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Clean up cars and cdrs of -nth-item functions

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* dash.el (-first-item, -second-item, -third-item, -fifth-item):
Declare as pure and side-effect-free.
(-fourth-item): Ditto.  Define as alias of cadddr in newer Emacsen.
(-last-item): Mention -first-item in docstring.

* dev/examples.el (-first-item, -second-item, -third-item)
(-fourth-item, -fifth-item, -last-item): Extend tests.

* README.md:
* dash.texi: Regenerate docs.
master
Basil L. Contovounesios 4 years ago
parent 76606f9077
commit 4ac77a1017
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4 changed files with 121 additions and 69 deletions
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  1. 38
      README.md
  2. 40
      dash.el
  3. 74
      dash.texi
  4. 38
      dev/examples.el

38
README.md
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@ -2095,11 +2095,11 @@ Return the last x in `list` where (`pred` x) is non-`nil`, else `nil`.
Return the first item of `list`, or `nil` on an empty list. Return the first item of `list`, or `nil` on an empty list.
See also: [`-second-item`](#-second-item-list), [`-last-item`](#-last-item-list). See also: [`-second-item`](#-second-item-list), [`-last-item`](#-last-item-list), etc.
```el ```el
(-first-item '(1 2 3)) ;; => 1 (-first-item ()) ;; => ()
(-first-item nil) ;; => nil (-first-item '(1 2 3 4 5)) ;; => 1
(let ((list (list 1 2 3))) (setf (-first-item list) 5) list) ;; => (5 2 3) (let ((list (list 1 2 3))) (setf (-first-item list) 5) list) ;; => (5 2 3)
``` ```
@ -2107,53 +2107,59 @@ See also: [`-second-item`](#-second-item-list), [`-last-item`](#-last-item-list)
Return the second item of `list`, or `nil` if `list` is too short. Return the second item of `list`, or `nil` if `list` is too short.
See also: [`-third-item`](#-third-item-list). See also: [`-first-item`](#-first-item-list), [`-third-item`](#-third-item-list), etc.
```el ```el
(-second-item '(1 2 3)) ;; => 2 (-second-item ()) ;; => ()
(-second-item nil) ;; => nil (-second-item '(1 2 3 4 5)) ;; => 2
(let ((list (list 1 2))) (setf (-second-item list) 5) list) ;; => (1 5)
``` ```
#### -third-item `(list)` #### -third-item `(list)`
Return the third item of `list`, or `nil` if `list` is too short. Return the third item of `list`, or `nil` if `list` is too short.
See also: [`-fourth-item`](#-fourth-item-list). See also: [`-second-item`](#-second-item-list), [`-fourth-item`](#-fourth-item-list), etc.
```el ```el
(-third-item '(1 2 3)) ;; => 3 (-third-item ()) ;; => ()
(-third-item nil) ;; => nil (-third-item '(1 2)) ;; => ()
(-third-item '(1 2 3 4 5)) ;; => 3
``` ```
#### -fourth-item `(list)` #### -fourth-item `(list)`
Return the fourth item of `list`, or `nil` if `list` is too short. Return the fourth item of `list`, or `nil` if `list` is too short.
See also: [`-fifth-item`](#-fifth-item-list). See also: [`-third-item`](#-third-item-list), [`-fifth-item`](#-fifth-item-list), etc.
```el ```el
(-fourth-item '(1 2 3 4)) ;; => 4 (-fourth-item ()) ;; => ()
(-fourth-item nil) ;; => nil (-fourth-item '(1 2 3)) ;; => ()
(-fourth-item '(1 2 3 4 5)) ;; => 4
``` ```
#### -fifth-item `(list)` #### -fifth-item `(list)`
Return the fifth item of `list`, or `nil` if `list` is too short. Return the fifth item of `list`, or `nil` if `list` is too short.
See also: [`-last-item`](#-last-item-list). See also: [`-fourth-item`](#-fourth-item-list), [`-last-item`](#-last-item-list), etc.
```el ```el
(-fifth-item ()) ;; => ()
(-fifth-item '(1 2 3 4)) ;; => ()
(-fifth-item '(1 2 3 4 5)) ;; => 5 (-fifth-item '(1 2 3 4 5)) ;; => 5
(-fifth-item nil) ;; => nil
``` ```
#### -last-item `(list)` #### -last-item `(list)`
Return the last item of `list`, or `nil` on an empty list. Return the last item of `list`, or `nil` on an empty list.
See also: [`-first-item`](#-first-item-list), etc.
```el ```el
(-last-item '(1 2 3)) ;; => 3 (-last-item ()) ;; => ()
(-last-item nil) ;; => nil (-last-item '(1 2 3 4 5)) ;; => 5
(let ((list (list 1 2 3))) (setf (-last-item list) 5) list) ;; => (1 2 5) (let ((list (list 1 2 3))) (setf (-last-item list) 5) list) ;; => (1 2 5)
``` ```

40
dash.el
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@ -929,10 +929,10 @@ This function's anaphoric counterpart is `--every'."
"Return the last x in LIST where (PRED x) is non-nil, else nil." "Return the last x in LIST where (PRED x) is non-nil, else nil."
(--last (funcall pred it) list)) (--last (funcall pred it) list))
(defalias '-first-item 'car (defalias '-first-item #'car
"Return the first item of LIST, or nil on an empty list. "Return the first item of LIST, or nil on an empty list.
See also: `-second-item', `-last-item'. See also: `-second-item', `-last-item', etc.
\(fn LIST)") \(fn LIST)")
@ -940,40 +940,56 @@ See also: `-second-item', `-last-item'.
;; just like `car'. ;; just like `car'.
(put '-first-item 'byte-opcode 'byte-car) (put '-first-item 'byte-opcode 'byte-car)
(put '-first-item 'byte-compile 'byte-compile-one-arg) (put '-first-item 'byte-compile 'byte-compile-one-arg)
(put '-first-item 'pure t)
(put '-first-item 'side-effect-free t)
(defalias '-second-item 'cadr (defalias '-second-item #'cadr
"Return the second item of LIST, or nil if LIST is too short. "Return the second item of LIST, or nil if LIST is too short.
See also: `-third-item'. See also: `-first-item', `-third-item', etc.
\(fn LIST)") \(fn LIST)")
(put '-second-item 'pure t)
(put '-second-item 'side-effect-free t)
(defalias '-third-item (defalias '-third-item
(if (fboundp 'caddr) (if (fboundp 'caddr)
#'caddr #'caddr
(lambda (list) (car (cddr list)))) (lambda (list) (car (cddr list))))
"Return the third item of LIST, or nil if LIST is too short. "Return the third item of LIST, or nil if LIST is too short.
See also: `-fourth-item'. See also: `-second-item', `-fourth-item', etc.
\(fn LIST)") \(fn LIST)")
(defun -fourth-item (list) (put '-third-item 'pure t)
(put '-third-item 'side-effect-free t)
(defalias '-fourth-item
(if (fboundp 'cadddr)
#'cadddr
(lambda (list) (cadr (cddr list))))
"Return the fourth item of LIST, or nil if LIST is too short. "Return the fourth item of LIST, or nil if LIST is too short.
See also: `-fifth-item'." See also: `-third-item', `-fifth-item', etc.
(declare (pure t) (side-effect-free t))
(car (cdr (cdr (cdr list))))) \(fn LIST)")
(put '-fourth-item 'pure t)
(put '-fourth-item 'side-effect-free t)
(defun -fifth-item (list) (defun -fifth-item (list)
"Return the fifth item of LIST, or nil if LIST is too short. "Return the fifth item of LIST, or nil if LIST is too short.
See also: `-last-item'." See also: `-fourth-item', `-last-item', etc."
(declare (pure t) (side-effect-free t)) (declare (pure t) (side-effect-free t))
(car (cdr (cdr (cdr (cdr list)))))) (car (cddr (cddr list))))
(defun -last-item (list) (defun -last-item (list)
"Return the last item of LIST, or nil on an empty list." "Return the last item of LIST, or nil on an empty list.
See also: `-first-item', etc."
(declare (pure t) (side-effect-free t)) (declare (pure t) (side-effect-free t))
(car (last list))) (car (last list)))

