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How to compare integers in TeX?

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.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;

8

1

I do not understand how I can compare integers in TeX.

documentclass[]article 
begindocument

if 1<>0
1 is not equal 0.
else
1 equals 0.
fi

enddocument

According to this code snippet 1 equals 0. Why? I have read that integer comparisons are done with ifnum, but this command throws errors.

tex-core conditionals

share|improve this question

edited 5 hours ago

Phelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

asked 18 hours ago

nullnull

21111 silver badge66 bronze badges

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  ifnum...else...fi is the integer comparator in TeX. However, <> is not a valid comparison. ifnum0=1relax 0 equals 1else 0 is not equal 1fi. What you wrote in your question compared the tokens 1 and <, which were not found identical, so that the else clause was invoked.
  
  – Steven B. Segletes
  18 hours ago
  
  

  
  
  
  

add a comment
 | 

8

1

I do not understand how I can compare integers in TeX.

documentclass[]article 
begindocument

if 1<>0
1 is not equal 0.
else
1 equals 0.
fi

enddocument

According to this code snippet 1 equals 0. Why? I have read that integer comparisons are done with ifnum, but this command throws errors.

tex-core conditionals

share|improve this question

edited 5 hours ago

Phelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

asked 18 hours ago

nullnull

21111 silver badge66 bronze badges

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  ifnum...else...fi is the integer comparator in TeX. However, <> is not a valid comparison. ifnum0=1relax 0 equals 1else 0 is not equal 1fi. What you wrote in your question compared the tokens 1 and <, which were not found identical, so that the else clause was invoked.
  
  – Steven B. Segletes
  18 hours ago
  
  

  
  
  
  

add a comment
 | 

I do not understand how I can compare integers in TeX.

documentclass[]article 
begindocument

if 1<>0
1 is not equal 0.
else
1 equals 0.
fi

enddocument

According to this code snippet 1 equals 0. Why? I have read that integer comparisons are done with ifnum, but this command throws errors.

tex-core conditionals

share|improve this question

edited 5 hours ago

Phelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

asked 18 hours ago

nullnull

21111 silver badge66 bronze badges

documentclass[]article 
begindocument

if 1<>0
1 is not equal 0.
else
1 equals 0.
fi

enddocument

share|improve this question

edited 5 hours ago

Phelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

asked 18 hours ago

nullnull

21111 silver badge66 bronze badges

share|improve this question

edited 5 hours ago

Phelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

asked 18 hours ago

nullnull

21111 silver badge66 bronze badges

edited 5 hours ago

Phelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

edited 5 hours ago

Phelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

asked 18 hours ago

nullnull

21111 silver badge66 bronze badges

asked 18 hours ago

nullnull

21111 silver badge66 bronze badges

2 Answers
2

active

oldest

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12

if compares two tokens, independently of what they mean. The test if 1<>0 compares 1 and < and yields false, thus you see 1 equals 0. For the sake of the example, if you had, if 11<>0 then the test would be true because TeX would compare 1 and the next 1 and would return true. Then the test:

if 11<>0
11 is not equal 0.
else
11 equals 0.
fi

would print:

<>0 11 is not equal 0.

because the tokens <>0 would not be used by if, so TeX would simply write them on the output.

To do an integer comparison you need ifnum:

ifnum 1=0
1 equals 0.
else
1 is not equal 0.
fi

Also, TeX does not have a not equal to comparison. You can only compare with <, =, or >.

share|improve this answer

edited 18 hours ago

egreg

771k9191 gold badges20132013 silver badges33693369 bronze badges

answered 18 hours ago

Phelype OleinikPhelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

add a comment
 | 

8

Just for completeness: (La)TeX does have something that is equivalent to <>: unlessifnum#1=#2.

documentclass[]article 
begindocument

unlessifnum1=0
1 is not equal 0.
else
1 equals 0.
fi

enddocument

In this case it does not make things shorter or simpler, but sometimes this helps making the code easier to understand.

share|improve this answer

edited 15 hours ago

answered 16 hours ago

Schrödinger's catSchrödinger's cat

9,5701313 silver badges2828 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This requires LaTeX. The question is tagged "tex-core".
  
