_at_.html -- ACL2 Version 6.3

### @

get the value of a global variable in `state`

    Major Section:  ACL2-BUILT-INS

    Examples:
    (+ (@ y) 1)
    (assign a (aset1 'ascii-map-array (@ a) 66 'Upper-case-B))

    General Form:
    (@ symbol)

where `symbol` is any symbol to which you have `assign`ed a global value. This macro expands into `(f-get-global 'symbol state)`, which retrieves the stored value of the symbol.

The macro `f-get-global` is closely related to `@`: `(@ var)` macroexpands to `(f-get-global 'var state)`.

The macro `assign` makes it convenient to set the value of a symbol. The `:``ubt` operation has no effect on the `global-table` of `state`. Thus, you may use these globals to hang onto useful data structures even though you may undo back past where you computed and saved them.