[Guile-commits] 01/04: Move fluids, parameters docs nearer to dynamic-wind

[Andy Wingo]

wingo pushed a commit to branch master
in repository guile.

commit 500e4a83e462b6d59daf9e680fa11139455d5812
Author: Andy Wingo <address@hidden>
Date:   Tue Dec 6 21:09:53 2016 +0100

    Move fluids, parameters docs nearer to dynamic-wind
    
    * doc/ref/api-control.texi:
    * doc/ref/api-scheduling.texi: Move fluids and parameters docs.
---
 doc/ref/api-control.texi    |  297 +++++++++++++++++++++++++++++++++++++++++++
 doc/ref/api-scheduling.texi |  297 -------------------------------------------
 2 files changed, 297 insertions(+), 297 deletions(-)

diff --git a/doc/ref/api-control.texi b/doc/ref/api-control.texi
index 5847b25..8b20e3e 100644
--- a/doc/ref/api-control.texi
+++ b/doc/ref/api-control.texi
@@ -21,6 +21,8 @@ flow of Scheme affects C code.
 * Exceptions::                  Throwing and catching exceptions.
 * Error Reporting::             Procedures for signaling errors.
 * Dynamic Wind::                Dealing with non-local entrance/exit.
+* Fluids and Dynamic States::   Dynamic scope building blocks.
+* Parameters::                  A dynamic scope facility.
 * Handling Errors::             How to handle errors in C code.
 * Continuation Barriers::       Protection from non-local control flow.
 @end menu
@@ -1658,6 +1660,301 @@ context is exited, whether normally or non-locally.
 @end deftypefn
 
 
address@hidden Fluids and Dynamic States
address@hidden Fluids and Dynamic States
+
address@hidden fluids
+
+A @emph{fluid} is an object that can store one value per @emph{dynamic
+state}.  Each thread has a current dynamic state, and when accessing a
+fluid, this current dynamic state is used to provide the actual value.
+In this way, fluids can be used for thread local storage.  Additionally,
+the set of current fluid values can be captured by a dynamic state and
+reinstated in some other dynamic extent, possibly in another thread
+even.
+
+Fluids are a building block for implementing dynamically scoped
+variables.  Dynamically scoped variables are useful when you want to set
+a variable to a value during some dynamic extent in the execution of
+your program and have them revert to their original value when the
+control flow is outside of this dynamic extent.  See the description of
address@hidden below for details.
+
+Guile uses fluids to implement parameters (@pxref{Parameters}).  Usually
+you just want to use parameters directly.  However it can be useful to
+know what a fluid is and how it works, so that's what this section is
+about.
+
+New fluids are created with @code{make-fluid} and @code{fluid?} is
+used for testing whether an object is actually a fluid.  The values
+stored in a fluid can be accessed with @code{fluid-ref} and
address@hidden
+
address@hidden {Scheme Procedure} make-fluid [dflt]
address@hidden {C Function} scm_make_fluid ()
address@hidden {C Function} scm_make_fluid_with_default (dflt)
+Return a newly created fluid, whose initial value is @var{dflt}, or
address@hidden if @var{dflt} is not given.
+Fluids are objects that can hold one
+value per dynamic state.  That is, modifications to this value are
+only visible to code that executes with the same dynamic state as
+the modifying code.  When a new dynamic state is constructed, it
+inherits the values from its parent.  Because each thread normally executes
+with its own dynamic state, you can use fluids for thread local storage.
address@hidden deffn
+
address@hidden {Scheme Procedure} make-unbound-fluid
address@hidden {C Function} scm_make_unbound_fluid ()
+Return a new fluid that is initially unbound (instead of being
+implicitly bound to some definite value).
address@hidden deffn
+
address@hidden {Scheme Procedure} fluid? obj
address@hidden {C Function} scm_fluid_p (obj)
+Return @code{#t} if @var{obj} is a fluid; otherwise, return
address@hidden
address@hidden deffn
+
address@hidden {Scheme Procedure} fluid-ref fluid
address@hidden {C Function} scm_fluid_ref (fluid)
+Return the value associated with @var{fluid} in the current
+dynamic root.  If @var{fluid} has not been set, then return
+its default value. Calling @code{fluid-ref} on an unbound fluid produces
+a runtime error.
address@hidden deffn
+
address@hidden {Scheme Procedure} fluid-set! fluid value
address@hidden {C Function} scm_fluid_set_x (fluid, value)
+Set the value associated with @var{fluid} in the current dynamic root.