  – barbara beeton
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @barbarabeeton Thanks! Corrected. The MWE is clearly LaTeX.
  
  – Schrödinger's cat
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This does not require LaTeX: it requires e-TeX extensions, which, these days, are normally enabled by default. This has probably been a “slip of the tongue” of @barbarabeeton; it is a fact, however, that, since 2015, if I recollect correctly, the LaTeX kernel requires e-TeX extensions.
  
  – GuM
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @GuM -- I accept the fact that this requires e-TeX extensions. However, I still consider "tex-core" to pertain to the original Knuthian TeX, and unless isn't there. (I know. I could have used it more than once.) This limitation is present in the "tex-core" explication: "regardless of extensions (eTeX, etc.)".
  
  – barbara beeton
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @barbarabeeton You could have used it unless it woult not yet have been implemented? ;-)
  
  – Schrödinger's cat
  9 hours ago
  
  

  
  
  
  

 | 
show 2 more comments

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12

if compares two tokens, independently of what they mean. The test if 1<>0 compares 1 and < and yields false, thus you see 1 equals 0. For the sake of the example, if you had, if 11<>0 then the test would be true because TeX would compare 1 and the next 1 and would return true. Then the test:

if 11<>0
11 is not equal 0.
else
11 equals 0.
fi

would print:

<>0 11 is not equal 0.

because the tokens <>0 would not be used by if, so TeX would simply write them on the output.

To do an integer comparison you need ifnum:

ifnum 1=0
1 equals 0.
else
1 is not equal 0.
fi

Also, TeX does not have a not equal to comparison. You can only compare with <, =, or >.

share|improve this answer

edited 18 hours ago

egreg

771k9191 gold badges20132013 silver badges33693369 bronze badges

answered 18 hours ago

Phelype OleinikPhelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

add a comment
 | 

12

if compares two tokens, independently of what they mean. The test if 1<>0 compares 1 and < and yields false, thus you see 1 equals 0. For the sake of the example, if you had, if 11<>0 then the test would be true because TeX would compare 1 and the next 1 and would return true. Then the test:

if 11<>0
11 is not equal 0.
else
11 equals 0.
fi

would print:

<>0 11 is not equal 0.

because the tokens <>0 would not be used by if, so TeX would simply write them on the output.

To do an integer comparison you need ifnum:

ifnum 1=0
1 equals 0.
else
1 is not equal 0.
fi

Also, TeX does not have a not equal to comparison. You can only compare with <, =, or >.

share|improve this answer

edited 18 hours ago

egreg

771k9191 gold badges20132013 silver badges33693369 bronze badges

answered 18 hours ago

Phelype OleinikPhelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

add a comment
 | 

if compares two tokens, independently of what they mean. The test if 1<>0 compares 1 and < and yields false, thus you see 1 equals 0. For the sake of the example, if you had, if 11<>0 then the test would be true because TeX would compare 1 and the next 1 and would return true. Then the test:

if 11<>0
11 is not equal 0.
else
11 equals 0.
fi

would print:

<>0 11 is not equal 0.

because the tokens <>0 would not be used by if, so TeX would simply write them on the output.

To do an integer comparison you need ifnum:

ifnum 1=0
1 equals 0.
else
1 is not equal 0.
fi

Also, TeX does not have a not equal to comparison. You can only compare with <, =, or >.

share|improve this answer

edited 18 hours ago

egreg

771k9191 gold badges20132013 silver badges33693369 bronze badges

answered 18 hours ago

Phelype OleinikPhelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

if 11<>0
11 is not equal 0.
else
11 equals 0.
fi

<>0 11 is not equal 0.

ifnum 1=0
1 equals 0.
else
1 is not equal 0.
fi

share|improve this answer

edited 18 hours ago

egreg

771k9191 gold badges20132013 silver badges33693369 bronze badges

answered 18 hours ago

Phelype OleinikPhelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

edited 18 hours ago

egreg

771k9191 gold badges20132013 silver badges33693369 bronze badges

edited 18 hours ago

egreg

771k9191 gold badges20132013 silver badges33693369 bronze badges

answered 18 hours ago

Phelype OleinikPhelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

answered 18 hours ago

Phelype OleinikPhelype Oleinik

34.5k77 gold badges5959 silver badges115115 bronze badges

8

Just for completeness: (La)TeX does have something that is equivalent to <>: unlessifnum#1=#2.

