An *integer expression* is one or more *arguments* delimited
by *operators*.

*Arguments* are symbols, numbers or subexpressions. In other
contexts arguments are sometimes called "arithmetic operands". In
this manual, to avoid confusing them with the "instruction operands" of
the machine language, we use the term "argument" to refer to parts of
expressions only, reserving the word "operand" to refer only to machine
instruction operands.

Symbols are evaluated to yield {`section` `NNN`} where
`section` is one of text, data, bss, absolute,
or undefined. `NNN` is a signed, 2's complement 32 bit
integer.

Numbers are usually integers.

A number can be a flonum or bignum. In this case, you are warned
that only the low order 32 bits are used, and `as` pretends
these 32 bits are an integer. You may write integer-manipulating
instructions that act on exotic constants, compatible with other
assemblers.

Subexpressions are a left parenthesis `(` followed by an integer
expression, followed by a right parenthesis `)`; or a prefix
operator followed by an argument.

*Operators* are arithmetic functions, like `+` or `%`. Prefix
operators are followed by an argument. Infix operators appear
between their arguments. Operators may be preceded and/or followed by
whitespace.

`as` has the following *prefix operators*. They each take
one argument, which must be absolute.

`-`*Negation*. Two's complement negation.`~`*Complementation*. Bitwise not.

*Infix operators* take two arguments, one on either side. Operators
have precedence, but operations with equal precedence are performed left
to right. Apart from `+` or `-`, both arguments must be
absolute, and the result is absolute.

Highest Precedence

`*`*Multiplication*.`/`*Division*. Truncation is the same as the C operator`/``%`*Remainder*.`<`,`<<`*Shift Left*. Same as the C operator`<<`.`>`,`>>`*Shift Right*. Same as the C operator`>>`.

Intermediate precedence

`|`*Bitwise Inclusive Or*.`&`*Bitwise And*.`^`*Bitwise Exclusive Or*.`!`*Bitwise Or Not*.

Low Precedence

`+`*Addition*. If either argument is absolute, the result has the section of the other argument. You may not add together arguments from different sections.`-`*Subtraction*. If the right argument is absolute, the result has the section of the left argument. If both arguments are in the same section, the result is absolute. You may not subtract arguments from different sections.`==`*Is Equal To*`<>`*Is Not Equal To*`<`*Is Less Than*`>`*Is Greater Than*`>=`*Is Greater Than Or Equal To*`<=`*Is Less Than Or Equal To*The comparison operators can be used as infix operators. A true results has a value of -1 whereas a false result has a value of 0. Note, these operators perform signed comparisons.

Lowest Precedence

`&&`*Logical And*.`||`*Logical Or*.These two logical operations can be used to combine the results of sub expressions. Note, unlike the comparison operators a true result returns a value of 1 but a false results does still return 0. Also note that the logical or operator has a slightly lower precedence than logical and.

In short, it's only meaningful to add or subtract the *offsets* in an
address; you can only have a defined section in one of the two arguments.