address@hidden deffn
+
address@hidden {Scheme Procedure} fluid-unset! fluid
address@hidden {C Function} scm_fluid_unset_x (fluid)
+Disassociate the given fluid from any value, making it unbound.
address@hidden deffn
+
address@hidden {Scheme Procedure} fluid-bound? fluid
address@hidden {C Function} scm_fluid_bound_p (fluid)
+Returns @code{#t} if the given fluid is bound to a value, otherwise
address@hidden
address@hidden deffn
+
address@hidden temporarily changes the values of one or more fluids,
+so that the given procedure and each procedure called by it access the
+given values.  After the procedure returns, the old values are restored.
+
address@hidden {Scheme Procedure} with-fluid* fluid value thunk
address@hidden {C Function} scm_with_fluid (fluid, value, thunk)
+Set @var{fluid} to @var{value} temporarily, and call @var{thunk}.
address@hidden must be a procedure with no argument.
address@hidden deffn
+
address@hidden {Scheme Procedure} with-fluids* fluids values thunk
address@hidden {C Function} scm_with_fluids (fluids, values, thunk)
+Set @var{fluids} to @var{values} temporary, and call @var{thunk}.
address@hidden must be a list of fluids and @var{values} must be the
+same number of their values to be applied.  Each substitution is done
+in the order given.  @var{thunk} must be a procedure with no argument.
+It is called inside a @code{dynamic-wind} and the fluids are
+set/restored when control enter or leaves the established dynamic
+extent.
address@hidden deffn
+
address@hidden {Scheme Macro} with-fluids ((fluid value) @dots{}) body1 body2 
@dots{}
+Execute body @var{body1} @var{body2} @dots{}  while each @var{fluid} is
+set to the corresponding @var{value}.  Both @var{fluid} and @var{value}
+are evaluated and @var{fluid} must yield a fluid.  The body is executed
+inside a @code{dynamic-wind} and the fluids are set/restored when
+control enter or leaves the established dynamic extent.
address@hidden deffn
+
address@hidden {C Function} SCM scm_c_with_fluids (SCM fluids, SCM vals, SCM 
(*cproc)(void *), void *data)
address@hidden {C Function} SCM scm_c_with_fluid (SCM fluid, SCM val, SCM 
(*cproc)(void *), void *data)
+The function @code{scm_c_with_fluids} is like @code{scm_with_fluids}
+except that it takes a C function to call instead of a Scheme thunk.
+
+The function @code{scm_c_with_fluid} is similar but only allows one
+fluid to be set instead of a list.
address@hidden deftypefn
+
address@hidden {C Function} void scm_dynwind_fluid (SCM fluid, SCM val)
+This function must be used inside a pair of calls to
address@hidden and @code{scm_dynwind_end} (@pxref{Dynamic
+Wind}).  During the dynwind context, the fluid @var{fluid} is set to
address@hidden
+
+More precisely, the value of the fluid is swapped with a `backup'
+value whenever the dynwind context is entered or left.  The backup
+value is initialized with the @var{val} argument.
address@hidden deftypefn
+
address@hidden {Scheme Procedure} dynamic-state? obj
address@hidden {C Function} scm_dynamic_state_p (obj)
+Return @code{#t} if @var{obj} is a dynamic state object;
+return @code{#f} otherwise.
address@hidden deffn
+
address@hidden {C Procedure} int scm_is_dynamic_state (SCM obj)
+Return non-zero if @var{obj} is a dynamic state object;
+return zero otherwise.
address@hidden deftypefn
+
address@hidden {Scheme Procedure} current-dynamic-state
address@hidden {C Function} scm_current_dynamic_state ()
+Return a snapshot of the current fluid-value associations as a fresh
+dynamic state object.
address@hidden deffn
+
address@hidden {Scheme Procedure} set-current-dynamic-state state
address@hidden {C Function} scm_set_current_dynamic_state (state)
+Set the current dynamic state object to @var{state}
+and return the previous current dynamic state object.
address@hidden deffn
+
address@hidden {Scheme Procedure} with-dynamic-state state proc
address@hidden {C Function} scm_with_dynamic_state (state, proc)
+Call @var{proc} while @var{state} is the current dynamic
+state object.
address@hidden deffn
+
address@hidden {C Procedure} void scm_dynwind_current_dynamic_state (SCM state)
+Set the current dynamic state to @var{state} for the current dynwind
+context.
address@hidden deftypefn
+
address@hidden {C Procedure} {void *} scm_c_with_dynamic_state (SCM state, void 
*(*func)(void *), void *data)
+Like @code{scm_with_dynamic_state}, but call @var{func} with
address@hidden
address@hidden deftypefn
+
address@hidden Parameters
address@hidden Parameters
+
address@hidden SRFI-39
address@hidden parameter object
address@hidden Parameter
+
+A parameter object is a procedure.  Calling it with no arguments returns
+its value.  Calling it with one argument sets the value.