74
dash.texi
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@ -3118,16 +3118,16 @@ Return the last x in @var{list} where (@var{pred} x) is non-@code{nil}, else @co
@defun -first-item (list) @defun -first-item (list)
Return the first item of @var{list}, or @code{nil} on an empty list. Return the first item of @var{list}, or @code{nil} on an empty list.
See also: @code{-second-item} (@pxref{-second-item}), @code{-last-item} (@pxref{-last-item}). See also: @code{-second-item} (@pxref{-second-item}), @code{-last-item} (@pxref{-last-item}), etc.
@example @example
@group @group
(-first-item '(1 2 3)) (-first-item ())
@result{} 1 @result{} ()
@end group @end group
@group @group
(-first-item nil) (-first-item '(1 2 3 4 5))
@result{} nil @result{} 1
@end group @end group
@group @group
(let ((list (list 1 2 3))) (setf (-first-item list) 5) list) (let ((list (list 1 2 3))) (setf (-first-item list) 5) list)
@ -3140,16 +3140,20 @@ See also: @code{-second-item} (@pxref{-second-item}), @code{-last-item} (@pxref{
@defun -second-item (list) @defun -second-item (list)
Return the second item of @var{list}, or @code{nil} if @var{list} is too short. Return the second item of @var{list}, or @code{nil} if @var{list} is too short.
See also: @code{-third-item} (@pxref{-third-item}). See also: @code{-first-item} (@pxref{-first-item}), @code{-third-item} (@pxref{-third-item}), etc.
@example @example
@group @group
(-second-item '(1 2 3)) (-second-item ())
@result{} ()
@end group
@group
(-second-item '(1 2 3 4 5))
@result{} 2 @result{} 2
@end group @end group
@group @group
(-second-item nil) (let ((list (list 1 2))) (setf (-second-item list) 5) list)
@result{} nil @result{} (1 5)
@end group @end group
@end example @end example
@end defun @end defun
@ -3158,16 +3162,20 @@ See also: @code{-third-item} (@pxref{-third-item}).
@defun -third-item (list) @defun -third-item (list)
Return the third item of @var{list}, or @code{nil} if @var{list} is too short. Return the third item of @var{list}, or @code{nil} if @var{list} is too short.
See also: @code{-fourth-item} (@pxref{-fourth-item}). See also: @code{-second-item} (@pxref{-second-item}), @code{-fourth-item} (@pxref{-fourth-item}), etc.
@example @example
@group @group
(-third-item '(1 2 3)) (-third-item ())
@result{} 3 @result{} ()
@end group @end group
@group @group
(-third-item nil) (-third-item '(1 2))
@result{} nil @result{} ()
@end group
@group
(-third-item '(1 2 3 4 5))
@result{} 3
@end group @end group
@end example @end example
@end defun @end defun
@ -3176,16 +3184,20 @@ See also: @code{-fourth-item} (@pxref{-fourth-item}).
@defun -fourth-item (list) @defun -fourth-item (list)
Return the fourth item of @var{list}, or @code{nil} if @var{list} is too short. Return the fourth item of @var{list}, or @code{nil} if @var{list} is too short.
See also: @code{-fifth-item} (@pxref{-fifth-item}). See also: @code{-third-item} (@pxref{-third-item}), @code{-fifth-item} (@pxref{-fifth-item}), etc.
@example @example
@group @group
(-fourth-item '(1 2 3 4)) (-fourth-item ())
@result{} 4 @result{} ()
@end group @end group
@group @group
(-fourth-item nil) (-fourth-item '(1 2 3))
@result{} nil @result{} ()
@end group
@group
(-fourth-item '(1 2 3 4 5))
@result{} 4
@end group @end group
@end example @end example
@end defun @end defun
@ -3194,16 +3206,20 @@ See also: @code{-fifth-item} (@pxref{-fifth-item}).
@defun -fifth-item (list) @defun -fifth-item (list)
Return the fifth item of @var{list}, or @code{nil} if @var{list} is too short. Return the fifth item of @var{list}, or @code{nil} if @var{list} is too short.
See also: @code{-last-item} (@pxref{-last-item}). See also: @code{-fourth-item} (@pxref{-fourth-item}), @code{-last-item} (@pxref{-last-item}), etc.
@example @example
@group @group
(-fifth-item '(1 2 3 4 5)) (-fifth-item ())
@result{} 5 @result{} ()
@end group @end group
@group @group
(-fifth-item nil) (-fifth-item '(1 2 3 4))
@result{} nil @result{} ()
@end group
@group
(-fifth-item '(1 2 3 4 5))
@result{} 5
@end group @end group
@end example @end example
@end defun @end defun
@ -3212,14 +3228,16 @@ See also: @code{-last-item} (@pxref{-last-item}).
@defun -last-item (list) @defun -last-item (list)
Return the last item of @var{list}, or @code{nil} on an empty list. Return the last item of @var{list}, or @code{nil} on an empty list.
See also: @code{-first-item} (@pxref{-first-item}), etc.
@example @example
@group @group
(-last-item '(1 2 3)) (-last-item ())
@result{} 3 @result{} ()
@end group @end group
@group @group
(-last-item nil) (-last-item '(1 2 3 4 5))
@result{} nil @result{} 5
@end group @end group
@group @group
(let ((list (list 1 2 3))) (setf (-last-item list) 5) list) (let ((list (list 1 2 3))) (setf (-last-item list) 5) list)

