1.3 Logic Conditions

‘pmccabe’ does not score logic conditions very well. It overcharges for simple logical operations, it doesn’t charge for comma operators, and it undercharges for mixing assignment operators and relational operators and the and and or logical operators.

For example:

xx = (A && B) || (C && D) || (E && F);

scores as 6. Strictly speaking, there are, indeed, six code paths there. That is a fairly straight forward expression that is not nearly as complicated as this:

  if (A) {
    if (B) {
      if (C) {
        if (D)
          a-b-c-and-d;
      } else if (E) {
          a-b-no_c-and-e;
      }
    }
  }

and yet this scores exactly the same. This program reduces the cost to very little for a sequence of conditions at the same level. (That is, all and operators or all or operators.) so the raw score for these examples are 4 and 35, respectively (1 and 2 after scaling, see section --scale).

If you nest boolean expressions, there is a little cost, assuming you parenthesize grouped expressions so that and and or operators do not appear at the same parenthesized level. Also assuming that you do not mix assignment and relational and boolean operators all together. If you do not parenthesize these into subexpressions, their small scores get multiplied in ways that sometimes wind up as a much higher score.

The intent here is to encourage easy to understand boolean expressions. This is done by,

• not combining them with assignment statements
• canonicalizing them (two level expressions with all && operators at the bottom level and all || operators in the nested level -\- or vice versa)
• parenthesizing for visual clarity (relational operations parenthesized before being joined into larger && or || expressions)
• breaking them up into multiple if statements, if convenient.

This document was generated by Bruce Korb on May 15, 2011 using texi2html 1.82.