Dragon

This is a C# front-end parser derived from the Dragon book, found in Appendix A.

Aho, Alfred V., and Alfred V. Aho. Compilers: Principles, Techniques, & Tools. Boston: Pearson/Addison Wesley, 2007. Print. Amazon.com

This takes an input file and parses it into a syntax tree. The syntax tree can then be used to generate code in a different language. For example, the following code in the Dragon language:

{
   int i; int j; float v; float x; float[100] a;
   while(true) {
      do i = i+1; while( a[i] < v);
      do j = j-1; while( a[j] > v);
      if (i >= j) break;
      x = a[i]; a[i] = a[j]; a[j] = x;
   }
}

Produces the follwoing assembly level code:

L1:
L3:
        i = i + 1
L5:
        t1 = i * 8
        t2 = a [ t1 ]
        if t2 < v goto L3
L4:
        j = j - 1
L7:
        t3 = j * 8
        t4 = a [ t3 ]
        if t4 > v goto L4
L6:
        iffalse i >= j goto L8
L9:
        goto L2
L8:
        t5 = i * 8
        x = a [ t5 ]
L10:
        t6 = i * 8
        t7 = j * 8
        t8 = a [ t7 ]
        a [ t6 ] = t8
L11:
        t9 = j * 8
        a [ t9 ] = x
        goto L1
L2: