Rosetta Code

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

Page Discussion

Execute Brain****/Java (view source)

Revision as of 00:11, 8 March 2008

136 bytes removed ,  16 years ago
m
Added syntax highlighting and now it looks all cool
m (Optimized a bit on loops)
m (Added syntax highlighting and now it looks all cool)
Line 10:
More detailed information about the rest of the code can be found in the comments throughout it.<br clear=all>
 
<java>import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
 
▼
/**
* Interprets Brainf**k source from std in or a file.
*
* @author Mike Neurohr
*/
public class BF{
private static int pointer;//memory pointer
private static int codeIndex;//instruction number
private static final int INITIAL_SIZE= 1000;//initial size of memory
private static final String instChars= "[]<>,.+-";//valid code characters
 
▼
/**
* The main program. Holds the input loop and error-handling.
*
* @param args 0: Source file others: ignored
*/
public static void main(String[] args){
BufferedReader source;
try{
if(args.length == 0){//if no file specified
source= new BufferedReader(new InputStreamReader(System.in));
}else{
source= new BufferedReader(new FileReader(args[0]));
}
char instruction;
 
▼
//holds the cleaned up code
StringBuilder code= new StringBuilder();
 
//count for loop syntax errors
int bCnt= 0;
 
//read whole source in
for(instruction= (char)source.read(); source.ready(); instruction=
(char)source.read()){
//remove extra characters
if(instChars.contains(instruction + "")){
//add the instruction to the clean code
code.append(instruction);
if(instruction == '[') bCnt++;
if(instruction == ']') bCnt--;
}
}
if(bCnt != 0){//if there is a bracket with no match
System.err.println("Error: Uneven brackets.");
return;
}
 
//set up input for ,
BufferedReader input=
new BufferedReader(new InputStreamReader(System.in));
//set up memory
ArrayList<Integer> memory= new ArrayList<Integer>(INITIAL_SIZE);
memory.add(new Integer(0));
pointer= 0; //initialize pointer
//loop through the cleaned up code and execute
for(codeIndex= 0;codeIndex < code.length();codeIndex++){
instruction= code.charAt(codeIndex);
switch(instruction){
case '+':
memory.set(pointer, memory.get(pointer) + 1);
break;
case '-':
memory.set(pointer, memory.get(pointer) - 1);
break;
case '.':
System.out.print((char)memory.get(pointer).intValue());
break;
case ',':
input(memory, input);
break;
case '[':
if(memory.get(pointer) == 0){
//skip the code inside the loop
jumpForward(code);
}
//if the loop can continue...
//we don't need to check other things
break;
case ']':
if(memory.get(pointer) != 0){
//go back to the corresponding [ to check
jumpBack(code);
}
//if the loop should stop...
//we don't need to check other things
break;
case '>':
pointer++;
//gets rid of NullPointerExceptions
while(pointer + 1 > memory.size()) memory.add(0);
break;
case '<':
if(--pointer < 0){
//can't do it
System.err.println("Pointer out of range (negative).");
return;
}
default:
}
}
}catch(FileNotFoundException e){
System.err.println("Error opening file: " + args[0] + ".");
}catch(IOException e){
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));
}
}
Anonymous user
Retrieved from "https://rosettacode.org/wiki/Special:MobileDiff/47484"