Execute Brain****/Java: Difference between revisions

Content added Content deleted
m (Optimized a bit on loops)
m (Added syntax highlighting and now it looks all cool)
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More detailed information about the rest of the code can be found in the comments throughout it.<br clear=all>
More detailed information about the rest of the code can be found in the comments throughout it.<br clear=all>


import java.io.BufferedReader;
<java>import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.ArrayList;

⚫
/**
/**
* Interprets Brainf**k source from std in or a file.
* Interprets Brainf**k source from std in or a file.
*
*
* @author Mike Neurohr
* @author Mike Neurohr
*/
*/
public class BF{
public class BF{
private static int pointer;//memory pointer
private static int pointer;//memory pointer
private static int codeIndex;//instruction number
private static int codeIndex;//instruction number
private static final int INITIAL_SIZE= 1000;//initial size of memory
private static final int INITIAL_SIZE= 1000;//initial size of memory
private static final String instChars= "[]<>,.+-";//valid code characters
private static final String instChars= "[]<>,.+-";//valid code characters

⚫
/**
/**
* The main program. Holds the input loop and error-handling.
* The main program. Holds the input loop and error-handling.
*
*
* @param args 0: Source file others: ignored
* @param args 0: Source file others: ignored
*/
*/
public static void main(String[] args){
public static void main(String[] args){
BufferedReader source;
BufferedReader source;
try{
try{
if(args.length == 0){//if no file specified
if(args.length == 0){//if no file specified
source= new BufferedReader(new InputStreamReader(System.in));
source= new BufferedReader(new InputStreamReader(System.in));
}else{
}else{
source= new BufferedReader(new FileReader(args[0]));
source= new BufferedReader(new FileReader(args[0]));
}
}
char instruction;
char instruction;

⚫
//holds the cleaned up code
//holds the cleaned up code
StringBuilder code= new StringBuilder();
StringBuilder code= new StringBuilder();

//count for loop syntax errors
//count for loop syntax errors
int bCnt= 0;
int bCnt= 0;

//read whole source in
//read whole source in
for(instruction= (char)source.read(); source.ready(); instruction=
for(instruction= (char)source.read(); source.ready(); instruction=
(char)source.read()){
(char)source.read()){
//remove extra characters
//remove extra characters
if(instChars.contains(instruction + "")){
if(instChars.contains(instruction + "")){
//add the instruction to the clean code
//add the instruction to the clean code
code.append(instruction);
code.append(instruction);
if(instruction == '[') bCnt++;
if(instruction == '[') bCnt++;
if(instruction == ']') bCnt--;
if(instruction == ']') bCnt--;
}
}
}
}
if(bCnt != 0){//if there is a bracket with no match
if(bCnt != 0){//if there is a bracket with no match
System.err.println("Error: Uneven brackets.");
System.err.println("Error: Uneven brackets.");
return;
return;
}
}

