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XTRAN Demonstration:  Match and Replace C Expressions

In the rules below:

• this     indicates C pattern elements
• <this> indicates meta pattern elements

Note that XTRAN automatically applies the rules below recursively to every expression in the code being re-engineered.

The following rules effectively convert infix expression notation to prefix notation.

 XTRAN rules:

  Original C code:

     a = b + (c - d) * (e - f) / g;

 Resulting C code:

     copy(&a, add(b, div(mul(sub(c, d), sub(e, f)), g)));

In the following rules, the match of a "wildcard" pattern element is conditionalized with a Boolean expression; if the condition evaluates to false, the match fails at that element.

 XTRAN rule:

 Original C code:

     copy(p_var1, *p_var2);
     copy(p_var3, var4);
     copy(p_var5, var6 + var7);
     copy(p_var8 + 3, var9);

 Resulting C code:

     copy(p_var1, *p_var2);
     *p_var3 = var4;
     copy(p_var5, var6 + var7);
     *(p_var8 + 3) = var9;

COPYRIGHT 2012; reproduction prohibited without permission.  Revised 2009-09-11

XTRAN is a trademark of Pennington Systems Incorporated.