+
address@hidden
+(define my-param (make-parameter 123))
+(my-param) @result{} 123
+(my-param 456)
+(my-param) @result{} 456
address@hidden example
+
+The @code{parameterize} special form establishes new locations for
+parameters, those new locations having effect within the dynamic scope
+of the @code{parameterize} body.  Leaving restores the previous
+locations.  Re-entering (through a saved continuation) will again use
+the new locations.
+
address@hidden
+(parameterize ((my-param 789))
+  (my-param)) @result{} 789
+(my-param) @result{} 456
address@hidden example
+
+Parameters are like dynamically bound variables in other Lisp dialects.
+They allow an application to establish parameter settings (as the name
+suggests) just for the execution of a particular bit of code, restoring
+when done.  Examples of such parameters might be case-sensitivity for a
+search, or a prompt for user input.
+
+Global variables are not as good as parameter objects for this sort of
+thing.  Changes to them are visible to all threads, but in Guile
+parameter object locations are per-thread, thereby truly limiting the
+effect of @code{parameterize} to just its dynamic execution.
+
+Passing arguments to functions is thread-safe, but that soon becomes
+tedious when there's more than a few or when they need to pass down
+through several layers of calls before reaching the point they should
+affect.  And introducing a new setting to existing code is often easier
+with a parameter object than adding arguments.
+
address@hidden {Scheme Procedure} make-parameter init [converter]
+Return a new parameter object, with initial value @var{init}.
+
+If a @var{converter} is given, then a call @code{(@var{converter}
+val)} is made for each value set, its return is the value stored.
+Such a call is made for the @var{init} initial value too.
+
+A @var{converter} allows values to be validated, or put into a
+canonical form.  For example,
+
address@hidden
+(define my-param (make-parameter 123
+                   (lambda (val)
+                     (if (not (number? val))
+                         (error "must be a number"))
+                     (inexact->exact val))))
+(my-param 0.75)
+(my-param) @result{} 3/4
address@hidden example
address@hidden deffn
+
address@hidden {library syntax} parameterize ((param value) @dots{}) body1 
body2 @dots{}
+Establish a new dynamic scope with the given @var{param}s bound to new
+locations and set to the given @var{value}s.  @var{body1} @var{body2}
address@hidden is evaluated in that environment.  The value returned is that of
+last body form.
+
+Each @var{param} is an expression which is evaluated to get the
+parameter object.  Often this will just be the name of a variable
+holding the object, but it can be anything that evaluates to a
+parameter.
+
+The @var{param} expressions and @var{value} expressions are all
+evaluated before establishing the new dynamic bindings, and they're
+evaluated in an unspecified order.
+
+For example,
+
address@hidden
+(define prompt (make-parameter "Type something: "))
+(define (get-input)
+  (display (prompt))
+  ...)
+
+(parameterize ((prompt "Type a number: "))
+  (get-input)
+  ...)
address@hidden example
address@hidden deffn
+
+Parameter objects are implemented using fluids (@pxref{Fluids and
+Dynamic States}), so each dynamic state has its own parameter
+locations.  That includes the separate locations when outside any
address@hidden form.  When a parameter is created it gets a
+separate initial location in each dynamic state, all initialized to the
+given @var{init} value.
+
+New code should probably just use parameters instead of fluids, because
+the interface is better.  But for migrating old code or otherwise
+providing interoperability, Guile provides the @code{fluid->parameter}
+procedure:
+
address@hidden {Scheme Procedure} fluid->parameter fluid [conv]
+Make a parameter that wraps a fluid.
+
+The value of the parameter will be the same as the value of the fluid.
+If the parameter is rebound in some dynamic extent, perhaps via
address@hidden, the new value will be run through the optional
address@hidden procedure, as with any parameter.  Note that unlike
address@hidden, @var{conv} is not applied to the initial value.
address@hidden deffn
+
+As alluded to above, because each thread usually has a separate dynamic
+state, each thread has its own locations behind parameter objects, and
+changes in one thread are not visible to any other.  When a new dynamic
+state or thread is created, the values of parameters in the originating
+context are copied, into new locations.
