-- this is the file EVALUATE.ADs 12:18PM  10/31/95
-- It contains the def of the package Evaluate, containing
-- eval and apply (and auxiliary subprograms) and the driver
-- procedure to use as a read-eval-print loop
-- The type Exp (expression) is defined in package expr, get and 
-- put for expressions are defined in package expr.io. Evaluation
-- environments, defined in package evalenv, are implemented as 
-- stacks of frames (each a symbol table).
 

with text_io, expr, evalenv;
use text_io, expr, evalenv;
package evaluate is

Input, Output : File_type; 

eval_called_on_endparen, eval_called_on_exit, 
EnvOverflow, unknown_primitive : exception;

procedure Eval(Ex:in Exp; En:in out Env; ExpVal: in out Exp);
procedure Apply(Opr: in Exp; Actuals: in ExpList; En: in out Env;
                             ExpVal: in out Exp);

procedure Driver;

end evaluate;