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| <h4 class="subsection">3.10.1 Misnesting</h4> |
| |
| <p>When a macro is called with arguments, the arguments are substituted |
| into the macro body and the result is checked, together with the rest of |
| the input file, for more macro calls. It is possible to piece together |
| a macro call coming partially from the macro body and partially from the |
| arguments. For example, |
| |
| <pre class="smallexample"> #define twice(x) (2*(x)) |
| #define call_with_1(x) x(1) |
| call_with_1 (twice) |
| ==> twice(1) |
| ==> (2*(1)) |
| </pre> |
| <p>Macro definitions do not have to have balanced parentheses. By writing |
| an unbalanced open parenthesis in a macro body, it is possible to create |
| a macro call that begins inside the macro body but ends outside of it. |
| For example, |
| |
| <pre class="smallexample"> #define strange(file) fprintf (file, "%s %d", |
| ... |
| strange(stderr) p, 35) |
| ==> fprintf (stderr, "%s %d", p, 35) |
| </pre> |
| <p>The ability to piece together a macro call can be useful, but the use of |
| unbalanced open parentheses in a macro body is just confusing, and |
| should be avoided. |
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