How to write a list literal with conditional items? [duplicate]

This question already has an answer here:

How to evaluate the variables before adding them to a list?

2 answers

Given a list literal '(1 2 3)

is it possible to conditionally include parts of the list?

eg:

'(1 2 3

  (when thing-is-true '(10 11 12)))

  4 5 6)

Which would result in

'(1 2 3 4 5 6) or '(1 2 3 10 11 12 4 5 6) dependent on thing-is-true.

Python for example supports:

[1, 2, 3, *([10, 11, 12] if thing_is_true else ), 4, 5, 6]

What is the most straightforward way to achieve this using a single expression, without defining a list variable and manipulating it?

edited 16 hours ago

asked 19 hours ago

ideasman42

1,555625

marked as duplicate by npostavs, DoMiNeLa10♦ 11 hours ago

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Don't think this is a duplicate because I'm not asking about adding items to a list. Rather, how to declare a list. Also notice the answer to this question is quite different.

– ideasman42
16 hours ago

Hmm, I guess there is minor difference in that the dup's answer doesn't mention ,@, only ,; but to my mind the answer in both cases is essentially: "you're looking for backquote".

– npostavs
10 hours ago

I was aware of the feature (that it could be useful in this case), I just didn't know how to use it because I'm not that experienced in elisp.

– ideasman42
9 hours ago

1

I'm not aware of what you're aware of, I just talk about what's written in the question and vote accordingly.

– npostavs
9 hours ago

Seems like a dup to me, regardless of a minor difference in what you're trying to do. The question is really about a misunderstanding, and the referenced duplicate Q&A covers that. (And the tags should include quote and not include elisp, IMO.)

– Drew
6 hours ago

|
show 1 more comment

This question already has an answer here:

How to evaluate the variables before adding them to a list?

2 answers

Given a list literal '(1 2 3)

is it possible to conditionally include parts of the list?

eg:

'(1 2 3

  (when thing-is-true '(10 11 12)))

  4 5 6)

Which would result in

'(1 2 3 4 5 6) or '(1 2 3 10 11 12 4 5 6) dependent on thing-is-true.

Python for example supports:

[1, 2, 3, *([10, 11, 12] if thing_is_true else ), 4, 5, 6]

What is the most straightforward way to achieve this using a single expression, without defining a list variable and manipulating it?

edited 16 hours ago

asked 19 hours ago

ideasman42

1,555625

marked as duplicate by npostavs, DoMiNeLa10♦ 11 hours ago

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Don't think this is a duplicate because I'm not asking about adding items to a list. Rather, how to declare a list. Also notice the answer to this question is quite different.

– ideasman42
16 hours ago

Hmm, I guess there is minor difference in that the dup's answer doesn't mention ,@, only ,; but to my mind the answer in both cases is essentially: "you're looking for backquote".

– npostavs
10 hours ago

I was aware of the feature (that it could be useful in this case), I just didn't know how to use it because I'm not that experienced in elisp.

– ideasman42
9 hours ago

1

I'm not aware of what you're aware of, I just talk about what's written in the question and vote accordingly.

– npostavs
9 hours ago

Seems like a dup to me, regardless of a minor difference in what you're trying to do. The question is really about a misunderstanding, and the referenced duplicate Q&A covers that. (And the tags should include quote and not include elisp, IMO.)

– Drew
6 hours ago

|
show 1 more comment

This question already has an answer here:

How to evaluate the variables before adding them to a list?

2 answers

Given a list literal '(1 2 3)

is it possible to conditionally include parts of the list?

eg:

'(1 2 3

  (when thing-is-true '(10 11 12)))

  4 5 6)

Which would result in

'(1 2 3 4 5 6) or '(1 2 3 10 11 12 4 5 6) dependent on thing-is-true.

Python for example supports:

[1, 2, 3, *([10, 11, 12] if thing_is_true else ), 4, 5, 6]

What is the most straightforward way to achieve this using a single expression, without defining a list variable and manipulating it?

edited 16 hours ago

asked 19 hours ago

ideasman42

1,555625

This question already has an answer here:

How to evaluate the variables before adding them to a list?

2 answers

Given a list literal '(1 2 3)

is it possible to conditionally include parts of the list?

eg:

'(1 2 3

  (when thing-is-true '(10 11 12)))

  4 5 6)

Which would result in

'(1 2 3 4 5 6) or '(1 2 3 10 11 12 4 5 6) dependent on thing-is-true.

Python for example supports:

[1, 2, 3, *([10, 11, 12] if thing_is_true else ), 4, 5, 6]

What is the most straightforward way to achieve this using a single expression, without defining a list variable and manipulating it?

This question already has an answer here:

How to evaluate the variables before adding them to a list?

2 answers

elisp list

edited 16 hours ago

asked 19 hours ago

ideasman42

1,555625

edited 16 hours ago

asked 19 hours ago

ideasman42

1,555625

edited 16 hours ago

asked 19 hours ago

ideasman42

1,555625

asked 19 hours ago

ideasman42

1,555625

asked 19 hours ago

ideasman42

1,555625

marked as duplicate by npostavs, DoMiNeLa10♦ 11 hours ago

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

marked as duplicate by npostavs, DoMiNeLa10♦ 11 hours ago

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Don't think this is a duplicate because I'm not asking about adding items to a list. Rather, how to declare a list. Also notice the answer to this question is quite different.

– ideasman42
16 hours ago

Hmm, I guess there is minor difference in that the dup's answer doesn't mention ,@, only ,; but to my mind the answer in both cases is essentially: "you're looking for backquote".

– npostavs
10 hours ago

I was aware of the feature (that it could be useful in this case), I just didn't know how to use it because I'm not that experienced in elisp.

