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## defered through the event-loop.
#
## Programing with futures is explicit continuation-passing-style.
# ### ### ### ######### ######### #########
## Requisites
package require Debug
package require Debug::snit
package require debug
package require debug::caller
package require snit
# ### ### ### ######### ######### #########
## Narrative tracing
Debug off future
#Debug on future
Debug prefix future {[list [Debug::snit::call]] }
Debug.future {}
debug.future {}
set future [$type create %AUTO%]
if {[llength $args]} { $future {*}$args }
return $future
}
# Provide a new future in default configuration and trigger it to
# return the args and the next idle point. Further configuration
# can be done on the result object.
typemethod return {args} {
Debug.future {}
debug.future {}
set f [$type new]
after idle [list $f return {*}$args]
return $f
}
# ### ### ### ######### ######### #########
## API. Various configuration methods. Chainable.
# Configure callback to invoke on `return`.
method {on return} {cmdprefix args} {
Debug.future {}
debug.future {}
set myOkCmdPrefix $cmdprefix
if {[llength $args]} { $self {*}$args }
return $self
}
# Configure callback to invoke on `error`.
method {on error} {cmdprefix args} {
Debug.future {}
debug.future {}
set myErrorCmdPrefix $cmdprefix
if {[llength $args]} { $self {*}$args }
return $self
}
# Clear all callbacks. The future will now swallow all its invokations.
method nop {} {
Debug.future {}
debug.future {}
set myOkCmdPrefix {}
set myErrorCmdPrefix {}
return
}
# Same as nop.
method empty {} {
Debug.future {}
debug.future {}
set myOkCmdPrefix {}
set myErrorCmdPrefix {}
return
}
# Configure callbacks to post invokations to the other future.
method chain {future args} {
Debug.future {}
debug.future {}
# Inlined on return on error configuration chaining to another
# future.
set myOkCmdPrefix [list $future return]
set myErrorCmdPrefix [list $future error]
if {[llength $args]} { $self {*}$args }
return $self
}
# ### ### ### ######### ######### #########
## API. Invoke the future. This will destroy the instance as well.
method error {message} {
Debug.future {}
debug.future {}
$self Error $message
return
}
method return {args} {
Debug.future {}
debug.future {}
# Syntax: | 0
# : -code x | 2
# : -code x val | 3
# : val | 4
# Allowing multiple -code settings, last one is taken.
set rcode 0
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# ### ### ### ######### ######### #########
## Destruction. A user is not allowed to destroy instances. Can
## only be done by invoking it (return or error), as part of which
## it destroys itself.
destructor {
Debug.future {}
debug.future {}
if {$myIsDone} return
return -code error "Illegal attempt to destroy unresolved future \"$self\""
}
# ### ### ### ######### ######### #########
## State
variable myIsDone 0
variable myOkCmdPrefix {return -code return}
variable myErrorCmdPrefix {return -code error}
# ### ### ### ######### ######### #########
## Helper commands. Invoke the configured callbacks, if any. This
## is also where the instance destroys itself. Note that callback
## execution is defered to the event loop.
method Ok {result} {
Debug.future {[list ==> $myOkCmdPrefix]}
debug.future {[list ==> $myOkCmdPrefix]}
set cmdprefix $myOkCmdPrefix
DestroySelf
if {![llength $cmdprefix]} return
after 0 [list {*}$cmdprefix $result]
return
}
method Error {message} {
Debug.future {[list ==> $myErrorCmdPrefix]}
debug.future {[list ==> $myErrorCmdPrefix]}
set cmdprefix $myErrorCmdPrefix
DestroySelf
if {![llength $cmdprefix]} return
after 0 [list {*}$cmdprefix $message]
return
}
proc DestroySelf {} {
debug.future {}
upvar 1 self self myIsDone myIsDone
set myIsDone 1
$self destroy
return
}
##
|