Questions tagged [equality]
The equality tag has no usage guidance.
15
questions
3
votes
1
answer
40
views
Strange behaviour involving `display` property
I noticed a rather peculiar behavior when using the display property (using emacs 28.2). I tried to boil things down to a minimal example: The code
(defun finsert ()
(insert (propertize ".&...
- 175
0
votes
1
answer
21
views
If-clause on content of variable
Question:
I customized the variable user-mail-address on PC 1 and thought, I simply could ask for the content of this variable:
(setq org-agenda-files
(if (user-mail-address "[email protected]&...
- 508
7
votes
1
answer
132
views
“(equal a b)⇒t” whereas “(equal b a)⇒error”
GNU Emacs Lisp Reference Manual, 2.8 Equality Predicates:
Comparing circular lists may therefore cause deep recursion that leads to an error, and this may result in counterintuitive behavior such as (...
- 4,583
0
votes
1
answer
23
views
Adding to a list when there is a match only
The following function replaces filenames and places the result in a list. Although the list gets filled, I do not want to add the filename when there is no match. How can I avoid sending non-...
- 1
1
vote
1
answer
70
views
How to use markers as keys in a hash map?
I'm creating a hash map and I'd like to use markers as keys. I set the hash map equality test to "equal", but the last line from the below code is returning ("bye" "fly") ...
- 113
2
votes
2
answers
766
views
setf + alist-get but with "equal" instead of "eq"?
I got a suggestion to use setf to replace value in an alist: Replace element in a list / add in case of absence, with custom test/key functions
The example was provided, but it doesn't work if key is ...
- 3,362
1
vote
2
answers
254
views
How to compare an item against others, that's compatible with string-equal?
When comparing the last-command against multiple possible strings, it doesn't seem possible to use the member function.
Is there a way to simplify this using something like member?
(when
(or
(...
- 8,546
5
votes
1
answer
271
views
Set difference for sets of strings
Why the following in emacs-lisp works as expected:
(set-difference '(1 2) '(1))
=> (2)
But if strings used it doesn't:
(set-difference '("foo" "bar") '("foo"))
=> ("foo" "bar")
How do can I ...
- 1,233
0
votes
1
answer
109
views
Function that returns the name of a Greek vowel
I'm trying to write a function that will return the name of a
Greek vowel: alpha or epsilon etc. I was hoping this could be done
by extracting it from the second group in the following regexp
(in a ...
- 3,254
6
votes
2
answers
475
views
How to make (make-symbol "foo") (make-symbol "foo") equal?
I'm curious why:
(equal (make-symbol "foo") (make-symbol "foo"))
ends up beeing nil.
While
(equal 'foo 'foo)
is t.
Do i have a misconception of symbols?
Aren't they just strings without double-...
- 131
4
votes
3
answers
1k
views
Why are there multiple ways to test for equality in elisp?
In Logic there is one and only one unambiguously(*) defined notion of equality: two things are equal if and only if they are the same thing.
Programming languages of course try to emulate this ...
- 839
0
votes
1
answer
57
views
Idiomatic boolean comparators
Are there idiomatic boolean comparators in emacs lisp?
Something like:
(my/bool< nil t)
=> t
(my/bool< 1 2)
=> nil
For example, a comparator that returns t if the first argument is ...
- 7,389
2
votes
1
answer
390
views
Check if buffername is equal to file name
I'm trying to autoexport a file from orgmode to html, so I decided to make a function to check the major mode of the buffer and check if the buffer has open the file that I want to export but when I ...
- 381
1
vote
1
answer
62
views
Comparison of quoted symbols fails using equal
I'm trying to compare (quote foo) with 'foo using equal, but the equality is failing. Here is a trace of what is happening with my code. I don't understand why the comparison fails -- does it have ...
- 1,308
6
votes
1
answer
88
views
More than two variable for equality predicates?
I see that = is great for "comparing" more than two (numerical) arguments, e.g., (= 1 1 1). But then eq, eql, and equal all only allow two arguments. And nesting is nonsense, i.e., the inner eq ...
- 2,937