Er-progn
Perform a sequence of state-changing ``error triples''
Example:
(er-progn (check-good-foo-p (f-get-global 'my-foo state) state)
(value (* (f-get-global 'my-foo state)
(f-get-global 'bar state))))
This sequencing primitive is only useful when programming with state, something that very few users will probably want to do. See state.
Er-progn is used much the way that progn is used in Common
Lisp, except that it expects each form within it to evaluate to an error-triple of the form (mv erp val state). The first such form, if
any, that evaluates to such a triple where erp is not nil yields the
error triple returned by the er-progn. If there is no such form, then
the er-progn form returns the value of the last form.
General Form:
(er-progn <expr1> ... <exprk>)
where each <expri> is an expression that evaluates to an error triple
(see programming-with-state). The above form is essentially equivalent
to the following (``essentially'' because in fact, care is taken to avoid
variable capture).
(mv-let (erp val state)
<expr1>
(cond (erp (mv erp val state))
(t (mv-let (erp val state)
<expr2>
(cond (erp (mv erp val state))
(t ...
(mv-let (erp val state)
<expr{k-1}>
(cond (erp (mv erp val state))
(t <exprk>)))))))))
