sig lpbasic_absyn.
%  higher-order abstract syntax and execution of lpbasic

kind lbexp type.    % lpbasic expressions
kind lbst type.     % lpbasic statements  (strings will represent types)
kind lbtype type.   % lpbasic types

type intexp int -> lbexp.
type strexp, varexp  string -> lbexp.
type sumexp, difexp, multexp, divexp, andexp, orexp  lbexp -> lbexp -> lbexp.
type eqexp, ineqexp   lbexp -> lbexp -> lbexp.
type notexp lbexp -> lbexp.
type printst lbexp -> lbst.
type assignst lbexp -> lbexp -> lbst.
type ifst lbexp -> lbst -> lbst.
type ifelsest lbexp -> lbst -> lbst -> lbst.
type blockst (list lbst) -> lbst.
type whilest lbexp -> lbst -> lbst.
type letst lbexp -> (lbexp -> lbst) -> lbst.
type welltyped lbst -> o.
type hastype lbexp -> lbtype -> o.

type integer, ascii, boolean, void     lbtype.

% A program will be a (list lbst)

%  other predicate declarations:
type copyexp lbexp -> lbexp -> o.
type copyst lbst -> lbst -> o.
type lbeval lbexp -> lbexp -> o.
type lbexecute (list lbst) -> o.
type bind lbexp -> lbexp -> o.  % variable bindings  (not used)
type formlet lbst -> lbst -> lbst -> o.
type printit lbexp -> o.
type process_string string -> string -> o.
type run string -> o.
type appendd (list A) -> (list A) -> (list A) -> o.