+
address@hidden SRFI-39
+Guile's parameters conform to SRFI-39 (@pxref{SRFI-39}).
+
+
 @node Handling Errors
 @subsection How to Handle Errors
 
diff --git a/doc/ref/api-scheduling.texi b/doc/ref/api-scheduling.texi
index 615e8b6..7ab6210 100644
--- a/doc/ref/api-scheduling.texi
+++ b/doc/ref/api-scheduling.texi
@@ -13,8 +13,6 @@
 * Atomics::                     Atomic references.
 * Mutexes and Condition Variables:: Synchronization primitives.
 * Blocking::                    How to block properly in guile mode.
-* Fluids and Dynamic States::   Thread-local variables, etc.
-* Parameters::                  Dynamic scoping in Scheme.
 * Futures::                     Fine-grain parallelism.
 * Parallel Forms::              Parallel execution of forms.
 @end menu
@@ -665,301 +663,6 @@ delivery of an async causes this function to be 
interrupted.
 @end deftypefn
 
 
address@hidden Fluids and Dynamic States
address@hidden Fluids and Dynamic States
-
address@hidden fluids
-
-A @emph{fluid} is an object that can store one value per @emph{dynamic
-state}.  Each thread has a current dynamic state, and when accessing a
-fluid, this current dynamic state is used to provide the actual value.
-In this way, fluids can be used for thread local storage.  Additionally,
-the set of current fluid values can be captured by a dynamic state and
-reinstated in some other dynamic extent, possibly in another thread
-even.
-
-Fluids are a building block for implementing dynamically scoped
-variables.  Dynamically scoped variables are useful when you want to set
-a variable to a value during some dynamic extent in the execution of
-your program and have them revert to their original value when the
-control flow is outside of this dynamic extent.  See the description of
address@hidden below for details.
-
-Guile uses fluids to implement parameters (@pxref{Parameters}).  Usually
-you just want to use parameters directly.  However it can be useful to
-know what a fluid is and how it works, so that's what this section is
-about.
-
-New fluids are created with @code{make-fluid} and @code{fluid?} is
-used for testing whether an object is actually a fluid.  The values
-stored in a fluid can be accessed with @code{fluid-ref} and
address@hidden
-
address@hidden {Scheme Procedure} make-fluid [dflt]
address@hidden {C Function} scm_make_fluid ()
address@hidden {C Function} scm_make_fluid_with_default (dflt)
-Return a newly created fluid, whose initial value is @var{dflt}, or
address@hidden if @var{dflt} is not given.
-Fluids are objects that can hold one
-value per dynamic state.  That is, modifications to this value are
-only visible to code that executes with the same dynamic state as
-the modifying code.  When a new dynamic state is constructed, it
-inherits the values from its parent.  Because each thread normally executes
-with its own dynamic state, you can use fluids for thread local storage.
address@hidden deffn
-
address@hidden {Scheme Procedure} make-unbound-fluid
address@hidden {C Function} scm_make_unbound_fluid ()
-Return a new fluid that is initially unbound (instead of being
-implicitly bound to some definite value).
address@hidden deffn
-
address@hidden {Scheme Procedure} fluid? obj
address@hidden {C Function} scm_fluid_p (obj)
-Return @code{#t} if @var{obj} is a fluid; otherwise, return
address@hidden
address@hidden deffn
-
address@hidden {Scheme Procedure} fluid-ref fluid
address@hidden {C Function} scm_fluid_ref (fluid)
-Return the value associated with @var{fluid} in the current
-dynamic root.  If @var{fluid} has not been set, then return
-its default value. Calling @code{fluid-ref} on an unbound fluid produces
-a runtime error.
address@hidden deffn
-
address@hidden {Scheme Procedure} fluid-set! fluid value
address@hidden {C Function} scm_fluid_set_x (fluid, value)
-Set the value associated with @var{fluid} in the current dynamic root.
address@hidden deffn
-
address@hidden {Scheme Procedure} fluid-unset! fluid
address@hidden {C Function} scm_fluid_unset_x (fluid)
-Disassociate the given fluid from any value, making it unbound.
address@hidden deffn
-
address@hidden {Scheme Procedure} fluid-bound? fluid
address@hidden {C Function} scm_fluid_bound_p (fluid)
-Returns @code{#t} if the given fluid is bound to a value, otherwise
address@hidden
address@hidden deffn
-
address@hidden temporarily changes the values of one or more fluids,
-so that the given procedure and each procedure called by it access the
-given values.  After the procedure returns, the old values are restored.
