LOOP — Extension to Common Lisp
Loop to iterate over all the
tuples of a query via a loop clause.Loop Clause
{as | for} var [type-spec] being {each | the} {record | records | tuple | tuples} {in | of} query [from database]varA d-var-spec, as defined in the
grammar for loop-clauses in the ANSI
Standard for Common Lisp. This allows for the usual
loop-style destructuring.
type-specAn optional type-spec either
simple or destructured, as defined in the grammar for
loop-clauses in the ANSI Standard for
Common Lisp.
queryAn sql
expression that represents an SQL
query which is expected to return a (possibly empty)
result set, where each tuple has as many attributes as
function takes arguments.
databaseAn optional database object. This will default to the value of *default-database*.
This clause is an iteration driver for
loop, that binds the given variable
(possibly destructured) to the consecutive tuples (which are
represented as lists of attribute values) in the result set
returned by executing the SQL query
expression on the database
specified.
query may be an object query (i.e., the
selection arguments refer to View Classes), in which case the
supplied variable is bound to the tuples of View Class
instances returned by the object oriented query.
(defvar *my-db* (connect '("dent" "newesim" "dent" "dent"))
"My database"
=> *MY-DB*
(loop with time-graph = (make-hash-table :test #'equal)
with event-graph = (make-hash-table :test #'equal)
for (time event) being the tuples of "select time,event from log"
from *my-db*
do
(incf (gethash time time-graph 0))
(incf (gethash event event-graph 0))
finally
(flet ((show-graph (k v) (format t "~40A => ~5D~%" k v)))
(format t "~&Time-Graph:~%===========~%")
(maphash #'show-graph time-graph)
(format t "~&~%Event-Graph:~%============~%")
(maphash #'show-graph event-graph))
(return (values time-graph event-graph)))
>> Time-Graph:
>> ===========
>> D => 53000
>> X => 3
>> test-me => 3000
>>
>> Event-Graph:
>> ============
>> CLOS Benchmark entry. => 9000
>> Demo Text... => 3
>> doit-text => 3000
>> C Benchmark entry. => 12000
>> CLOS Benchmark entry => 32000
=> #<EQUAL hash table, 3 entries {48350A1D}>
=> #<EQUAL hash table, 5 entries {48350FCD}>
(loop for (forename surname)
being each tuple in
[select [first-name] [last-name] :from [employee]
:order-by [last-name]]
collect (concatenate 'string forename " " surname))
=> ("Yuri Andropov" "Leonid Brezhnev" "Konstantin Chernenko" "Mikhail Gorbachev"
"Nikita Kruschev" "Vladimir Lenin" "Vladimir Putin" "Josef Stalin"
"Leon Trotsky" "Boris Yeltsin")
(loop for (e) being the records in
[select 'employee :where [< [emplid] 4] :order-by [emplid]]
collect (slot-value e 'last-name))
=> ("Lenin" "Stalin" "Trotsky")