doc/lispintro: Don't mention set (bug#67734)
* doc/lispintro/emacs-lisp-intro.texi (Using set): Delete. (Using setq): Adjust accordingly. (setq): Rename from "set & setq" and don't refer to `set` any more. (Review): Don't mention `set` any more.
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Stefan Monnier
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cb3684e9df
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1 changed files with 49 additions and 84 deletions
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@ -317,7 +317,7 @@ List Processing
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* Evaluation:: Running a program.
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* Variables:: Returning a value from a variable.
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* Arguments:: Passing information to a function.
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* set & setq:: Setting the value of a variable.
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* setq:: Setting the value of a variable.
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* Summary:: The major points.
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* Error Message Exercises::
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@ -358,7 +358,6 @@ Arguments
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Setting the Value of a Variable
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* Using set:: Setting values.
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* Using setq:: Setting a quoted value.
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* Counting:: Using @code{setq} to count.
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@ -1060,7 +1059,7 @@ of Lisp.
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* Evaluation:: Running a program.
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* Variables:: Returning a value from a variable.
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* Arguments:: Passing information to a function.
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* set & setq:: Setting the value of a variable.
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* setq:: Setting the value of a variable.
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* Summary:: The major points.
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* Error Message Exercises::
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@end menu
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@ -1782,7 +1781,7 @@ A symbol can have any value attached to it or, to use the jargon, we can
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string, @code{"such as this"}; to a list, such as @code{(spruce pine
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oak)}; we can even bind a variable to a function definition.
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A symbol can be bound to a value in several ways. @xref{set & setq, ,
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A symbol can be bound to a value in several ways. @xref{setq, ,
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Setting the Value of a Variable}, for information about one way to do
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this.
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@ -2273,52 +2272,52 @@ When your fill column is 70 and you evaluate the expression, the
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message @code{"He saw 38 red foxes leaping."} appears in your echo
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area.
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@node set & setq
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@node setq
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@section Setting the Value of a Variable
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@cindex Variable, setting value
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@cindex Setting value of variable
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@cindex @samp{bind} defined
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There are several ways by which a variable can be given a value. One of
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the ways is to use either the function @code{set} or the special form
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@code{setq}. Another way is to use @code{let} (@pxref{let}). (The
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jargon for this process is to @dfn{bind} a variable to a value.)
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There are several ways by which a variable can be given a value.
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One of the ways is to use the special form @code{setq}. Another way
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is to use @code{let} (@pxref{let}). (The jargon for this process is
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to @dfn{bind} a variable to a value.)
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The following sections not only describe how @code{set} and @code{setq}
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work but also illustrate how arguments are passed.
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The following sections not only describe how @code{setq} works but
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also illustrate how arguments are passed.
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@menu
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* Using set:: Setting values.
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* Using setq:: Setting a quoted value.
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* Using setq:: Setting variables.
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* Counting:: Using @code{setq} to count.
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@end menu
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@node Using set
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@subsection Using @code{set}
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@node Using setq
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@subsection Using @code{setq}
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@findex set
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To set the value of the symbol @code{flowers} to the list @code{'(rose
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To set the value of the symbol @code{flowers} to the list @code{(rose
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violet daisy buttercup)}, evaluate the following expression by
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positioning the cursor after the expression and typing @kbd{C-x C-e}.
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@smallexample
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(set 'flowers '(rose violet daisy buttercup))
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(setq flowers '(rose violet daisy buttercup))
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@end smallexample
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@noindent
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The list @code{(rose violet daisy buttercup)} will appear in the echo
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area. This is what is @emph{returned} by the @code{set} function. As a
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side effect, the symbol @code{flowers} is bound to the list; that is,
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the symbol @code{flowers}, which can be viewed as a variable, is given
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the list as its value. (This process, by the way, illustrates how a
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side effect to the Lisp interpreter, setting the value, can be the
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primary effect that we humans are interested in. This is because every
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Lisp function must return a value if it does not get an error, but it
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will only have a side effect if it is designed to have one.)
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area. This is what is @emph{returned} by the @code{setq} special
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form. As a side effect, the symbol @code{flowers} is bound to the
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list; that is, the symbol @code{flowers}, which can be viewed as
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a variable, is given the list as its value. (This process, by the
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way, illustrates how a side effect to the Lisp interpreter, setting
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the value, can be the primary effect that we humans are interested in.
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This is because every Lisp function must return a value if it does not
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get an error, but it will only have a side effect if it is designed to
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have one.)
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After evaluating the @code{set} expression, you can evaluate the symbol
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@code{flowers} and it will return the value you just set. Here is the
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symbol. Place your cursor after it and type @kbd{C-x C-e}.
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After evaluating the @code{setq} expression, you can evaluate the
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symbol @code{flowers} and it will return the value you just set.
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Here is the symbol. Place your cursor after it and type @kbd{C-x C-e}.
