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javascript - Brainfuck 解释器的错误行为

转载 作者:行者123 更新时间:2023-11-29 19:02:34 26 4
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我有以下正在通过最小测试套件的 Brainfuck 解释器。除了一个相当大的问题,比如打印斐波那契数列似乎失败了(套件中的最后一个测试)。我解释执行失败的 brainfuck fibonacci 代码来自 http://esoteric.sange.fi/brainfuck/bf-source/prog/fibonacci.txt . 我的解释有什么问题?这是一个 fiddle :https://jsfiddle.net/rt017kpz/

function brainLuck(code, input) {
// "Infinite" heap of memory initialized as 0 for bf to store program values
let data = new Proxy([], {get: (arr, i) => arr[i] ? arr[i] : 0 })
let ptr = 0;
let inputPtr = 0;
let codePtr = 0;
let output = '';
let loopStack = []

const op = {
'+' : () => {
if (data[ptr] === 255) { data[ptr] = 0; }
else { data[ptr]++; }
codePtr++;
},
'-' : () => {
if (data[ptr] === 0) { data[ptr] = 255; }
else { data[ptr]--; }
codePtr++;
},
'.' : () => {
output += String.fromCharCode(data[ptr]);
codePtr++;
},
',' : () => {
data[ptr] = input.charCodeAt(inputPtr++);
codePtr++;
},
'>' : () => {
ptr++; codePtr++;
},
'<' : () => {
if (ptr > 0) { ptr--; }
codePtr++;
},
'[' : () => {
if (data[ptr] === 0) {
while(code[codePtr] !== ']') codePtr++;
} else {
loopStack.unshift(codePtr);
}
codePtr++
},
']' : () => {
if (data[ptr] === 0) { loopStack.shift(); }
else { codePtr = loopStack[0] }
codePtr++
}
}

while(codePtr < code.length) {
if(op[code[codePtr]]) op[code[codePtr]]()
else codePtr++
}
return output;
}



////////// TESTS //////////////

it('handles `+` and `.` operants', () => {
expect(
brainLuck('+++.')
).to.equal(
String.fromCharCode(3)
)
})

it('handles `-` operant and underflows from 0 to 255', () => {
expect(
brainLuck('+++----.')
).to.equal(
String.fromCharCode(255)
)
})

it('handles `,` the input operand', () => {
expect(
brainLuck(',.', 'A')
).to.equal(
'A'
)
})

it('handles input in conjuction with arithmetic', () => {
expect(
brainLuck(',+.', 'A')
).to.equal(
'B'
)
})

it('handles looping (`[`, `]`) and shift (`<`, `>`) operants', () => {
expect(
brainLuck(',>+++[<.>-]', 'A')
).to.equal(
'AAA'
)
})

it('only parses known symbols', () => {
expect(
brainLuck(',nothing>++else+[<.>matters!-]', 'A')
).to.equal(
'AAA'
)
})

it('handles nested loops', () => {
expect(
brainLuck(',>+++[->+++[<<.>>-]<]', 'A')
).to.equal(
'AAAAAAAAA'
)
})

it('can multiply two numbers', () => {
expect(
brainLuck(',>,<[>[->+>+<<]>>[-<<+>>]<<<-]>>.', String.fromCharCode(8,9))
).to.equal(
String.fromCharCode(72)
)
})

it('can print the fibonacci sequence', () => {
expect(
brainLuck('++++>+>>>>++++++++++++++++++++++++++++++++++++++++++++>++++++++++++++++++++++++++++++++<<<<<<[>[>>>>>>+>+<<<<<<<-]>>>>>>>[<<<<<<<+>>>>>>>-]<[>++++++++++[-<-[>>+>+<<<-]>>>[<<<+>>>-]+<[>[-]<[-]]>[<<[>>>+<<<-]>>[-]]<<]>>>[>>+>+<<<-]>>>[<<<+>>>-]+<[>[-]<[-]]>[<<+>>[-]]<<<<<<<]>>>>>[++++++++++++++++++++++++++++++++++++++++++++++++.[-]]++++++++++<[->-<]>++++++++++++++++++++++++++++++++++++++++++++++++.[-]<<<<<<<<<<<<[>>>+>+<<<<-]>>>>[<<<<+>>>>-]<-[>>.>.<<<[-]]<<[>>+>+<<<-]>>>[<<<+>>>-]<<[<+>-]>[<+>-]<<<-]')
).to.equal(
'1, 1, 2, 3'
)
})


mocha.run();
<html>
<head>
<meta charset="utf-8">
<title>Mocha Tests</title>
<link href="https://cdn.rawgit.com/mochajs/mocha/2.2.5/mocha.css" rel="stylesheet" />
</head>
<body>
<div id="mocha"></div>
<script src="https://cdn.rawgit.com/Automattic/expect.js/0.3.1/index.js"></script>
<script src="https://cdn.rawgit.com/mochajs/mocha/2.2.5/mocha.js"></script>
<script>mocha.setup('bdd')</script>
</body>
</html>

