96>.@32*-.80=\.78=3*\.66=3*\.82=5*\81=9*++++\2*1\-*+
)L!4*(4Sn1(</textarea>
<div id="source-display-wrapper">
<div id="source-display"></div>
</div>
</div>
<div id="stdin-container" class="container">
<textarea id="stdin" placeholder="Input" wrap="off">5k2/ppp5/4P3/3R3p/6P1/1K2Nr2/PP3P2/8</textarea>
</div>
<div id="controls-container" class="container clearfix">
<input type="button" id="run" class="control so-box" value="Run" onclick="runBtnClick()" />
<input type="button" id="pause" class="control so-box" value="Pause" onclick="program.halt()" />
<input type="button" id="step" class="control so-box" value="Step" onclick="stepBtnClick()" />
<input type="button" id="reset" class="control so-box" value="Reset" onclick="resetProgram()" />
</div>
<div id="stdout-container" class="container">
<textarea id="stdout" placeholder="Output" wrap="off" readonly></textarea>
</div>
<div id="options-container" class="container">
<div class="option so-box">Steps per Second: <span id="steps-per-second" contenteditable>1000</span>
</div>
</div>
