Documentation
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Overview ¶
Package arithmetic evaluates the arithmetic a configuration keyword holds, so a size can be written as a share of another size rather than as a number somebody worked out by hand.
size = $(50% * {disk#vg.capacity})
size = $({DEFAULT.size} / 2)
size = $({disk#vg.capacity} - 10g)
The references are resolved before this is asked anything, so what it reads is arithmetic over numbers. A number is written the way every other size in a configuration is written, so "10g" and "10GB" are sizes here too.
The operators are "+", "-", "*", "/", "//" and "%". The last two are the integer division and the remainder of it, so "5//2" is 2 and "5%2" is 1.
A percent sign is also how a share is written, "50%" being a half, and the two are told apart by what follows the sign: a number opens the right side of a remainder, and anything else ends a share. So "50% * 10g" is half of ten gibibytes, and "50 % 2" is what is left of fifty when divided by two.
Index ¶
Constants ¶
const Open = "$("
Open is what introduces an expression, and is looked for before anything else is done, so a value holding none is not parsed at all.
Variables ¶
This section is empty.
Functions ¶
func Eval ¶
Eval replaces every expression in s by the number it computes, and leaves the rest of s alone.
func EvalExpr ¶
EvalExpr computes one expression, written without the "$(" and ")" around it.
The arithmetic is done in floating point and the answer rounded, because a share of a size is a fraction and the caller is asking for a count of bytes: a half of an odd number of them is one of them or the other, not an error.
Types ¶
This section is empty.
Source Files