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@smallexample
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flowers
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@ -2336,30 +2335,8 @@ in front of it, what you will see in the echo area is the symbol itself,
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'flowers
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@end smallexample
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Note also, that when you use @code{set}, you need to quote both
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arguments to @code{set}, unless you want them evaluated. Since we do
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not want either argument evaluated, neither the variable
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@code{flowers} nor the list @code{(rose violet daisy buttercup)}, both
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are quoted. (When you use @code{set} without quoting its first
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argument, the first argument is evaluated before anything else is
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done. If you did this and @code{flowers} did not have a value
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already, you would get an error message that the @samp{Symbol's value
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as variable is void}; on the other hand, if @code{flowers} did return
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a value after it was evaluated, the @code{set} would attempt to set
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the value that was returned. There are situations where this is the
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right thing for the function to do; but such situations are rare.)
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@node Using setq
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@subsection Using @code{setq}
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@findex setq
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As a practical matter, you almost always quote the first argument to
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@code{set}. The combination of @code{set} and a quoted first argument
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is so common that it has its own name: the special form @code{setq}.
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This special form is just like @code{set} except that the first argument
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is quoted automatically, so you don't need to type the quote mark
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yourself. Also, as an added convenience, @code{setq} permits you to set
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several different variables to different values, all in one expression.
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Also, as an added convenience, @code{setq} permits you to set several
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different variables to different values, all in one expression.
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To set the value of the variable @code{carnivores} to the list
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@code{'(lion tiger leopard)} using @code{setq}, the following expression
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@ -2369,18 +2346,6 @@ is used:
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(setq carnivores '(lion tiger leopard))
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@end smallexample
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@noindent
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This is exactly the same as using @code{set} except the first argument
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is automatically quoted by @code{setq}. (The @samp{q} in @code{setq}
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means @code{quote}.)
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@need 1250
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With @code{set}, the expression would look like this:
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@smallexample
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(set 'carnivores '(lion tiger leopard))
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@end smallexample
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Also, @code{setq} can be used to assign different values to
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different variables. The first argument is bound to the value
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of the second argument, the third argument is bound to the value of the
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@ -2400,14 +2365,14 @@ to the symbol @code{herbivores}:
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not have fit on a page; and humans find it easier to read nicely
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formatted lists.)
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Although I have been using the term ``assign'', there is another way of
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thinking about the workings of @code{set} and @code{setq}; and that is to
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say that @code{set} and @code{setq} make the symbol @emph{point} to the
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list. This latter way of thinking is very common and in forthcoming
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chapters we shall come upon at least one symbol that has ``pointer'' as
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part of its name. The name is chosen because the symbol has a value,
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specifically a list, attached to it; or, expressed another way,
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the symbol is set to point to the list.
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Although I have been using the term ``assign'', there is another way
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of thinking about the workings of @code{setq}; and that is to say that
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@code{setq} makes the symbol @emph{point} to the list. This latter
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way of thinking is very common and in forthcoming chapters we shall
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come upon at least one symbol that has ``pointer'' as part of its
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name. The name is chosen because the symbol has a value, specifically
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a list, attached to it; or, expressed another way, the symbol is set
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to point to the list.
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@node Counting
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@subsection Counting
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@ -3598,6 +3563,8 @@ and the two are not intended to refer to the same value. The
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@unnumberedsubsec @code{let} Prevents Confusion
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@end ifnottex
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@c FIXME!! lexbind!!
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@cindex @samp{local variable} defined
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@cindex @samp{variable, local}, defined
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The @code{let} special form prevents confusion. @code{let} creates a
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@ -4471,9 +4438,7 @@ number; it will be printed as the character with that @sc{ascii} code.
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The @code{setq} special form sets the value of its first argument to the
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value of the second argument. The first argument is automatically
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quoted by @code{setq}. It does the same for succeeding pairs of
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arguments. Another function, @code{set}, takes only two arguments and
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evaluates both of them before setting the value returned by its first
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argument to the value returned by its second argument.
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arguments.
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@item buffer-name
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Without an argument, return the name of the buffer, as a string.
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@ -16949,15 +16914,15 @@ Here is the line again; how does it work?
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@noindent
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This line is a short, but complete Emacs Lisp expression.
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We are already familiar with @code{setq}. It sets the following variable,
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@code{major-mode}, to the subsequent value, which is @code{text-mode}.
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The single-quote before @code{text-mode} tells Emacs to deal directly
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with the @code{text-mode} symbol, not with whatever it might stand for.
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@xref{set & setq, , Setting the Value of a Variable},
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for a reminder of how @code{setq} works.
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The main point is that there is no difference between the procedure you
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use to set a value in your @file{.emacs} file and the procedure you use
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anywhere else in Emacs.
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We are already familiar with @code{setq}. It sets the following
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variable, @code{major-mode}, to the subsequent value, which is
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@code{text-mode}. The single-quote before @code{text-mode} tells
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Emacs to deal directly with the @code{text-mode} symbol, not with
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whatever it might stand for. @xref{setq, , Setting the Value of
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a Variable}, for a reminder of how @code{setq} works. The main point
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is that there is no difference between the procedure you use to set
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a value in your @file{.emacs} file and the procedure you use anywhere
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else in Emacs.
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@need 800
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Here is the next line:
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