three address code generation program in java
/*
Program to implement Three Address Code in Java
Author: Surajit Karmakar Author Link: https://www.facebook.com/surajit.3528
www.pracspedia.com
*/
import java.io.*;
class ThreeAddressCode
{
private static final char[][] precedence = {
{'/', '1'},
{'*', '1'},
{'+', '2'},
{'-', '2'}
};
private static int precedenceOf(String t)
{
char token = t.charAt(0);
for (int i=0; i < precedence.length; i++)
{
if (token == precedence[i][0])
{
return Integer.parseInt(precedence[i][1]+"");
}
}
return -1;
}
public static void main(String[] args) throws Exception
{
int i, j, opc=0;
char token;
boolean processed[];
String[][] operators = new String[10][2];
String expr="", temp;
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
System.out.print("\nEnter an expression: ");
expr = in.readLine();
processed = new boolean[expr.length()];
for (i=0; i < processed.length; i++)
{
processed[i] = false;
}
for (i=0; i < expr.length(); i++)
{
token = expr.charAt(i);
for (j=0; j < precedence.length; j++)
{
if (token==precedence[j][0])
{
operators[opc][0] = token+"";
operators[opc][1] = i+"";
opc++;
break;
}
}
}
System.out.println("\nOperators:\nOperator\tLocation");
for (i=0; i < opc; i++)
{
System.out.println(operators[i][0] + "\t\t" + operators[i][1]);
}
//sort
for (i=opc-1; i >= 0; i--)
{
for (j=0; j < i; j++)
{
if (precedenceOf(operators[j][0]) > precedenceOf(operators[j+1][0]))
{
temp = operators[j][0];
operators[j][0] = operators[j+1][0];
operators[j+1][0] = temp;
temp = operators[j][1];
operators[j][1] = operators[j+1][1];
operators[j+1][1] = temp;
}
}
}
System.out.println("\nOperators sorted in their precedence:\nOperator\tLocation");
for (i=0; i < opc; i++)
{
System.out.println(operators[i][0] + "\t\t" + operators[i][1]);
}
System.out.println();
for (i=0; i < opc; i++)
{
j = Integer.parseInt(operators[i][1]+"");
String op1="", op2="";
if (processed[j-1]==true)
{
if (precedenceOf(operators[i-1][0]) == precedenceOf(operators[i][0]))
{
op1 = "t"+i;
}
else
{
for (int x=0; x < opc; x++)
{
if ((j-2) == Integer.parseInt(operators[x][1]))
{
op1 = "t"+(x+1)+"";
}
}
}
}
else
{
op1 = expr.charAt(j-1)+"";
}
if (processed[j+1]==true)
{
for (int x=0; x < opc; x++)
{
if ((j+2) == Integer.parseInt(operators[x][1]))
{
op2 = "t"+(x+1)+"";
}
}
}
else
{
op2 = expr.charAt(j+1)+"";
}
System.out.println("t"+(i+1)+" = "+op1+operators[i][0]+op2);
processed[j] = processed[j-1] = processed[j+1] = true;
}
}
}