branch: externals/dash
commit 88737493cd7fdded213b8fa2a3c2bf832dae9517
Author: Basil L. Contovounesios <conto...@tcd.ie>
Commit: Basil L. Contovounesios <conto...@tcd.ie>
Improve and simplify right-associative reductions
* Translate recursion to iteration to avoid exceeding
max-lisp-eval-depth.
* Rewrite functions in terms of anaphoric macros.
* Expand test cases.
---
dash.el | 43 ++++++++++++++++++++-----------------------
dev/examples.el | 40 +++++++++++++++++++++++-----------------
2 files changed, 43 insertions(+), 40 deletions(-)
diff --git a/dash.el b/dash.el
index 8d1d9a6..e0437b8 100644
--- a/dash.el
+++ b/dash.el
@@ -205,7 +205,7 @@ Return nil, used for side-effects only."
"Return the result of applying FN to INITIAL-VALUE and the
first item in LIST, then applying FN to that result and the 2nd
item, etc. If LIST contains no items, return INITIAL-VALUE and
-FN is not called.
+do not call FN.
In the anaphoric form `--reduce-from', the accumulated value is
exposed as symbol `acc'.
@@ -225,9 +225,9 @@ See also: `-reduce', `-reduce-r'"
(defun -reduce (fn list)
"Return the result of applying FN to the first 2 items in LIST,
then applying FN to that result and the 3rd item, etc. If LIST
-contains no items, FN must accept no arguments as well, and
-reduce return the result of calling FN with no arguments. If
-LIST has only 1 item, it is returned and FN is not called.
+contains no items, return the result of calling FN with no
+arguments. If LIST contains a single item, return that item
+and do not call FN.
In the anaphoric form `--reduce', the accumulated value is
exposed as symbol `acc'.
@@ -237,6 +237,11 @@ See also: `-reduce-from', `-reduce-r'"
(-reduce-from fn (car list) (cdr list))
(funcall fn)))
+(defmacro --reduce-r-from (form initial-value list)
+ "Anaphoric version of `-reduce-r-from'."
+ (declare (debug (form form form)))
+ `(--reduce-from ,form ,initial-value (reverse ,list)))
+
(defun -reduce-r-from (fn initial-value list)
"Replace conses with FN, nil with INITIAL-VALUE and evaluate
the resulting expression. If LIST is empty, INITIAL-VALUE is
@@ -246,20 +251,18 @@ Note: this function works the same as `-reduce-from' but
the
operation associates from right instead of from left.
See also: `-reduce-r', `-reduce'"
- (if (not list) initial-value
- (funcall fn (car list) (-reduce-r-from fn initial-value (cdr list)))))
+ (--reduce-r-from (funcall fn it acc) initial-value list))
-(defmacro --reduce-r-from (form initial-value list)
- "Anaphoric version of `-reduce-r-from'."
- (declare (debug (form form form)))
- `(-reduce-r-from (lambda (&optional it acc) ,form) ,initial-value ,list))
+(defmacro --reduce-r (form list)
+ "Anaphoric version of `-reduce-r'."
+ (declare (debug (form form)))
+ `(--reduce ,form (reverse ,list)))
(defun -reduce-r (fn list)
"Replace conses with FN and evaluate the resulting expression.
-The final nil is ignored. If LIST contains no items, FN must
-accept no arguments as well, and reduce return the result of
-calling FN with no arguments. If LIST has only 1 item, it is
-returned and FN is not called.
+The final nil is ignored. If LIST contains no items, return the
+result of calling FN with no arguments. If LIST contains a single
+item, return that item and do not call FN.
The first argument of FN is the new item, the second is the
accumulated value.
@@ -268,15 +271,9 @@ Note: this function works the same as `-reduce' but the
operation
associates from right instead of from left.
See also: `-reduce-r-from', `-reduce'"
- (cond
- ((not list) (funcall fn))
- ((not (cdr list)) (car list))
- (t (funcall fn (car list) (-reduce-r fn (cdr list))))))
-
-(defmacro --reduce-r (form list)
- "Anaphoric version of `-reduce-r'."
