Meaning of “value is t”
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When using describe-variable, often the value for a variable is listed as:
Its value is t
What does that mean and why specifically t?
help
edited Feb 14 at 17:08
Drew
48.6k463107
asked Feb 14 at 12:39
ChaimKutChaimKut
1127
add a comment |
When using describe-variable, often the value for a variable is listed as:
Its value is t
What does that mean and why specifically t?
help
edited Feb 14 at 17:08
Drew
48.6k463107
asked Feb 14 at 12:39
ChaimKutChaimKut
1127
add a comment |
When using describe-variable, often the value for a variable is listed as:
Its value is t
What does that mean and why specifically t?
help
edited Feb 14 at 17:08
Drew
48.6k463107
asked Feb 14 at 12:39
ChaimKutChaimKut
1127
When using describe-variable, often the value for a variable is listed as:
Its value is t
What does that mean and why specifically t?
help
help
edited Feb 14 at 17:08
Drew
48.6k463107
asked Feb 14 at 12:39
ChaimKutChaimKut
1127
edited Feb 14 at 17:08
Drew
48.6k463107
asked Feb 14 at 12:39
ChaimKutChaimKut
1127
edited Feb 14 at 17:08
Drew
48.6k463107
edited Feb 14 at 17:08
Drew
48.6k463107
edited Feb 14 at 17:08
Drew
48.6k463107
48.6k463107
asked Feb 14 at 12:39
ChaimKutChaimKut
1127
asked Feb 14 at 12:39
ChaimKutChaimKut
1127
asked Feb 14 at 12:39
ChaimKutChaimKut
1127
1127
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
To quote the Emacs Lisp Manual,
t is the preferred way to represent the truth value true. When you
need to choose a value that represents true, and there is no other
basis for choosing, use t. The symbol t always has the value t.
t stands for "True".
This is important because it is used for decision making. It is used in decisions such as "If this condition is true, do this. Otherwise, do that." The statement Its value is t means that the variable you're describing holds the value t. The consequence of the variable being t depends on the variable.
For example,
(setq inhibit-startup-message t)
When the value of inhibit-startup-message is t, Emacs doesn't show the startup screen. To enable the startup screen, you would use a nil value. nil is the opposite of t and means "False".
Generally speaking, the concepts of t and nil are part of what's called Boolean Algebra, a method of logic named after mathematician George Boole.
Boolean Algebra is a topic important to computer programming, and many, many other fields of study. It's also quite fun and interesting. Unfortunately, it's too broad to explain in detail here.
edited Feb 14 at 14:05
NickD
2,6691515
answered Feb 14 at 13:18
Lorem IpsumLorem Ipsum
1,296413
2
I think it's important to explain the "and there is no other basis for choosing" part of the quote -- in elisp, absolutely every value other thannilis considered true for the purposes of boolean tests. Hence you will see the term "non-nil" used a great deal in elisp documentation, asnilis false, and every non-nilvalue is true.tis a value which is true, and which has no other meaning.
– phils
Feb 15 at 4:36
add a comment |
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1 Answer
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1 Answer
1
active
oldest
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votes
To quote the Emacs Lisp Manual,
t is the preferred way to represent the truth value true. When you
need to choose a value that represents true, and there is no other
basis for choosing, use t. The symbol t always has the value t.
t stands for "True".
This is important because it is used for decision making. It is used in decisions such as "If this condition is true, do this. Otherwise, do that." The statement Its value is t means that the variable you're describing holds the value t. The consequence of the variable being t depends on the variable.
For example,
(setq inhibit-startup-message t)
When the value of inhibit-startup-message is t, Emacs doesn't show the startup screen. To enable the startup screen, you would use a nil value. nil is the opposite of t and means "False".
Generally speaking, the concepts of t and nil are part of what's called Boolean Algebra, a method of logic named after mathematician George Boole.
Boolean Algebra is a topic important to computer programming, and many, many other fields of study. It's also quite fun and interesting. Unfortunately, it's too broad to explain in detail here.
edited Feb 14 at 14:05
NickD
2,6691515
answered Feb 14 at 13:18
Lorem IpsumLorem Ipsum
1,296413
2
I think it's important to explain the "and there is no other basis for choosing" part of the quote -- in elisp, absolutely every value other thannilis considered true for the purposes of boolean tests. Hence you will see the term "non-nil" used a great deal in elisp documentation, asnilis false, and every non-nilvalue is true.tis a value which is true, and which has no other meaning.
– phils
Feb 15 at 4:36
add a comment |
To quote the Emacs Lisp Manual,
t is the preferred way to represent the truth value true. When you
need to choose a value that represents true, and there is no other
basis for choosing, use t. The symbol t always has the value t.
t stands for "True".
This is important because it is used for decision making. It is used in decisions such as "If this condition is true, do this. Otherwise, do that." The statement Its value is t means that the variable you're describing holds the value t. The consequence of the variable being t depends on the variable.