-
address@hidden {Scheme Procedure} with-fluid* fluid value thunk
address@hidden {C Function} scm_with_fluid (fluid, value, thunk)
-Set @var{fluid} to @var{value} temporarily, and call @var{thunk}.
address@hidden must be a procedure with no argument.
address@hidden deffn
-
address@hidden {Scheme Procedure} with-fluids* fluids values thunk
address@hidden {C Function} scm_with_fluids (fluids, values, thunk)
-Set @var{fluids} to @var{values} temporary, and call @var{thunk}.
address@hidden must be a list of fluids and @var{values} must be the
-same number of their values to be applied.  Each substitution is done
-in the order given.  @var{thunk} must be a procedure with no argument.
-It is called inside a @code{dynamic-wind} and the fluids are
-set/restored when control enter or leaves the established dynamic
-extent.
address@hidden deffn
-
address@hidden {Scheme Macro} with-fluids ((fluid value) @dots{}) body1 body2 
@dots{}
-Execute body @var{body1} @var{body2} @dots{}  while each @var{fluid} is
-set to the corresponding @var{value}.  Both @var{fluid} and @var{value}
-are evaluated and @var{fluid} must yield a fluid.  The body is executed
-inside a @code{dynamic-wind} and the fluids are set/restored when
-control enter or leaves the established dynamic extent.
address@hidden deffn
-
address@hidden {C Function} SCM scm_c_with_fluids (SCM fluids, SCM vals, SCM 
(*cproc)(void *), void *data)
address@hidden {C Function} SCM scm_c_with_fluid (SCM fluid, SCM val, SCM 
(*cproc)(void *), void *data)
-The function @code{scm_c_with_fluids} is like @code{scm_with_fluids}
-except that it takes a C function to call instead of a Scheme thunk.
-
-The function @code{scm_c_with_fluid} is similar but only allows one
-fluid to be set instead of a list.
address@hidden deftypefn
-
address@hidden {C Function} void scm_dynwind_fluid (SCM fluid, SCM val)
-This function must be used inside a pair of calls to
address@hidden and @code{scm_dynwind_end} (@pxref{Dynamic
-Wind}).  During the dynwind context, the fluid @var{fluid} is set to
address@hidden
-
-More precisely, the value of the fluid is swapped with a `backup'
-value whenever the dynwind context is entered or left.  The backup
-value is initialized with the @var{val} argument.
address@hidden deftypefn
-
address@hidden {Scheme Procedure} dynamic-state? obj
address@hidden {C Function} scm_dynamic_state_p (obj)
-Return @code{#t} if @var{obj} is a dynamic state object;
-return @code{#f} otherwise.
address@hidden deffn
-
address@hidden {C Procedure} int scm_is_dynamic_state (SCM obj)
-Return non-zero if @var{obj} is a dynamic state object;
-return zero otherwise.
address@hidden deftypefn
-
address@hidden {Scheme Procedure} current-dynamic-state
address@hidden {C Function} scm_current_dynamic_state ()
-Return a snapshot of the current fluid-value associations as a fresh
-dynamic state object.
address@hidden deffn
-
address@hidden {Scheme Procedure} set-current-dynamic-state state
address@hidden {C Function} scm_set_current_dynamic_state (state)
-Set the current dynamic state object to @var{state}
-and return the previous current dynamic state object.
address@hidden deffn
-
address@hidden {Scheme Procedure} with-dynamic-state state proc
address@hidden {C Function} scm_with_dynamic_state (state, proc)
-Call @var{proc} while @var{state} is the current dynamic
-state object.
address@hidden deffn
-
address@hidden {C Procedure} void scm_dynwind_current_dynamic_state (SCM state)
-Set the current dynamic state to @var{state} for the current dynwind
-context.
address@hidden deftypefn
-
address@hidden {C Procedure} {void *} scm_c_with_dynamic_state (SCM state, void 
*(*func)(void *), void *data)
-Like @code{scm_with_dynamic_state}, but call @var{func} with
address@hidden
address@hidden deftypefn
-
address@hidden Parameters
address@hidden Parameters
-
address@hidden SRFI-39
address@hidden parameter object
address@hidden Parameter
-
-A parameter object is a procedure.  Calling it with no arguments returns
-its value.  Calling it with one argument sets the value.
