commit ea7a15fba27ea3604d8c52e570bea78b976761c2
parent fdd6d84fc0e72c45c34527b2a6974e5220bd0a87
Author: Wolfgang Corcoran-Mathe <wcm@sigwinch.xyz>
Date: Wed, 31 Jan 2024 23:51:14 -0500
Sequencing & Iteration: Texify.
Diffstat:
1 file changed, 62 insertions(+), 40 deletions(-)
diff --git a/doc/r7rs-small/r7rs-small.texinfo b/doc/r7rs-small/r7rs-small.texinfo
@@ -1979,66 +1979,86 @@ input and output.
@print{} 4 plus 1 equals 5
@end example
+@end deffn
+
Note that there is a third form of @code{begin} used as a library declaration.
@xref{Library syntax}
@node Iteration
@subsection Iteration
-syntax: (do ((@svar{variable1} @svar{init1} @svar{step1})
-@dots{})
-(@svar{test} @svar{expression} @dots{})
-@svar{command} @dots{})
-
-Syntax: All of @svar{init}, @svar{step}, @svar{test}, and @svar{command} are expressions.
-
-Semantics: A do expression is an iteration construct. It specifies a set of variables to be
-bound, how they are to be initialized at the start, and how they are to be updated on each
-iteration. When a termination condition is met, the loop exits after evaluating the
-@svar{expression}s.
-
-A do expression is evaluated as follows: The @svar{init} expressions are evaluated (in some
-unspecified order), the @svar{variable}s are bound to fresh locations, the results of the @svar{init}
-expressions are stored in the bindings of the @svar{variable}s, and then the iteration phase
-begins.
-
-Each iteration begins by evaluating @svar{test}; if the result is false (see section 6.3), then the
-@svar{command} expressions are evaluated in order for effect, the @svar{step} expressions are
-evaluated in some unspecified order, the @svar{variable}s are bound to fresh locations, the
-results of the @svar{step}s are stored in the bindings of the @svar{variable}s, and the next iteration
-begins.
+@c Since @deffn would put this whole complex form on one line in most
+@c output types, I've put the actual syntax after definition header.
+@c Maybe there's a better way?
+@deffn syntax do
-If @svar{test} evaluates to a true value, then the @svar{expression}s are evaluated from left to right
-and the values of the last @svar{expression} are returned. If no @svar{expression}s are present,
-then the value of the do expression is unspecified.
+@format
+@code{(do ((}@svar{variable@sub{1}} @svar{init@sub{1}} @svar{step@sub{1}}@code{)}
+ @dots{}@code{)}
+ @code{(}@svar{test} @svar{expression} @dots{}@code{)}
+ @svar{command} @dots{}@code{)}
+@end format
-The regionof the binding of a @svar{variable} consists of the entire do expression except for
-the @svar{init}s. It is an error for a @svar{variable} to appear more than once in the list of do
-variables.
+Syntax: All of @svar{init}, @svar{step}, @svar{test}, and @svar{command} are expressions.
-A @svar{step} can be omitted, in which case the effect is the same as if (@svar{variable} @svar{init}
-@svar{variable}) had been written instead of (@svar{variable} @svar{init}).
+Semantics:
+A @code{do} expression is an iteration construct. It specifies a set of variables to
+be bound, how they are to be initialized at the start, and how they are
+to be updated on each iteration. When a termination condition is met,
+the loop exits after evaluating the @svar{expression}s.
+
+A @code{do} expression is evaluated as follows:
+The @svar{init} expressions are evaluated (in some unspecified order),
+the @svar{variable}s are bound to fresh locations, the results of the
+@svar{init} expressions are stored in the bindings of the
+@svar{variable}s, and then the iteration phase begins.
+
+Each iteration begins by evaluating @svar{test}; if the result is
+false (@xref{Booleans}), then the @svar{command}
+expressions are evaluated in order for effect, the @svar{step}
+expressions are evaluated in some unspecified order, the
+@svar{variable}s are bound to fresh locations, the results of the
+@svar{step}s are stored in the bindings of the
+@svar{variable}s, and the next iteration begins.
+
+If @svar{test} evaluates to a true value, then the
+@svar{expression}s are evaluated from left to right and the values of
+the last @svar{expression} are returned. If no @svar{expression}s
+are present, then the value of the @code{do} expression is unspecified.
+
+The region of the binding of a @svar{variable}
+consists of the entire @code{do} expression except for the @svar{init}s.
+It is an error for a @svar{variable} to appear more than once in the
+list of @code{do} variables.
+
+A @svar{step} can be omitted, in which case the effect is the
+same as if @code{(}@svar{variable} @svar{init} @svar{variable}@code{)} had
+been written instead of @code{(}@svar{variable} @svar{init}@code{)}.
@example
(do ((vec (make-vector 5))
(i 0 (+ i 1)))
((= i 5) vec)
- (vector-set! vec i i)) @result{} #(0 1 2 3 4)
+ (vector-set! vec i i)) @result{} #(0 1 2 3 4)
(let ((x '(1 3 5 7 9)))
(do ((x x (cdr x))
(sum 0 (+ sum (car x))))
- ((null? x) sum))) @result{} 25
+ ((null? x) sum))) @result{} 25
@end example
-syntax: (let @svar{variable} @svar{bindings} @svar{body})
+@end deffn
-Semantics: ``Named let'' is a variant on the syntax of let which provides a more general
-looping construct than do and can also be used to express recursion. It has the same
-syntax and semantics as ordinary let except that @svar{variable} is bound within @svar{body} to a
-procedure whose formal arguments are the bound variables and whose body is @svar{body}.
-Thus the execution of @svar{body} can be repeated by invoking the procedure named by
-@svar{variable}.
+@deffn syntax let @svar{variable} @svar{bindings} @svar{body}
+
+``Named @code{let}'' is a variant on the syntax of @code{let} which provides
+a more general looping construct than @code{do} and can also be used to express
+recursion.
+It has the same syntax and semantics as ordinary @code{let}
+except that @svar{variable} is bound within @svar{body} to a procedure
+whose formal arguments are the bound variables and whose body is
+@svar{body}. Thus the execution of @svar{body} can be repeated by
+invoking the procedure named by @svar{variable}.
@example
(let loop ((numbers '(3 -2 1 6 -5))
@@ -2053,9 +2073,11 @@ Thus the execution of @svar{body} can be repeated by invoking the procedure name
(loop (cdr numbers)
nonneg
(cons (car numbers) neg)))))
-@result{} ((6 1 3) (-5 -2))
+ @result{} ((6 1 3) (-5 -2))
@end example
+@end deffn
+
@node Delayed evaluation
@subsection Delayed evaluation