documentclass[]article 
begindocument

unlessifnum1=0
1 is not equal 0.
else
1 equals 0.
fi

enddocument

In this case it does not make things shorter or simpler, but sometimes this helps making the code easier to understand.

share|improve this answer

edited 15 hours ago

answered 16 hours ago

Schrödinger's catSchrödinger's cat

9,5701313 silver badges2828 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This requires LaTeX. The question is tagged "tex-core".
  
  – barbara beeton
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @barbarabeeton Thanks! Corrected. The MWE is clearly LaTeX.
  
  – Schrödinger's cat
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This does not require LaTeX: it requires e-TeX extensions, which, these days, are normally enabled by default. This has probably been a “slip of the tongue” of @barbarabeeton; it is a fact, however, that, since 2015, if I recollect correctly, the LaTeX kernel requires e-TeX extensions.
  
  – GuM
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @GuM -- I accept the fact that this requires e-TeX extensions. However, I still consider "tex-core" to pertain to the original Knuthian TeX, and unless isn't there. (I know. I could have used it more than once.) This limitation is present in the "tex-core" explication: "regardless of extensions (eTeX, etc.)".
  
  – barbara beeton
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @barbarabeeton You could have used it unless it woult not yet have been implemented? ;-)
  
  – Schrödinger's cat
  9 hours ago
  
  

  
  
  
  

 | 
show 2 more comments

8

Just for completeness: (La)TeX does have something that is equivalent to <>: unlessifnum#1=#2.

documentclass[]article 
begindocument

unlessifnum1=0
1 is not equal 0.
else
1 equals 0.
fi

enddocument

In this case it does not make things shorter or simpler, but sometimes this helps making the code easier to understand.

share|improve this answer

edited 15 hours ago

answered 16 hours ago

Schrödinger's catSchrödinger's cat

9,5701313 silver badges2828 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This requires LaTeX. The question is tagged "tex-core".
  
  – barbara beeton
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @barbarabeeton Thanks! Corrected. The MWE is clearly LaTeX.
  
  – Schrödinger's cat
  15 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  This does not require LaTeX: it requires e-TeX extensions, which, these days, are normally enabled by default. This has probably been a “slip of the tongue” of @barbarabeeton; it is a fact, however, that, since 2015, if I recollect correctly, the LaTeX kernel requires e-TeX extensions.
  
  – GuM
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @GuM -- I accept the fact that this requires e-TeX extensions. However, I still consider "tex-core" to pertain to the original Knuthian TeX, and unless isn't there. (I know. I could have used it more than once.) This limitation is present in the "tex-core" explication: "regardless of extensions (eTeX, etc.)".
  
  – barbara beeton
  14 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @barbarabeeton You could have used it unless it woult not yet have been implemented? ;-)
  
  – Schrödinger's cat
  9 hours ago
  
  

  
  
  
  

 | 
show 2 more comments

Just for completeness: (La)TeX does have something that is equivalent to <>: unlessifnum#1=#2.

documentclass[]article 
begindocument

unlessifnum1=0
1 is not equal 0.
else
1 equals 0.
fi

enddocument

In this case it does not make things shorter or simpler, but sometimes this helps making the code easier to understand.

share|improve this answer

edited 15 hours ago

answered 16 hours ago

Schrödinger's catSchrödinger's cat

9,5701313 silver badges2828 bronze badges

documentclass[]article 
begindocument

unlessifnum1=0
1 is not equal 0.
else
1 equals 0.
fi

enddocument

share|improve this answer

edited 15 hours ago

answered 16 hours ago

Schrödinger's catSchrödinger's cat

9,5701313 silver badges2828 bronze badges

answered 16 hours ago

Schrödinger's catSchrödinger's cat

9,5701313 silver badges2828 bronze badges

answered 16 hours ago

Schrödinger's catSchrödinger's cat

9,5701313 silver badges2828 bronze badges