– ideasman42
9 hours ago

1

I'm not aware of what you're aware of, I just talk about what's written in the question and vote accordingly.

– npostavs
9 hours ago

Seems like a dup to me, regardless of a minor difference in what you're trying to do. The question is really about a misunderstanding, and the referenced duplicate Q&A covers that. (And the tags should include quote and not include elisp, IMO.)

– Drew
6 hours ago

|
show 1 more comment

Don't think this is a duplicate because I'm not asking about adding items to a list. Rather, how to declare a list. Also notice the answer to this question is quite different.

– ideasman42
16 hours ago

Hmm, I guess there is minor difference in that the dup's answer doesn't mention ,@, only ,; but to my mind the answer in both cases is essentially: "you're looking for backquote".

– npostavs
10 hours ago

I was aware of the feature (that it could be useful in this case), I just didn't know how to use it because I'm not that experienced in elisp.

– ideasman42
9 hours ago

1

I'm not aware of what you're aware of, I just talk about what's written in the question and vote accordingly.

– npostavs
9 hours ago

Seems like a dup to me, regardless of a minor difference in what you're trying to do. The question is really about a misunderstanding, and the referenced duplicate Q&A covers that. (And the tags should include quote and not include elisp, IMO.)

– Drew
6 hours ago

Don't think this is a duplicate because I'm not asking about adding items to a list. Rather, how to declare a list. Also notice the answer to this question is quite different.

– ideasman42
16 hours ago

Hmm, I guess there is minor difference in that the dup's answer doesn't mention ,@, only ,; but to my mind the answer in both cases is essentially: "you're looking for backquote".

– npostavs
10 hours ago

I was aware of the feature (that it could be useful in this case), I just didn't know how to use it because I'm not that experienced in elisp.

– ideasman42
9 hours ago

I'm not aware of what you're aware of, I just talk about what's written in the question and vote accordingly.

– npostavs
9 hours ago

Seems like a dup to me, regardless of a minor difference in what you're trying to do. The question is really about a misunderstanding, and the referenced duplicate Q&A covers that. (And the tags should include quote and not include elisp, IMO.)

– Drew
6 hours ago

|
show 1 more comment

1 Answer
1

active

oldest

votes

You can use the macro (elisp) Backquote, e.g.,

`(1 2 3 ,@(when nil '(10 11 12)) 4 5 6)

;; => (1 2 3 4 5 6)



`(1 2 3 ,@(when t '(10 11 12)) 4 5 6)

;; => (1 2 3 10 11 12 4 5 6)

if you expand the above macros, they are simply using append

(append '(1 2 3) (when nil '(10 11 12)) '(4 5 6))

;; => (1 2 3 4 5 6)



(append '(1 2 3) (when t '(10 11 12)) '(4 5 6))

;; => (1 2 3 10 11 12 4 5 6)

answered 17 hours ago

xuchunyang

8,8791926

add a comment |

1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

You can use the macro (elisp) Backquote, e.g.,

`(1 2 3 ,@(when nil '(10 11 12)) 4 5 6)

;; => (1 2 3 4 5 6)



`(1 2 3 ,@(when t '(10 11 12)) 4 5 6)

;; => (1 2 3 10 11 12 4 5 6)

if you expand the above macros, they are simply using append

(append '(1 2 3) (when nil '(10 11 12)) '(4 5 6))

;; => (1 2 3 4 5 6)



(append '(1 2 3) (when t '(10 11 12)) '(4 5 6))

;; => (1 2 3 10 11 12 4 5 6)

answered 17 hours ago

xuchunyang

8,8791926

add a comment |

You can use the macro (elisp) Backquote, e.g.,

`(1 2 3 ,@(when nil '(10 11 12)) 4 5 6)

;; => (1 2 3 4 5 6)



`(1 2 3 ,@(when t '(10 11 12)) 4 5 6)

;; => (1 2 3 10 11 12 4 5 6)

if you expand the above macros, they are simply using append

(append '(1 2 3) (when nil '(10 11 12)) '(4 5 6))

;; => (1 2 3 4 5 6)



(append '(1 2 3) (when t '(10 11 12)) '(4 5 6))

;; => (1 2 3 10 11 12 4 5 6)

answered 17 hours ago

xuchunyang

8,8791926

add a comment |

You can use the macro (elisp) Backquote, e.g.,

`(1 2 3 ,@(when nil '(10 11 12)) 4 5 6)

;; => (1 2 3 4 5 6)



`(1 2 3 ,@(when t '(10 11 12)) 4 5 6)

;; => (1 2 3 10 11 12 4 5 6)

if you expand the above macros, they are simply using append

(append '(1 2 3) (when nil '(10 11 12)) '(4 5 6))

;; => (1 2 3 4 5 6)



(append '(1 2 3) (when t '(10 11 12)) '(4 5 6))

;; => (1 2 3 10 11 12 4 5 6)

answered 17 hours ago

xuchunyang

8,8791926

You can use the macro (elisp) Backquote, e.g.,

`(1 2 3 ,@(when nil '(10 11 12)) 4 5 6)

;; => (1 2 3 4 5 6)



`(1 2 3 ,@(when t '(10 11 12)) 4 5 6)

;; => (1 2 3 10 11 12 4 5 6)

if you expand the above macros, they are simply using append

(append '(1 2 3) (when nil '(10 11 12)) '(4 5 6))

;; => (1 2 3 4 5 6)



(append '(1 2 3) (when t '(10 11 12)) '(4 5 6))

;; => (1 2 3 10 11 12 4 5 6)

answered 17 hours ago

xuchunyang

8,8791926

answered 17 hours ago

xuchunyang

8,8791926

answered 17 hours ago

xuchunyang

8,8791926

answered 17 hours ago

xuchunyang

8,8791926

add a comment |

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