//set up input for ,
//set up input for ,
BufferedReader input=
BufferedReader input=
new BufferedReader(new InputStreamReader(System.in));
new BufferedReader(new InputStreamReader(System.in));
//set up memory
//set up memory
ArrayList<Integer> memory= new ArrayList<Integer>(INITIAL_SIZE);
ArrayList<Integer> memory= new ArrayList<Integer>(INITIAL_SIZE);
memory.add(new Integer(0));
memory.add(new Integer(0));
pointer= 0; //initialize pointer
pointer= 0; //initialize pointer
//loop through the cleaned up code and execute
//loop through the cleaned up code and execute
for(codeIndex= 0;codeIndex < code.length();codeIndex++){
for(codeIndex= 0;codeIndex < code.length();codeIndex++){
instruction= code.charAt(codeIndex);
instruction= code.charAt(codeIndex);
switch(instruction){
switch(instruction){
case '+':
case '+':
memory.set(pointer, memory.get(pointer) + 1);
memory.set(pointer, memory.get(pointer) + 1);
break;
break;
case '-':
case '-':
memory.set(pointer, memory.get(pointer) - 1);
memory.set(pointer, memory.get(pointer) - 1);
break;
break;
case '.':
case '.':
System.out.print((char)memory.get(pointer).intValue());
System.out.print((char)memory.get(pointer).intValue());
break;
break;
case ',':
case ',':
input(memory, input);
input(memory, input);
break;
break;
case '[':
case '[':
if(memory.get(pointer) == 0){
if(memory.get(pointer) == 0){
//skip the code inside the loop
//skip the code inside the loop
jumpForward(code);
jumpForward(code);
}
}
//if the loop can continue...
//if the loop can continue...
//we don't need to check other things
//we don't need to check other things
break;
break;
case ']':
case ']':
if(memory.get(pointer) != 0){
if(memory.get(pointer) != 0){
//go back to the corresponding [ to check
//go back to the corresponding [ to check
jumpBack(code);
jumpBack(code);
}
}
//if the loop should stop...
//if the loop should stop...
//we don't need to check other things
//we don't need to check other things
break;
break;
case '>':
case '>':
pointer++;
pointer++;
//gets rid of NullPointerExceptions
//gets rid of NullPointerExceptions
while(pointer + 1 > memory.size()) memory.add(0);
while(pointer + 1 > memory.size()) memory.add(0);
break;
break;
case '<':
case '<':
if(--pointer < 0){
if(--pointer < 0){
//can't do it
//can't do it
System.err.println("Pointer out of range (negative).");
System.err.println("Pointer out of range (negative).");
return;
return;
}
}
default:
default:
}
}
}
}
}catch(FileNotFoundException e){
}catch(FileNotFoundException e){
System.err.println("Error opening file: " + args[0] + ".");
System.err.println("Error opening file: " + args[0] + ".");
}catch(IOException e){
}catch(IOException e){
System.err.println("Error on input.");
System.err.println("Error on input.");
}
}
⚫
}

⚫
public static void jumpBack(StringBuilder code){
⚫
//initial count for the bracket we're on
⚫
int bracketCnt= 1;
⚫
//count brackets until the corresponding [
⚫
while(codeIndex >= 0 && bracketCnt != 0){
⚫
codeIndex--;
⚫
char inst= code.charAt(codeIndex);
⚫
if(inst == '[') bracketCnt--;
⚫
if(inst == ']') bracketCnt++;
⚫
}
⚫
//"- 1" to offset the next "codeIndex++".
⚫
codeIndex= codeIndex - 1;
⚫
}

⚫
public static void jumpForward(StringBuilder code){
⚫
//initial count for the bracket we're on
⚫
int bracketCnt= 1;
⚫
//count brackets until the corresponding ]
⚫
while(codeIndex < code.length() && bracketCnt != 0){
⚫
codeIndex++;
⚫
char inst= code.charAt(codeIndex);
⚫
if(inst == ']') bracketCnt--;
⚫
if(inst == '[') bracketCnt++;
⚫
}
⚫
}

⚫
public static void input(ArrayList<Integer> mem, BufferedReader input)
⚫
throws IOException{
⚫
int val;
⚫
//read until something comes in other than return chars
⚫
for(val= input.read(); val == 10 || val == 13; val= input.read());
⚫
mem.set(pointer, new Integer(val));
}
}
}</java>
⚫
public static void jumpBack(StringBuilder code){
⚫
//initial count for the bracket we're on
⚫
int bracketCnt= 1;
⚫
//count brackets until the corresponding [
⚫
while(codeIndex >= 0 && bracketCnt != 0){
⚫
codeIndex--;
⚫
char inst= code.charAt(codeIndex);
⚫
if(inst == '[') bracketCnt--;
⚫
if(inst == ']') bracketCnt++;
⚫
}
⚫
//"- 1" to offset the next "codeIndex++".
⚫
codeIndex= codeIndex - 1;
}
⚫
public static void jumpForward(StringBuilder code){
⚫
//initial count for the bracket we're on
⚫
int bracketCnt= 1;
⚫
//count brackets until the corresponding ]
⚫
while(codeIndex < code.length() && bracketCnt != 0){
⚫
codeIndex++;
⚫
char inst= code.charAt(codeIndex);
⚫
if(inst == ']') bracketCnt--;
⚫
if(inst == '[') bracketCnt++;
⚫
}
}
⚫
public static void input(ArrayList<Integer> mem, BufferedReader input)
⚫
throws IOException{
⚫
int val;
⚫
//read until something comes in other than return chars
⚫
for(val= input.read(); val == 10 || val == 13; val= input.read());
⚫
mem.set(pointer, new Integer(val));
}
}
Retrieved from "https://rosettacode.org/wiki/Execute_Brain****/Java"