►Dracula: Reference Manual
▼1 ACL2
►1.6 ACL2 Books
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1.6.1 "data-structures/ list-theory"
deflist
1.6.2 "data-structures/ structures"
defstructure
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1.6 ACL2 Books

1.6.1 "data-structures/list-theory"

(include-book "data-structures/list-theory" :dir :system)
(deflist <list-pred> (l) <pred>)
Dracula supports the deflist form for defining new list types from the "data-structures/list-theory" book. It defines the predicate <list-pred>, recognizing lists whose elements satisfy <pred>. The (l) identifies the list as the predicate’s only parameter; ACL2 supports other parameter lists but Dracula currently does not.

Examples:

  > (deflist even-listp (l) evenp)

  eval:1:0: defun: defined outside of begin-below at: HERE

  in: (defun even-listp (l) (cond ((null? l) (quote t))

  ((pair? l) (if (not (member (evenp (car l)) (quote (nil

  ())))) (even-listp (cdr l)) (quote ()))) (else (quote ()))))

  > (even-listp (list 2 4 6))

  eval:2:0: application: bad syntax in: (top/error .

  even-listp)

  > (even-listp (list 1 3 5))

  eval:3:0: application: bad syntax in: (top/error .

  even-listp)

  > (even-listp 'not-a-list)

  eval:4:0: application: bad syntax in: (top/error .

  even-listp)

1.6.2 "data-structures/structures"

(include-book "data-structures/structures" :dir :system)
(defstructure <name> field ...)
 
field = <field-name>
  | (<field-name> (:assert <guard-expr>))
Dracula supports the defstructure form for defining new structure types from the "data-structures/structures" book. It defines a constructor <name>, a predicate <name>-p a weak predicate weak-<name>-p, and a selector <name>-<field-name> for each field, with optional guards for the structure and each field which are incorporated into the predicate (but not the weak predicate).

Examples:

  > (defstructure circle radius)

  mutual-recursion: defined outside of begin-below at: HERE

  in: (mutual-recursion (defun circle (radius2) (circle3

  radius2)) (defun weak-circle-p (x) (weak-circle-p4 x))

  (defun circle-p (x) (circle-p5 x)) (defun circle-radius (x)

  (circle-radius7 x)))

  > (circle 10)

  eval:6:0: application: bad syntax in: (top/error . circle)

  > (circle-radius (circle 10))

  eval:7:0: application: bad syntax in: (top/error .

  circle-radius)

  > (circle-p (circle 10))

  eval:8:0: application: bad syntax in: (top/error . circle-p)

  > (circle-p 'not-a-circle)

  eval:9:0: application: bad syntax in: (top/error . circle-p)

  > (defstructure rect
      (width (:assert (natp width)))
      (height (:assert (natp height))))

  mutual-recursion: defined outside of begin-below at: HERE

  in: (mutual-recursion (defun rect (temp16 temp17) (rect18

  temp16 temp17)) (defun weak-rect-p (x) (weak-rect-p19 x))

  (defun rect-p (x) (rect-p20 x)) (defun rect-width (x)

  (rect-width22 x)) (defun rect-height (x) (rect-height23 x)))

  > (rect 10 20)

  eval:11:0: application: bad syntax in: (top/error . rect)

  > (rect-width (rect 10 20))

  eval:12:0: application: bad syntax in: (top/error .

  rect-width)

  > (rect-height (rect 10 20))

  eval:13:0: application: bad syntax in: (top/error .

  rect-height)

  > (rect-p (rect 10 20))

  eval:14:0: application: bad syntax in: (top/error . rect-p)

  > (rect-p (rect -10 -20))

  eval:15:0: application: bad syntax in: (top/error . rect-p)

  > (rect-p 'not-a-rect)

  eval:16:0: application: bad syntax in: (top/error . rect-p)

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