- (declare (debug (form form)))
- `(-reduce-r (lambda (&optional it acc) ,form) ,list))
+ (if list
+ (--reduce-r (funcall fn it acc) list)
+ (funcall fn)))
(defun -reductions-from (fn init list)
"Return a list of the intermediate values of the reduction.
diff --git a/dev/examples.el b/dev/examples.el
index 05669e9..7ae2d1f 100644
--- a/dev/examples.el
+++ b/dev/examples.el
@@ -303,34 +303,40 @@ new list."
(defexamples -reduce-from
(-reduce-from '- 10 '(1 2 3)) => 4
- (-reduce-from (lambda (memo item)
- (concat "(" memo " - " (int-to-string item) ")")) "10" '(1
2 3)) => "(((10 - 1) - 2) - 3)"
- (--reduce-from (concat acc " " it) "START" '("a" "b" "c"))
=> "START a b c"
- (-reduce-from '+ 7 '()) => 7
- (-reduce-from '+ 7 '(1)) => 8)
+ (-reduce-from (lambda (memo item) (format "(%s - %d)" memo item)) "10" '(1
2 3)) => "(((10 - 1) - 2) - 3)"
+ (--reduce-from (concat acc " " it) "START" '("a" "b" "c")) => "START a b c"
+ (--reduce-from (- acc it) 10 '(1 2 3)) => 4
+ (--reduce-from (- acc it) 10 '(1)) => 9
+ (--reduce-from (- acc it) 10 '()) => 10
+ (-reduce-from '- 7 '(1)) => 6
+ (-reduce-from '- 7 '()) => 7)
(defexamples -reduce-r-from
(-reduce-r-from '- 10 '(1 2 3)) => -8
- (-reduce-r-from (lambda (item memo)
- (concat "(" (int-to-string item) " - " memo ")")) "10"
'(1 2 3)) => "(1 - (2 - (3 - 10)))"
- (--reduce-r-from (concat it " " acc) "END" '("a" "b"
"c")) => "a b c END"
- (-reduce-r-from '+ 7 '()) => 7
- (-reduce-r-from '+ 7 '(1)) => 8)
+ (-reduce-r-from (lambda (item memo) (format "(%d - %s)" item memo)) "10"
'(1 2 3)) => "(1 - (2 - (3 - 10)))"
+ (--reduce-r-from (concat it " " acc) "END" '("a" "b" "c")) => "a b c END"
+ (--reduce-r-from (- it acc) 10 '(1 2 3)) => -8
+ (--reduce-r-from (- it acc) 10 '(1)) => -9
+ (--reduce-r-from (- it acc) 10 '()) => 10
+ (-reduce-r-from '- 7 '(1)) => -6
+ (-reduce-r-from '- 7 '()) => 7)
(defexamples -reduce
(-reduce '- '(1 2 3 4)) => -8
- (-reduce (lambda (memo item) (format "%s-%s" memo item)) '(1 2 3)) =>
"1-2-3"
- (--reduce (format "%s-%s" acc it) '(1 2 3)) => "1-2-3"
- (-reduce '+ '()) => 0
- (-reduce '+ '(1)) => 1
+ (-reduce 'list '(1 2 3 4)) => '(((1 2) 3) 4)
+ (--reduce (format "%s-%d" acc it) '(1 2 3)) => "1-2-3"
+ (-reduce '- '()) => 0
+ (-reduce '- '(1)) => 1
+ (--reduce (- acc it) '(1)) => 1
(--reduce (format "%s-%s" acc it) '()) => "nil-nil")
(defexamples -reduce-r
(-reduce-r '- '(1 2 3 4)) => -2
- (-reduce-r (lambda (item memo) (format "%s-%s" memo item)) '(1 2 3)) =>
"3-2-1"
- (--reduce-r (format "%s-%s" acc it) '(1 2 3)) => "3-2-1"
+ (-reduce-r (lambda (item memo) (format "%s-%d" memo item)) '(1 2 3)) =>
"3-2-1"
+ (--reduce-r (format "%s-%d" acc it) '(1 2 3)) => "3-2-1"
(-reduce-r '+ '()) => 0
- (-reduce-r '+ '(1)) => 1
+ (-reduce-r '- '(1)) => 1
+ (--reduce (- it acc) '(1)) => 1
(--reduce-r (format "%s-%s" it acc) '()) => "nil-nil")
(defexamples -reductions-from
