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Execute Brain****: Difference between revisions
→{{header|Java}}
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Line 3,578:
[[/Java|Implementation in Java]].
import java.io.IOException;
public class Interpreter {
public final static int MEMORY_SIZE = 65536;
private final char[] memory = new char[MEMORY_SIZE];
private int dp;
private int ip;
private int border;
private void reset() {
for (int i = 0; i < MEMORY_SIZE; i++) {
memory[i] = 0;
}
ip = 0;
dp = 0;
}
private void load(String program) {
if (program.length() > MEMORY_SIZE - 2) {
throw new RuntimeException("Not enough memory.");
}
reset();
for (; dp < program.length(); dp++) {
memory[dp] = program.charAt(dp);
}
// memory[border] = 0 marks the end of instructions. dp (data pointer) cannot move lower than the
// border into the program area.
border = dp;
dp += 1;
}
public void execute(String program) {
load(program);
char instruction = memory[ip];
while (instruction != 0) {
switch (instruction) {
case '>':
dp++;
if (dp == MEMORY_SIZE) {
throw new RuntimeException("Out of memory.");
}
break;
case '<':
dp--;
if (dp == border) {
throw new RuntimeException("Invalid data pointer.");
}
break;
case '+':
memory[dp]++;
break;
case '-':
memory[dp]--;
break;
case '.':
System.out.print(memory[dp]);
break;
case ',':
try {
// Only works for one byte characters.
memory[dp] = (char) System.in.read();
} catch (IOException e) {
throw new RuntimeException(e);
}
break;
case '[':
if (memory[dp] == 0) {
skipLoop();
}
break;
case ']':
if (memory[dp] != 0) {
loop();
}
break;
default:
throw new RuntimeException("Unknown instruction.");
}
instruction = memory[++ip];
}
}
private void skipLoop() {
int loopCount = 0;
while (memory[ip] != 0) {
if (memory[ip] == '[') {
loopCount++;
} else if (memory[ip] == ']') {
loopCount--;
if (loopCount == 0) {
return;
}
}
ip++;
}
if (memory[ip] == 0) {
throw new RuntimeException("Unable to find a matching ']'.");
}
}
private void loop() {
int loopCount = 0;
while (ip >= 0) {
if (memory[ip] == ']') {
loopCount++;
} else if (memory[ip] == '[') {
loopCount--;
if (loopCount == 0) {
return;
}
}
ip--;
}
if (ip == -1) {
throw new RuntimeException("Unable to find a matching '['.");
}
}
public static void main(String[] args) {
Interpreter interpreter = new Interpreter();
interpreter.execute(">++++++++[-<+++++++++>]<.>>+>-[+]++>++>+++[>[->+++<<+++>]<<]>-----.>->+++..+++.>-.<<+[>[+>+]>>]<--------------.>>.+++.------.--------.>+.>+.");
}
}
=={{header|JavaScript}}==
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