For example,
(setq inhibit-startup-message t)
When the value of inhibit-startup-message is t, Emacs doesn't show the startup screen. To enable the startup screen, you would use a nil value. nil is the opposite of t and means "False".
Generally speaking, the concepts of t and nil are part of what's called Boolean Algebra, a method of logic named after mathematician George Boole.
Boolean Algebra is a topic important to computer programming, and many, many other fields of study. It's also quite fun and interesting. Unfortunately, it's too broad to explain in detail here.
edited Feb 14 at 14:05
NickD
2,6691515
answered Feb 14 at 13:18
Lorem IpsumLorem Ipsum
1,296413
2
I think it's important to explain the "and there is no other basis for choosing" part of the quote -- in elisp, absolutely every value other thannilis considered true for the purposes of boolean tests. Hence you will see the term "non-nil" used a great deal in elisp documentation, asnilis false, and every non-nilvalue is true.tis a value which is true, and which has no other meaning.
– phils
Feb 15 at 4:36
add a comment |
To quote the Emacs Lisp Manual,
t is the preferred way to represent the truth value true. When you
need to choose a value that represents true, and there is no other
basis for choosing, use t. The symbol t always has the value t.
t stands for "True".
This is important because it is used for decision making. It is used in decisions such as "If this condition is true, do this. Otherwise, do that." The statement Its value is t means that the variable you're describing holds the value t. The consequence of the variable being t depends on the variable.
For example,
(setq inhibit-startup-message t)
When the value of inhibit-startup-message is t, Emacs doesn't show the startup screen. To enable the startup screen, you would use a nil value. nil is the opposite of t and means "False".
Generally speaking, the concepts of t and nil are part of what's called Boolean Algebra, a method of logic named after mathematician George Boole.
Boolean Algebra is a topic important to computer programming, and many, many other fields of study. It's also quite fun and interesting. Unfortunately, it's too broad to explain in detail here.
edited Feb 14 at 14:05
NickD
2,6691515
answered Feb 14 at 13:18
Lorem IpsumLorem Ipsum
1,296413
To quote the Emacs Lisp Manual,
t is the preferred way to represent the truth value true. When you
need to choose a value that represents true, and there is no other
basis for choosing, use t. The symbol t always has the value t.
t stands for "True".
This is important because it is used for decision making. It is used in decisions such as "If this condition is true, do this. Otherwise, do that." The statement Its value is t means that the variable you're describing holds the value t. The consequence of the variable being t depends on the variable.
For example,
(setq inhibit-startup-message t)
When the value of inhibit-startup-message is t, Emacs doesn't show the startup screen. To enable the startup screen, you would use a nil value. nil is the opposite of t and means "False".
Generally speaking, the concepts of t and nil are part of what's called Boolean Algebra, a method of logic named after mathematician George Boole.
Boolean Algebra is a topic important to computer programming, and many, many other fields of study. It's also quite fun and interesting. Unfortunately, it's too broad to explain in detail here.
edited Feb 14 at 14:05
NickD
2,6691515
answered Feb 14 at 13:18
Lorem IpsumLorem Ipsum
1,296413
edited Feb 14 at 14:05
NickD
2,6691515
edited Feb 14 at 14:05
NickD
2,6691515
edited Feb 14 at 14:05
NickD
2,6691515
2,6691515
answered Feb 14 at 13:18
Lorem IpsumLorem Ipsum
1,296413
answered Feb 14 at 13:18
Lorem IpsumLorem Ipsum
1,296413
answered Feb 14 at 13:18
Lorem IpsumLorem Ipsum
1,296413
1,296413
2
I think it's important to explain the "and there is no other basis for choosing" part of the quote -- in elisp, absolutely every value other thannilis considered true for the purposes of boolean tests. Hence you will see the term "non-nil" used a great deal in elisp documentation, asnilis false, and every non-nilvalue is true.tis a value which is true, and which has no other meaning.
– phils
Feb 15 at 4:36
add a comment |
2
I think it's important to explain the "and there is no other basis for choosing" part of the quote -- in elisp, absolutely every value other thannilis considered true for the purposes of boolean tests. Hence you will see the term "non-nil" used a great deal in elisp documentation, asnilis false, and every non-nilvalue is true.tis a value which is true, and which has no other meaning.
– phils
Feb 15 at 4:36
2
2
I think it's important to explain the "and there is no other basis for choosing" part of the quote -- in elisp, absolutely every value other than
nil is considered true for the purposes of boolean tests. Hence you will see the term "non-nil" used a great deal in elisp documentation, as nil is false, and every non-nil value is true. t is a value which is true, and which has no other meaning.– phils
Feb 15 at 4:36
I think it's important to explain the "and there is no other basis for choosing" part of the quote -- in elisp, absolutely every value other than
nil is considered true for the purposes of boolean tests. Hence you will see the term "non-nil" used a great deal in elisp documentation, as nil is false, and every non-nil value is true. t is a value which is true, and which has no other meaning.– phils
Feb 15 at 4:36
add a comment |
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