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1

How do I check if myList is empty? Following (is my attempt) prints "NOT empty" when, in fact, the list is empty.

documentclassstandalone
usepackageexpl3
begindocument
 ExplSyntaxOn
 clist_new:NmyList
 clist_set:NnmyList
 cs_if_eq:NNTFmyListEMPTYNOT empty
 ExplSyntaxOff
enddocument

EDIT: I found a way to do so (below) but would like you to share another approach (it's interesting to see how else it can be done):

 clist_new:NmyList
 clist_new:NemptyList
 clist_set:NnmyList % assign "emptiness" to the list (although it had already been empty to begin with)
 cs_if_eq:NNTFmyListemptyListEMPTYNOT empty

conditionals expl3 latex3 comma-separated-list

share|improve this question

edited 5 hours ago

bp2017

asked 5 hours ago

bp2017bp2017

920116

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  clist_if_empty:NTF.
  
  – Ulrike Fischer
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  What Ulrike said, plus the “proper” way to make a clist empty is clist_clear:N myList. (Deep down is basically the same, but exist for semantics).
  
  – Phelype Oleinik
  4 hours ago
  

  
  
  
  

add a comment | 

1

How do I check if myList is empty? Following (is my attempt) prints "NOT empty" when, in fact, the list is empty.

documentclassstandalone
usepackageexpl3
begindocument
 ExplSyntaxOn
 clist_new:NmyList
 clist_set:NnmyList
 cs_if_eq:NNTFmyListEMPTYNOT empty
 ExplSyntaxOff
enddocument

EDIT: I found a way to do so (below) but would like you to share another approach (it's interesting to see how else it can be done):

 clist_new:NmyList
 clist_new:NemptyList
 clist_set:NnmyList % assign "emptiness" to the list (although it had already been empty to begin with)
 cs_if_eq:NNTFmyListemptyListEMPTYNOT empty

conditionals expl3 latex3 comma-separated-list

share|improve this question

edited 5 hours ago

bp2017

asked 5 hours ago

bp2017bp2017

920116

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  clist_if_empty:NTF.
  
  – Ulrike Fischer
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  What Ulrike said, plus the “proper” way to make a clist empty is clist_clear:N myList. (Deep down is basically the same, but exist for semantics).
  
  – Phelype Oleinik
  4 hours ago
  

  
  
  
  

add a comment | 

How do I check if myList is empty? Following (is my attempt) prints "NOT empty" when, in fact, the list is empty.

documentclassstandalone
usepackageexpl3
begindocument
 ExplSyntaxOn
 clist_new:NmyList
 clist_set:NnmyList
 cs_if_eq:NNTFmyListEMPTYNOT empty
 ExplSyntaxOff
enddocument

EDIT: I found a way to do so (below) but would like you to share another approach (it's interesting to see how else it can be done):

 clist_new:NmyList
 clist_new:NemptyList
 clist_set:NnmyList % assign "emptiness" to the list (although it had already been empty to begin with)
 cs_if_eq:NNTFmyListemptyListEMPTYNOT empty

conditionals expl3 latex3 comma-separated-list

share|improve this question

edited 5 hours ago

bp2017

asked 5 hours ago

bp2017bp2017

920116

documentclassstandalone
usepackageexpl3
begindocument
 ExplSyntaxOn
 clist_new:NmyList
 clist_set:NnmyList
 cs_if_eq:NNTFmyListEMPTYNOT empty
 ExplSyntaxOff
enddocument

 clist_new:NmyList
 clist_new:NemptyList
 clist_set:NnmyList % assign "emptiness" to the list (although it had already been empty to begin with)
 cs_if_eq:NNTFmyListemptyListEMPTYNOT empty

share|improve this question

edited 5 hours ago

bp2017

asked 5 hours ago

bp2017bp2017

920116

share|improve this question

edited 5 hours ago

bp2017

asked 5 hours ago

bp2017bp2017

920116

asked 5 hours ago

bp2017bp2017

920116

asked 5 hours ago

bp2017bp2017

920116

2 Answers
2

active

oldest

votes

4

documentclassstandalone
usepackageexpl3
begindocument
ExplSyntaxOn
clist_new:NmyList
clist_set:NnmyList
clist_if_empty:NTF myList EMPTY NOT EMPTY 
ExplSyntaxOff
enddocument

run texdoc l3clist

share|improve this answer

answered 4 hours ago

Red-CloudRed-Cloud

2,04312

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  How can I use AND (&&) during this clist_if_empty check to also perform check on additional list (or on something else) in one directive?
  
  – bp2017
  4 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  See bool_if:nTF or (better) e.g. bool_lazy_or:nnTF, all in interface3.
  
  – Joseph Wright♦
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @JosephWright, thank you. I've seen those and read a bit about them but I have no idea how to combine them with a conditional statement like clist_if_empty. I'll take a look again and see if I can find this information this time.
  
