.. _debugger-expressions-list: Debugger Expressions Guide ========================== Expressions can be used anywhere a numeric parameter is expected. The syntax for expressions is very close to standard C-style syntax with full operator ordering and parentheses. There are a few operators missing (notably the trinary ? : operator), and a few new ones (memory accessors). The table below lists all the operators in their order, highest precedence operators first. | | ( ) : standard parentheses | ++ -- : postfix increment/decrement | ++ -- ~ ! - + b@ w@ d@ q@ : prefix inc/dec, binary NOT, logical NOT, unary +/-, memory access | * / % : multiply, divide, modulus | + - : add, subtract | << >> : shift left/right | < <= > >= : less than, less than or equal, greater than, greater than or equal | == != : equal, not equal | & : binary AND | ^ : binary XOR | | : binary OR | && : logical AND | || : logical OR | = \*= /= %= += -= <<= >>= &= \|= ^= : assignment | , : separate terms, function parameters | | Numbers ------- Numbers are prefixed according to their bases: - Hexadecimal (base-16) numbers are prefixed with :code:`$` or :code:`0x`. - Decimal (base-10) numbers are prefixed with :code:`#`. - Octal (base-8) numbers are prefixed with :code:`0o`. - Binary (base-2) numbers are prefixed with :code:`0b`. - Unprefixed numbers are hexadecimal (base-16). Examples: - :code:`123` is 123 hexadecimal (291 decimal). - :code:`$123` is 123 hexadecimal (291 decimal). - :code:`0x123` is 123 hexadecimal (291 decimal). - :code:`#123` is 123 decimal. - :code:`0o123` is 123 octal (83 decimal). - :code:`0b1001` is 9 decimal. - :code:`0b123` is invalid. Differences from C Behaviors ---------------------------- - First, all math is performed on full 64-bit unsigned values, so things like **a < 0** won't work as expected. - Second, the logical operators **&&** and **||** do not have short-circuit properties -- both halves are always evaluated. - Finally, the new memory operators work like this: - **b!** refers to the byte at but does *NOT* suppress side effects such as reading a mailbox clearing the pending flag, or reading a FIFO removing an item. - **b@** refers to the byte at while suppressing side effects. - Similarly, **w@** and **w!** refer to a *word* in memory, **d@** and **d!** refer to a *dword* in memory, and **q@** and **q!** refer to a *qword* in memory. The memory operators can be used as both lvalues and rvalues, so you can write **b\@100 = ff** to store a byte in memory. By default these operators read from the program memory space, but you can override that by prefixing them with a 'd' or an 'i'. As such, **dw\@300** refers to data memory word at address 300 and **id\@400** refers to an I/O memory dword at address 400. dl/video.h?h=mame0162&id=10bee5ce7812d7faaecf238cf9570b802e02d56e'>blame)
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