-
address@hidden
-(define my-param (make-parameter 123))
-(my-param) @result{} 123
-(my-param 456)
-(my-param) @result{} 456
address@hidden example
-
-The @code{parameterize} special form establishes new locations for
-parameters, those new locations having effect within the dynamic scope
-of the @code{parameterize} body.  Leaving restores the previous
-locations.  Re-entering (through a saved continuation) will again use
-the new locations.
-
address@hidden
-(parameterize ((my-param 789))
-  (my-param)) @result{} 789
-(my-param) @result{} 456
address@hidden example
-
-Parameters are like dynamically bound variables in other Lisp dialects.
-They allow an application to establish parameter settings (as the name
-suggests) just for the execution of a particular bit of code, restoring
-when done.  Examples of such parameters might be case-sensitivity for a
-search, or a prompt for user input.
-
-Global variables are not as good as parameter objects for this sort of
-thing.  Changes to them are visible to all threads, but in Guile
-parameter object locations are per-thread, thereby truly limiting the
-effect of @code{parameterize} to just its dynamic execution.
-
-Passing arguments to functions is thread-safe, but that soon becomes
-tedious when there's more than a few or when they need to pass down
-through several layers of calls before reaching the point they should
-affect.  And introducing a new setting to existing code is often easier
-with a parameter object than adding arguments.
-
address@hidden {Scheme Procedure} make-parameter init [converter]
-Return a new parameter object, with initial value @var{init}.
-
-If a @var{converter} is given, then a call @code{(@var{converter}
-val)} is made for each value set, its return is the value stored.
-Such a call is made for the @var{init} initial value too.
-
-A @var{converter} allows values to be validated, or put into a
-canonical form.  For example,
-
address@hidden
-(define my-param (make-parameter 123
-                   (lambda (val)
-                     (if (not (number? val))
-                         (error "must be a number"))
-                     (inexact->exact val))))
-(my-param 0.75)
-(my-param) @result{} 3/4
address@hidden example
address@hidden deffn
-
address@hidden {library syntax} parameterize ((param value) @dots{}) body1 
body2 @dots{}
-Establish a new dynamic scope with the given @var{param}s bound to new
-locations and set to the given @var{value}s.  @var{body1} @var{body2}
address@hidden is evaluated in that environment.  The value returned is that of
-last body form.
-
-Each @var{param} is an expression which is evaluated to get the
-parameter object.  Often this will just be the name of a variable
-holding the object, but it can be anything that evaluates to a
-parameter.
-
-The @var{param} expressions and @var{value} expressions are all
-evaluated before establishing the new dynamic bindings, and they're
-evaluated in an unspecified order.
-
-For example,
-
address@hidden
-(define prompt (make-parameter "Type something: "))
-(define (get-input)
-  (display (prompt))
-  ...)
-
-(parameterize ((prompt "Type a number: "))
-  (get-input)
-  ...)
address@hidden example
address@hidden deffn
-
-Parameter objects are implemented using fluids (@pxref{Fluids and
-Dynamic States}), so each dynamic state has its own parameter
-locations.  That includes the separate locations when outside any
address@hidden form.  When a parameter is created it gets a
-separate initial location in each dynamic state, all initialized to the
-given @var{init} value.
-
-New code should probably just use parameters instead of fluids, because
-the interface is better.  But for migrating old code or otherwise
-providing interoperability, Guile provides the @code{fluid->parameter}
-procedure:
-
address@hidden {Scheme Procedure} fluid->parameter fluid [conv]
-Make a parameter that wraps a fluid.
-
-The value of the parameter will be the same as the value of the fluid.
-If the parameter is rebound in some dynamic extent, perhaps via
address@hidden, the new value will be run through the optional
address@hidden procedure, as with any parameter.  Note that unlike
address@hidden, @var{conv} is not applied to the initial value.
address@hidden deffn
-
-As alluded to above, because each thread usually has a separate dynamic
-state, each thread has its own locations behind parameter objects, and
-changes in one thread are not visible to any other.  When a new dynamic
-state or thread is created, the values of parameters in the originating
-context are copied, into new locations.
-
address@hidden SRFI-39
-Guile's parameters conform to SRFI-39 (@pxref{SRFI-39}).
-
-
 @node Futures
 @subsection Futures
 @cindex futures