Re: [Caml-list] [ANN] OCamp - Reactive programming in the shell

[Anthony Tavener <anthony.tavener@gmail.com>]

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Hah! You were serious? I thought with commands like hipp and stir, and your
legal review notice at the end, that this was an April Fool's joke. :)

On Thu, Apr 2, 2015 at 12:38 PM, Frédéric Bour <frederic.bour@lakaban.net>
wrote:

> Code is finally available at:
>     https://github.com/def-lkb/ocamp
>
> Sorry for the little delay!
>
>
> On 01/04/2015 22:32, Frédéric Bour wrote:
>
>> OCamp extends unix shells with constructions to express memoization,
>> sharing of computations and reactive programming.
>>
>> # Subcommands
>>
>> ## fire
>>
>> Just wrap a unix command with "ocamp fire" to enable the extension:
>>   $ ocamp fire bash
>>
>> This will spawn a new bash session where the following subcommands are
>> enabled.
>>
>> ## hipp
>>
>>   $ ocamp hipp <command>
>>
>> Will memoize the output and exit status of <command>.
>> Later calls to the same <command> won't lead to actual execution, but
>> just to a duplication of its previous output.
>> Concurrent calls to <command> will just share the same process, the
>> beginning of the output being replayed to later callers.
>>
>> The identity of a command is defined by its arguments and working
>> directory.
>>
>> ## stir
>>
>>   $ ocamp stir <command>
>>
>> Indicate potential changes in the output if <command> was rerun.
>> Later calls to `hipp` will recompute <command> as if it was not yet
>> memoized.
>>
>> ## (un)follow
>>
>>   $ ocamp follow <command>
>>
>> First, <command> is memoized if it was not the case yet.
>> Then changes to dependencies of <command> will trigger a reevaluation.
>> Use `stir` to notify a change.
>>
>> (to follow is an hipp/stir reactivity).
>>
>> ## pull
>>
>>   $ ocamp pull <command>
>>
>> Closely related to `hipp`, but instead of marking dependency on the
>> output of <command>, the dependency applies to the "effects" of <command>.
>>
>> Thus, if `stir` is used:
>> - all pullers will be reevaluated.
>> - hippers will be reevaluated only if the output is different.
>>
>> ## Summary
>>
>>   $ ocamp fire <command> - setup a new session alive until <command> exits
>>           pull <command> - mark dependency on effects of <command>
>>           hipp <command> - mark dependency on output of <command>
>>           stir <command> - notify that <command> might have been updated
>>           follow <command> - eval <command>, and reactively recompute it
>>                              whenever one of its dependencies change.
>>           unfollow <command> - stop recomputing <command> when
>> dependencies
>>                                change
>>
>> hipp and pull provide memoization.
>> stir and follow bring a flavor of reactive programming.
>>
>> # Examples
>>
>> ## Fibonacci
>>
>>   $ cat fib.sh
>>   #!/bin/sh
>>   ARG="$1"
>>   if [ "$ARG" -le 1 ]; then
>>     echo "$ARG"
>>   else
>>     A=`ocamp hipp ./fib.sh $((ARG-1))`
>>     B=`ocamp hipp ./fib.sh $((ARG-2))`
>>     echo $((A+B))
>>   fi
>>
>>   $ time ocamp fire ./fib.sh 50
>>   12586269025
>>     real    0m0.391s
>>   user    0m0.153s
>>   sys     0m0.060s
>>
>> ## Build-system
>>
>> `ocamp` provides simple primitives to construct and manage a dependency
>> graph.
>>
>> This might be a saner foundation to base a build-system on than make(1):
>> - the command focus on one specific problem
>> - no dsl is involved; rules can be plain unix commands, including a
>> shell, rather than a make-flavored simulation of shell
>> - nothing is provided for resolving goals; indeed this is better left to
>> tools specifically built for goal-search.
>>
>> A quick'n'dirty script building ocamp itself is provided as an example.
>>
>> # Future
>>
>> The current release is a proof-of-concept and should be considered alpha
>> quality.
>> The two features planned next are a way to make the graph persistent (all
>> data is kept in memory atm) and an interface to debug and/or observe graph
>> construction.
>>
>> Note: code is undergoing legal review and should be available soon \o/
>>
>>
>
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