  – bp2017
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bp2017 You can always use the c-type variants, e..g clist_new:c myList2 . Note though that there is no escaping the catcode and token basis of TeX. Also note that standard expl3 style would be l_bp_mylist_clist or similar.
  
  – Joseph Wright♦
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bp2017 You want the predicates: clist_if_empty_p:N, and so on
  
  – Joseph Wright♦
  3 hours ago
  

  
  
  
  

 | 
show 2 more comments

6

The test you want is clist_if_empty:N(TF): each data type has an appropriate test for emptiness or similar. These are defined such that they are 'aware' of the internal nature of data types (for example an empty prop is not entirely empty at the macro level).

Your cs_if_empty:NN(TF) test is wrong as the second argument you have given is no N type (a single token), but is rather n-type (in this case, an empty token list). You could in this case do a low-level test, for example

cs_if_eq:NN(TF) myList c_empty_clist <true> <false> 

or by expanding the list to a 'raw' token list

tl_if_blank:V(TF) c_empty_clist <true> <false> 

share|improve this answer

answered 4 hours ago

Joseph Wright♦Joseph Wright

207k23568897

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  There is a style in tikzset named myStyle, I tried to pass #1 of that style (which contains all the arguments passed to the style, supplied through a node or a path directive which calls that style with or without arguments) inside /utils/exec as clist_set:NnmyList#1. But for some reason when the style is used with no arguments (like path node[myStyle];), the list is NOT empty (it's empty only when path node[myStyle=];). I'm trying to figure out why I get such result (and trying to look what #1 contains in this case, but having difficulties so far).
  
  – bp2017
  4 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bp2017 There is some 'back end' in pgf that may be responsible, but I'd be tempted just to showtokens the input #1.
  
  – Joseph Wright♦
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Great! Here is the answer: showtokens pgfkeysnovalue . So I'll be checking against this pgfkeysnovalue in case no arguments were supplied at all.
  
  – bp2017
  4 hours ago
  
  

  
  
  
  

add a comment | 

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4

documentclassstandalone
usepackageexpl3
begindocument
ExplSyntaxOn
clist_new:NmyList
clist_set:NnmyList
clist_if_empty:NTF myList EMPTY NOT EMPTY 
ExplSyntaxOff
enddocument

run texdoc l3clist

share|improve this answer

answered 4 hours ago

Red-CloudRed-Cloud

2,04312

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  How can I use AND (&&) during this clist_if_empty check to also perform check on additional list (or on something else) in one directive?
  
  – bp2017
  4 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  See bool_if:nTF or (better) e.g. bool_lazy_or:nnTF, all in interface3.
  
  – Joseph Wright♦
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @JosephWright, thank you. I've seen those and read a bit about them but I have no idea how to combine them with a conditional statement like clist_if_empty. I'll take a look again and see if I can find this information this time.
  
  – bp2017
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bp2017 You can always use the c-type variants, e..g clist_new:c myList2 . Note though that there is no escaping the catcode and token basis of TeX. Also note that standard expl3 style would be l_bp_mylist_clist or similar.
  
  – Joseph Wright♦
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bp2017 You want the predicates: clist_if_empty_p:N, and so on
  
  – Joseph Wright♦
  3 hours ago
  

  
  
  
  

 | 
show 2 more comments

4

documentclassstandalone
usepackageexpl3
begindocument
ExplSyntaxOn
clist_new:NmyList
clist_set:NnmyList
clist_if_empty:NTF myList EMPTY NOT EMPTY 
ExplSyntaxOff
enddocument

run texdoc l3clist

share|improve this answer

answered 4 hours ago

Red-CloudRed-Cloud

2,04312

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  How can I use AND (&&) during this clist_if_empty check to also perform check on additional list (or on something else) in one directive?
  
  – bp2017
  4 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  See bool_if:nTF or (better) e.g. bool_lazy_or:nnTF, all in interface3.
  
  – Joseph Wright♦
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @JosephWright, thank you. I've seen those and read a bit about them but I have no idea how to combine them with a conditional statement like clist_if_empty. I'll take a look again and see if I can find this information this time.
  
  – bp2017
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bp2017 You can always use the c-type variants, e..g clist_new:c myList2 . Note though that there is no escaping the catcode and token basis of TeX. Also note that standard expl3 style would be l_bp_mylist_clist or similar.
  
