| 494 | | |
| | 494 | === Macros === |
| | 495 | Remember to put always the parameters between parentheses, so that maybe the parameter needs to be calculated before to use it, just like: |
| | 496 | {{{ |
| | 497 | #!C |
| | 498 | #define MAX(a,b) ((a) > (b) ? (a) : (b)) |
| | 499 | |
| | 500 | result = 2 * MAX( x, y & 0xFF ); |
| | 501 | }}} |
| | 502 | |
| | 503 | ==== The # Operator ==== |
| | 504 | When used inside a macro, it is replaced by the parameter given to the macro call, so: |
| | 505 | {{{ |
| | 506 | #!C |
| | 507 | #define impr(i) printf( "value " #i " = %d", i) |
| | 508 | |
| | 509 | int x = 18, y = 2; |
| | 510 | impr(x-y); |
| | 511 | // result: "value x-y = 16" |
| | 512 | }}} |
| | 513 | |
| | 514 | ==== The ## Operator ==== |
| | 515 | When used inside a macro, it is replaced by the parameters given to the macro and removing spaces, so: |
| | 516 | {{{ |
| | 517 | #!C |
| | 518 | #define impr(i) printf( #var " with " #num " = %d" var ## num ) |
| | 519 | // var ## num (x and 5) is replaced by x5 |
| | 520 | |
| | 521 | int x4 = 15, x5 = 16; |
| | 522 | impr( x, 5 ); |
| | 523 | // result: "x with 5 = 16" |
| | 524 | }}} |
| | 525 | |
| | 526 | |
| | 527 | ==== #include, #if, #else, #elif, #endif ==== |
| | 528 | {{{ |
| | 529 | #!C |
| | 530 | #if VERSION == 1 |
| | 531 | #define MY_PROJ "version1.h" |
| | 532 | #else |
| | 533 | #define MY_PROJ "version2.h" |
| | 534 | #endif |
| | 535 | |
| | 536 | #include MY_PROJ |
| | 537 | }}} |
| | 538 | |
| | 539 | |
| | 540 | ==== #ifdef, #ifndef, #undef ==== |
| | 541 | {{{ |
| | 542 | #!C |
| | 543 | #define MAX(a,b) ((a) > (b) ? (a) : (b)) |
| | 544 | |
| | 545 | #ifdef MAX |
| | 546 | #undef MAX |
| | 547 | #endif |