DeleteCases does not work with EvenQ? While `Select` works fine

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up vote
1
down vote

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EvenQ[FromDigits /@ Tuples[2, 3, 5, 7, 5]]

Works fine. But

DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], EvenQ]
DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], _EvenQ]

does not seem to be deleting any Even numbers as expected?

What am I doing wrong?

In comparison,

Select[FromDigits /@ Tuples[2, 3, 5, 7, 5], OddQ]

Works perfectly fine!!

MMA: 11.3 X64 (Win)

filtering conditional

share|improve this question

asked 1 hour ago

Chen Stats Yu

2,5211335

add a comment | 

up vote
1
down vote

favorite

EvenQ[FromDigits /@ Tuples[2, 3, 5, 7, 5]]

Works fine. But

DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], EvenQ]
DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], _EvenQ]

does not seem to be deleting any Even numbers as expected?

What am I doing wrong?

In comparison,

Select[FromDigits /@ Tuples[2, 3, 5, 7, 5], OddQ]

Works perfectly fine!!

MMA: 11.3 X64 (Win)

filtering conditional

share|improve this question

asked 1 hour ago

Chen Stats Yu

2,5211335

add a comment | 

up vote
1
down vote

favorite

up vote
1
down vote

favorite

EvenQ[FromDigits /@ Tuples[2, 3, 5, 7, 5]]

Works fine. But

DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], EvenQ]
DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], _EvenQ]

does not seem to be deleting any Even numbers as expected?

What am I doing wrong?

In comparison,

Select[FromDigits /@ Tuples[2, 3, 5, 7, 5], OddQ]

Works perfectly fine!!

MMA: 11.3 X64 (Win)

filtering conditional

share|improve this question

asked 1 hour ago

Chen Stats Yu

2,5211335

EvenQ[FromDigits /@ Tuples[2, 3, 5, 7, 5]]

Works fine. But

DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], EvenQ]
DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], _EvenQ]

does not seem to be deleting any Even numbers as expected?

What am I doing wrong?

In comparison,

Select[FromDigits /@ Tuples[2, 3, 5, 7, 5], OddQ]

Works perfectly fine!!

MMA: 11.3 X64 (Win)

filtering conditional

filtering conditional

share|improve this question

asked 1 hour ago

Chen Stats Yu

2,5211335

share|improve this question

asked 1 hour ago

Chen Stats Yu

2,5211335

share|improve this question

share|improve this question

asked 1 hour ago

Chen Stats Yu

2,5211335

asked 1 hour ago

Chen Stats Yu

2,5211335

asked 1 hour ago

Chen Stats Yu

2,5211335

2,5211335

add a comment | 

add a comment | 

1 Answer
1

active

oldest

votes

up vote
4
down vote



accepted

For the selection criterion, Select uses a (pure) function, while *Cases uses a pattern. Code below works.

DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], _?EvenQ]

share|improve this answer

edited 57 mins ago

answered 58 mins ago

Αλέξανδρος Ζεγγ

2,6541826

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I cannot believe it's such a simple tweak!! The examples in the documentation is not any more useful than your answer! THANKS!
  – Chen Stats Yu
  58 mins ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @Chen: the thing to remember is that the second argument of Cases/DeleteCases is always a pattern, while for Select, the second argument is an expression test. So, Cases[(* stuff *), EvenQ] actually means "take everything that matches the symbol EvenQ", while Cases[(* stuff *), _?EvenQ] (and Cases[(* stuff *), n_ /; EvenQ[n]] as well) read as "take everything that gives True when EvenQ is applied", which was what was wanted.
  – J. M. is computer-less♦
  32 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  You can see the difference by evaluating Cases[8, EvenQ, EvenQ], Cases[8, EvenQ, _?EvenQ].
  – J. M. is computer-less♦
  29 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @J.M.iscomputer-less good point
  – Î‘λέξανδρος Ζεγγ
  24 mins ago
  

  
  
  
  

add a comment | 

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

active

oldest

votes

active

oldest

votes

up vote
4
down vote



accepted

For the selection criterion, Select uses a (pure) function, while *Cases uses a pattern. Code below works.

DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], _?EvenQ]

share|improve this answer

edited 57 mins ago

answered 58 mins ago

Αλέξανδρος Ζεγγ

2,6541826

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I cannot believe it's such a simple tweak!! The examples in the documentation is not any more useful than your answer! THANKS!
  – Chen Stats Yu
  58 mins ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @Chen: the thing to remember is that the second argument of Cases/DeleteCases is always a pattern, while for Select, the second argument is an expression test. So, Cases[(* stuff *), EvenQ] actually means "take everything that matches the symbol EvenQ", while Cases[(* stuff *), _?EvenQ] (and Cases[(* stuff *), n_ /; EvenQ[n]] as well) read as "take everything that gives True when EvenQ is applied", which was what was wanted.
  – J. M. is computer-less♦
  32 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  You can see the difference by evaluating Cases[8, EvenQ, EvenQ], Cases[8, EvenQ, _?EvenQ].
  – J. M. is computer-less♦
  29 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @J.M.iscomputer-less good point
  – Î‘λέξανδρος Ζεγγ
  24 mins ago
  

  
  
  
  

add a comment | 

up vote
4
down vote



accepted

For the selection criterion, Select uses a (pure) function, while *Cases uses a pattern. Code below works.

DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], _?EvenQ]

share|improve this answer

edited 57 mins ago

answered 58 mins ago

Αλέξανδρος Ζεγγ

2,6541826

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I cannot believe it's such a simple tweak!! The examples in the documentation is not any more useful than your answer! THANKS!
  – Chen Stats Yu
  58 mins ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @Chen: the thing to remember is that the second argument of Cases/DeleteCases is always a pattern, while for Select, the second argument is an expression test. So, Cases[(* stuff *), EvenQ] actually means "take everything that matches the symbol EvenQ", while Cases[(* stuff *), _?EvenQ] (and Cases[(* stuff *), n_ /; EvenQ[n]] as well) read as "take everything that gives True when EvenQ is applied", which was what was wanted.
  – J. M. is computer-less♦
  32 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  You can see the difference by evaluating Cases[8, EvenQ, EvenQ], Cases[8, EvenQ, _?EvenQ].
  – J. M. is computer-less♦
  29 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @J.M.iscomputer-less good point
  – Î‘λέξανδρος Ζεγγ
  24 mins ago
  

  
  
  
  

add a comment | 

up vote
4
down vote



accepted

up vote
4
down vote



accepted

For the selection criterion, Select uses a (pure) function, while *Cases uses a pattern. Code below works.

DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], _?EvenQ]

share|improve this answer

edited 57 mins ago

answered 58 mins ago

Αλέξανδρος Ζεγγ

2,6541826

For the selection criterion, Select uses a (pure) function, while *Cases uses a pattern. Code below works.

DeleteCases[FromDigits /@ Tuples[2, 3, 5, 7, 5], _?EvenQ]

share|improve this answer

edited 57 mins ago

answered 58 mins ago

Αλέξανδρος Ζεγγ

2,6541826

share|improve this answer

share|improve this answer

edited 57 mins ago

edited 57 mins ago

edited 57 mins ago

answered 58 mins ago

Αλέξανδρος Ζεγγ

2,6541826

answered 58 mins ago

Αλέξανδρος Ζεγγ

2,6541826

answered 58 mins ago

Αλέξανδρος Ζεγγ

2,6541826

2,6541826

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I cannot believe it's such a simple tweak!! The examples in the documentation is not any more useful than your answer! THANKS!
  – Chen Stats Yu
  58 mins ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @Chen: the thing to remember is that the second argument of Cases/DeleteCases is always a pattern, while for Select, the second argument is an expression test. So, Cases[(* stuff *), EvenQ] actually means "take everything that matches the symbol EvenQ", while Cases[(* stuff *), _?EvenQ] (and Cases[(* stuff *), n_ /; EvenQ[n]] as well) read as "take everything that gives True when EvenQ is applied", which was what was wanted.
  – J. M. is computer-less♦
  32 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  You can see the difference by evaluating Cases[8, EvenQ, EvenQ], Cases[8, EvenQ, _?EvenQ].
  – J. M. is computer-less♦
  29 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @J.M.iscomputer-less good point
  – Î‘λέξανδρος Ζεγγ
  24 mins ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I cannot believe it's such a simple tweak!! The examples in the documentation is not any more useful than your answer! THANKS!
  – Chen Stats Yu
  58 mins ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  @Chen: the thing to remember is that the second argument of Cases/DeleteCases is always a pattern, while for Select, the second argument is an expression test. So, Cases[(* stuff *), EvenQ] actually means "take everything that matches the symbol EvenQ", while Cases[(* stuff *), _?EvenQ] (and Cases[(* stuff *), n_ /; EvenQ[n]] as well) read as "take everything that gives True when EvenQ is applied", which was what was wanted.
  – J. M. is computer-less♦
  32 mins ago
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  You can see the difference by evaluating Cases[8, EvenQ, EvenQ], Cases[8, EvenQ, _?EvenQ].
  – J. M. is computer-less♦
  29 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  @J.M.iscomputer-less good point
  – Î‘λέξανδρος Ζεγγ
  24 mins ago
  

  
  
  
  

I cannot believe it's such a simple tweak!! The examples in the documentation is not any more useful than your answer! THANKS!
– Chen Stats Yu
58 mins ago

I cannot believe it's such a simple tweak!! The examples in the documentation is not any more useful than your answer! THANKS!
– Chen Stats Yu
58 mins ago

2

2

@Chen: the thing to remember is that the second argument of Cases/DeleteCases is always a pattern, while for Select, the second argument is an expression test. So, Cases[(* stuff *), EvenQ] actually means "take everything that matches the symbol EvenQ", while Cases[(* stuff *), _?EvenQ] (and Cases[(* stuff *), n_ /; EvenQ[n]] as well) read as "take everything that gives True when EvenQ is applied", which was what was wanted.
– J. M. is computer-less♦
32 mins ago

@Chen: the thing to remember is that the second argument of Cases/DeleteCases is always a pattern, while for Select, the second argument is an expression test. So, Cases[(* stuff *), EvenQ] actually means "take everything that matches the symbol EvenQ", while Cases[(* stuff *), _?EvenQ] (and Cases[(* stuff *), n_ /; EvenQ[n]] as well) read as "take everything that gives True when EvenQ is applied", which was what was wanted.
– J. M. is computer-less♦
32 mins ago

1

1

You can see the difference by evaluating Cases[8, EvenQ, EvenQ], Cases[8, EvenQ, _?EvenQ].
– J. M. is computer-less♦
29 mins ago

You can see the difference by evaluating Cases[8, EvenQ, EvenQ], Cases[8, EvenQ, _?EvenQ].
– J. M. is computer-less♦
29 mins ago

@J.M.iscomputer-less good point
– Î‘λέξανδρος Ζεγγ
24 mins ago

@J.M.iscomputer-less good point
– Î‘λέξανδρος Ζεγγ
24 mins ago

add a comment | 

 

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