  – Joseph Wright♦
  3 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bp2017 You want the predicates: clist_if_empty_p:N, and so on
  
  – Joseph Wright♦
  3 hours ago
  

  
  
  
  

 | 
show 2 more comments

documentclassstandalone
usepackageexpl3
begindocument
ExplSyntaxOn
clist_new:NmyList
clist_set:NnmyList
clist_if_empty:NTF myList EMPTY NOT EMPTY 
ExplSyntaxOff
enddocument

run texdoc l3clist

share|improve this answer

answered 4 hours ago

Red-CloudRed-Cloud

2,04312

documentclassstandalone
usepackageexpl3
begindocument
ExplSyntaxOn
clist_new:NmyList
clist_set:NnmyList
clist_if_empty:NTF myList EMPTY NOT EMPTY 
ExplSyntaxOff
enddocument

share|improve this answer

answered 4 hours ago

Red-CloudRed-Cloud

2,04312

answered 4 hours ago

Red-CloudRed-Cloud

2,04312

answered 4 hours ago

Red-CloudRed-Cloud

2,04312

6

The test you want is clist_if_empty:N(TF): each data type has an appropriate test for emptiness or similar. These are defined such that they are 'aware' of the internal nature of data types (for example an empty prop is not entirely empty at the macro level).

Your cs_if_empty:NN(TF) test is wrong as the second argument you have given is no N type (a single token), but is rather n-type (in this case, an empty token list). You could in this case do a low-level test, for example

cs_if_eq:NN(TF) myList c_empty_clist <true> <false> 

or by expanding the list to a 'raw' token list

tl_if_blank:V(TF) c_empty_clist <true> <false> 

share|improve this answer

answered 4 hours ago

Joseph Wright♦Joseph Wright

207k23568897

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  There is a style in tikzset named myStyle, I tried to pass #1 of that style (which contains all the arguments passed to the style, supplied through a node or a path directive which calls that style with or without arguments) inside /utils/exec as clist_set:NnmyList#1. But for some reason when the style is used with no arguments (like path node[myStyle];), the list is NOT empty (it's empty only when path node[myStyle=];). I'm trying to figure out why I get such result (and trying to look what #1 contains in this case, but having difficulties so far).
  
  – bp2017
  4 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bp2017 There is some 'back end' in pgf that may be responsible, but I'd be tempted just to showtokens the input #1.
  
  – Joseph Wright♦
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Great! Here is the answer: showtokens pgfkeysnovalue . So I'll be checking against this pgfkeysnovalue in case no arguments were supplied at all.
  
  – bp2017
  4 hours ago
  
  

  
  
  
  

add a comment | 

6

The test you want is clist_if_empty:N(TF): each data type has an appropriate test for emptiness or similar. These are defined such that they are 'aware' of the internal nature of data types (for example an empty prop is not entirely empty at the macro level).

Your cs_if_empty:NN(TF) test is wrong as the second argument you have given is no N type (a single token), but is rather n-type (in this case, an empty token list). You could in this case do a low-level test, for example

cs_if_eq:NN(TF) myList c_empty_clist <true> <false> 

or by expanding the list to a 'raw' token list

tl_if_blank:V(TF) c_empty_clist <true> <false> 

share|improve this answer

answered 4 hours ago

Joseph Wright♦Joseph Wright

207k23568897

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  There is a style in tikzset named myStyle, I tried to pass #1 of that style (which contains all the arguments passed to the style, supplied through a node or a path directive which calls that style with or without arguments) inside /utils/exec as clist_set:NnmyList#1. But for some reason when the style is used with no arguments (like path node[myStyle];), the list is NOT empty (it's empty only when path node[myStyle=];). I'm trying to figure out why I get such result (and trying to look what #1 contains in this case, but having difficulties so far).
  
  – bp2017
  4 hours ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bp2017 There is some 'back end' in pgf that may be responsible, but I'd be tempted just to showtokens the input #1.
  
  – Joseph Wright♦
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Great! Here is the answer: showtokens pgfkeysnovalue . So I'll be checking against this pgfkeysnovalue in case no arguments were supplied at all.
  
  – bp2017
  4 hours ago
  
  

  
  
  
  

add a comment | 

The test you want is clist_if_empty:N(TF): each data type has an appropriate test for emptiness or similar. These are defined such that they are 'aware' of the internal nature of data types (for example an empty prop is not entirely empty at the macro level).

Your cs_if_empty:NN(TF) test is wrong as the second argument you have given is no N type (a single token), but is rather n-type (in this case, an empty token list). You could in this case do a low-level test, for example

cs_if_eq:NN(TF) myList c_empty_clist <true> <false> 

or by expanding the list to a 'raw' token list

tl_if_blank:V(TF) c_empty_clist <true> <false> 

share|improve this answer

answered 4 hours ago

Joseph Wright♦Joseph Wright

207k23568897

cs_if_eq:NN(TF) myList c_empty_clist <true> <false> 

tl_if_blank:V(TF) c_empty_clist <true> <false> 

share|improve this answer

answered 4 hours ago

Joseph Wright♦Joseph Wright

207k23568897

answered 4 hours ago

Joseph Wright♦Joseph Wright

207k23568897

answered 4 hours ago

Joseph Wright♦Joseph Wright

207k23568897