最佳答案

[ 的实现搜索第一个 ] 而不是匹配的 ],后者可能是第二个、第三个、第四个等等. ] 符号。您需要在扫描时对它们进行计数。以下代码段具有执行此操作的 [ 的实现,并且 fib 测试现在可以运行:

function brainLuck(code, input) {
// "Infinite" heap of memory initialized as 0 for bf to store program values
let data = new Proxy([], {get: (arr, i) => arr[i] ? arr[i] : 0 })
let ptr = 0;
let inputPtr = 0;
let codePtr = 0;
let output = '';
let loopStack = []

const op = {
'+' : () => {
if (data[ptr] === 255) { data[ptr] = 0; }
else { data[ptr]++; }
codePtr++;
},
'-' : () => {
if (data[ptr] === 0) { data[ptr] = 255; }
else { data[ptr]--; }
codePtr++;
},
'.' : () => {
output += String.fromCharCode(data[ptr]);
codePtr++;
},
',' : () => {
data[ptr] = input.charCodeAt(inputPtr++);
codePtr++;
},
'>' : () => {
ptr++; codePtr++;
},
'<' : () => {
if (ptr > 0) { ptr--; }
codePtr++;
},
'[' : () => {
if (data[ptr] === 0) {
let level = 0;
while(code[codePtr] !== ']' || level > 1) {
if (code[codePtr] === '[')
level += 1;
if (code[codePtr] === ']')
level -= 1;
codePtr++;
}
} else {
loopStack.unshift(codePtr);
}
codePtr++
},
']' : () => {
if (data[ptr] === 0) { loopStack.shift(); }
else { codePtr = loopStack[0] }
codePtr++
}
}

while(codePtr < code.length) {
if(op[code[codePtr]]) op[code[codePtr]]()
else codePtr++
}
return output;
}



////////// TESTS //////////////

it('handles `+` and `.` operants', () => {
expect(
brainLuck('+++.')
).to.equal(
String.fromCharCode(3)
)
})

it('handles `-` operant and underflows from 0 to 255', () => {
expect(
brainLuck('+++----.')
).to.equal(
String.fromCharCode(255)
)
})

it('handles `,` the input operand', () => {
expect(
brainLuck(',.', 'A')
).to.equal(
'A'
)
})

it('handles input in conjuction with arithmetic', () => {
expect(
brainLuck(',+.', 'A')
).to.equal(
'B'
)
})

it('handles looping (`[`, `]`) and shift (`<`, `>`) operants', () => {
expect(
brainLuck(',>+++[<.>-]', 'A')
).to.equal(
'AAA'
)
})

it('only parses known symbols', () => {
expect(
brainLuck(',nothing>++else+[<.>matters!-]', 'A')
).to.equal(
'AAA'
)
})

it('handles nested loops', () => {
expect(
brainLuck(',>+++[->+++[<<.>>-]<]', 'A')
).to.equal(
'AAAAAAAAA'
)
})

it('can multiply two numbers', () => {
expect(
brainLuck(',>,<[>[->+>+<<]>>[-<<+>>]<<<-]>>.', String.fromCharCode(8,9))
).to.equal(
String.fromCharCode(72)
)
})

it('can print the fibonacci sequence', () => {
expect(
brainLuck('++++>+>>>>++++++++++++++++++++++++++++++++++++++++++++>++++++++++++++++++++++++++++++++<<<<<<[>[>>>>>>+>+<<<<<<<-]>>>>>>>[<<<<<<<+>>>>>>>-]<[>++++++++++[-<-[>>+>+<<<-]>>>[<<<+>>>-]+<[>[-]<[-]]>[<<[>>>+<<<-]>>[-]]<<]>>>[>>+>+<<<-]>>>[<<<+>>>-]+<[>[-]<[-]]>[<<+>>[-]]<<<<<<<]>>>>>[++++++++++++++++++++++++++++++++++++++++++++++++.[-]]++++++++++<[->-<]>++++++++++++++++++++++++++++++++++++++++++++++++.[-]<<<<<<<<<<<<[>>>+>+<<<<-]>>>>[<<<<+>>>>-]<-[>>.>.<<<[-]]<<[>>+>+<<<-]>>>[<<<+>>>-]<<[<+>-]>[<+>-]<<<-]')
).to.equal(
'1, 1, 2, 3'
)
})


mocha.run();
<html>
<head>
<meta charset="utf-8">
<title>Mocha Tests</title>
<link href="https://cdn.rawgit.com/mochajs/mocha/2.2.5/mocha.css" rel="stylesheet" />
</head>
<body>
<div id="mocha"></div>
<script src="https://cdn.rawgit.com/Automattic/expect.js/0.3.1/index.js"></script>
<script src="https://cdn.rawgit.com/mochajs/mocha/2.2.5/mocha.js"></script>
<script>mocha.setup('bdd')</script>
</body>
</html>

关于javascript - Brainfuck 解释器的错误行为,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45774767/

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