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Macro LOOP

Syntax

  • The "simple" loop form:
    • loop compound-form*result*
  • The "extended" loop form:
    • loop [name-clause] {variable-clause}* {main-clause}*result*

name-clause ::= named name variable-clause ::= with-clause | initial-final | for-as-clause with-clause ::= with var1 [type-spec] [= form1] {and var2 [type-spec] [= form2]}* main-clause ::= unconditional | accumulation | conditional | termination-test | initial-final initial-final ::= initially compound-form+ | finally compound-form+ unconditional ::= {do | doing} compound-form+ | return {form | it} accumulation ::= list-accumulation | numeric-accumulation list-accumulation ::= {collect | collecting | append | appending | nconc | nconcing} {form | it} [into simple-var] numeric-accumulation ::= {count | counting | sum | summing | maximize | maximizing | minimize | minimizing} {form | it} [into simple-var] [type-spec] conditional ::= {if | when | unless} form selectable-clause {and selectable-clause}* [else selectable-clause {and selectable-clause}*] [end] selectable-clause ::= unconditional | accumulation | conditional termination-test ::= while form | until form | repeat form | always form | never form | thereis form for-as-clause ::= {for | as} for-as-subclause {and for-as-subclause}* for-as-subclause ::= for-as-arithmetic | for-as-in-list | for-as-on-list | for-as-equals-then |for-as-across | for-as-hash | for-as-package for-as-arithmetic ::= var [type-spec] for-as-arithmetic-subclause for-as-arithmetic-subclause ::= arithmetic-up | arithmetic-downto | arithmetic-downfrom arithmetic-up ::= ⟦{from | upfrom} form1 | {to | upto | below} form2 | form3+ arithmetic-downto ::= ⟦ {from form1}1 | {{downto | above} form2}1 | form3 ⟧ arithmetic-downfrom ::= ⟦ {downfrom form1}1 | {to | downto | above} form2 | form3 ⟧ for-as-in-list ::= var [type-spec] in form1 [by step-fun] for-as-on-list ::= var [type-spec] on form1 [by step-fun] for-as-equals-then ::= var [type-spec] = form1 [then form2] for-as-across ::= var [type-spec] across vector for-as-hash ::= var [type-spec] being {each | the} {{hash-key | hash-keys} {in | of} hash-table [using (hash-value other-var)] | {hash-value | hash-values} {in | of} hash-table [using (hash-key other-var)]} for-as-package ::= var [type-spec] being {each | the} {symbol | symbols | present-symbol | present-symbols | external-symbol | external-symbols} [{in | of} package] type-spec ::= simple-type-spec | destructured-type-spec simple-type-spec ::= fixnum | float | t | nil destructured-type-spec ::= of-type d-type-spec d-type-spec ::= type-specifier | (d-type-spec . d-type-spec) var ::= d-var-spec var1 ::= d-var-spec var2 ::= d-var-spec other-var ::= d-var-spec d-var-spec ::= simple-var | nil | (d-var-spec . d-var-spec)

Arguments and Values

Description

For details, see section {\secref\LoopFacility}.

Examples

An example of the simple form of loop.

(defun sqrt-advisor () (loop (format t "~&Number: ") (let ((n (parse-integer (read-line) :junk-allowed t))) (when (not n) (return)) (format t "~&The square root of ~D is ~D.~%" n (sqrt n)))))

SQRT-ADVISOR

(sqrt-advisor)

Number: 5 The square root of 5 is 2.236068. Number: 4 The square root of 4 is 2. Number: done

NIL

Two examples of the extended form of LOOP.

(defun square-advisor () (loop as n = (progn (format t "~&Number: ") (parse-integer (read-line) :junk-allowed t)) while n do (format t "~&The square of ~D is ~D.~%" n (* n n))))

SQUARE-ADVISOR

(square-advisor)

Number: 4 The square of 4 is 16. Number: 23 The square of 23 is 529. Number: done

NIL

(loop for n from 1 to 10 when (oddp n) collect n)

(1 3 5 7 9)

Affected By

None.

Exceptional Situations

None.

See Also

Notes

Except that loop-finish cannot be used within a simple loop form, a simple loop form is related to an extended loop form in the following way:

(loop compound-form*) ≡ (loop do compound-form*)

\issue{LOOP-SYNTAX-OVERHAUL:REPAIR} \issue{LOOP-MISCELLANEOUS-REPAIRS:FIX}