38
dev/examples.el
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@ -1229,30 +1229,42 @@ related predicates."
(--last (> (length it) 3) '("a" "looong" "word" "and" "short" "one")) => "short") (--last (> (length it) 3) '("a" "looong" "word" "and" "short" "one")) => "short")
(defexamples -first-item (defexamples -first-item
(-first-item '(1 2 3)) => 1 (-first-item '()) => '()
(-first-item nil) => nil (-first-item '(1 2 3 4 5)) => 1
(let ((list (list 1 2 3))) (setf (-first-item list) 5) list) => '(5 2 3)) (let ((list (list 1 2 3))) (setf (-first-item list) 5) list) => '(5 2 3)
(-first-item 1) !!> wrong-type-argument)
(defexamples -second-item (defexamples -second-item
(-second-item '(1 2 3)) => 2 (-second-item '()) => '()
(-second-item nil) => nil) (-second-item '(1 2 3 4 5)) => 2
(let ((list (list 1 2))) (setf (-second-item list) 5) list) => '(1 5)
(-second-item '(1)) => '()
(-second-item 1) !!> wrong-type-argument)
(defexamples -third-item (defexamples -third-item
(-third-item '(1 2 3)) => 3 (-third-item '()) => '()
(-third-item nil) => nil) (-third-item '(1 2)) => '()
(-third-item '(1 2 3 4 5)) => 3
(-third-item 1) !!> wrong-type-argument)
(defexamples -fourth-item (defexamples -fourth-item
(-fourth-item '(1 2 3 4)) => 4 (-fourth-item '()) => '()
(-fourth-item nil) => nil) (-fourth-item '(1 2 3)) => '()
(-fourth-item '(1 2 3 4 5)) => 4
(-fourth-item 1) !!> wrong-type-argument)
(defexamples -fifth-item (defexamples -fifth-item
(-fifth-item '()) => '()
(-fifth-item '(1 2 3 4)) => '()
(-fifth-item '(1 2 3 4 5)) => 5 (-fifth-item '(1 2 3 4 5)) => 5
(-fifth-item nil) => nil) (-fifth-item 1) !!> wrong-type-argument)
(defexamples -last-item (defexamples -last-item
(-last-item '(1 2 3)) => 3 (-last-item '()) => '()
(-last-item nil) => nil (-last-item '(1 2 3 4 5)) => 5
(let ((list (list 1 2 3))) (setf (-last-item list) 5) list) => '(1 2 5)) (let ((list (list 1 2 3))) (setf (-last-item list) 5) list) => '(1 2 5)
(-last-item '(1)) => 1
(-last-item 1) !!> wrong-type-argument)
(defexamples -butlast (defexamples -butlast
(-butlast '(1 2 3)) => '(1 2) (-butlast '(1 2 3)) => '(1 2)

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