Le 15/06/2011 10:48, David Baelde a écrit :
> Hi Martin,
>
> Using your terminology to clarify, you could write:
>
> On Wed, Jun 15, 2011 at 10:37 AM, Martin Hamant<[email protected]> wrote:
>> out = output.icecast(
>> fallible=true,
>> start=false
>> )
> out =
>> if stream_format == "mp3" then
>> out(%mp3)
>> end
> # here you also need the else branch to say what out becomes if
> stream_format != "mp3".
Yes, as I am using mp3 for testing purpose, I haven't wrote further.
> Perhaps one way to clarify things is to avoid calling "outputs" a
> "global variable" that is "initialized". A definition has only one
> value over the course of its life, it never changes. You may hide it
> in some part of the script with another definition, but this is really
> different:
> x = 1
> if true then
> x = 2
> # here x is 2
> print(x)
> end
> # x is 1 again
> print(x)
> # in the if-then-block, you could as well replace all occurrences of "x" by
> "y"
>
> Your "dyn_sources" is closer to what is usually called a (global)
> variable. It has an initial value (dyn_source = ref<initial value>)
> but its value can change over time (dyn_source :=<new value>).
>
> I know these differences can be confusing. I hope that my explanations
> help you see the difference, which should be useful when writing
> scripts.
>
Gasp this is very hard to me. I understand the life of x in the little
snip you provided.
I think the confusing is about the partial construction.
here, we speak about a definition "out = icecast.output()", that gives a
function out() which is precisely designed to deffer some parameters
definition. (isn't it ?). Which is called "partial application".
I am sorry, you are certainly going to repeat yourself :(
Here is the full first part of my script, I have annotated examples
which works and some don't:
==========
# First, we create a list referencing the dynamic sources:
dyn_sources = ref []
# This is our icecast output.
# It is a partial application: the source needs to be given!
out = output.icecast(
fallible=true,
start=false
)
# Now we write a function to create
# a playlist source and output it.
def create_playlist(uri) =
# The playlist source
param = string.split(separator="\|",uri)
source_device = list.nth(param,0)
stream_host = list.nth(param,1)
stream_port = list.nth(param,2)
stream_password = list.nth(param,3)
stream_id = list.nth(param,4)
stream_genre = list.nth(param,5)
stream_url = list.nth(param,6)
stream_description = list.nth(param,7)
#stream_format = list.nth(param,8)
s = input.alsa(device="#{source_device}")
# metadata telnet handler
s = server.insert_metadata(id="#{stream_id}-meta", s)
# the following doesn't work.
# for testing purpose
#stream_format = "mp3"
#out =
#if stream_format == "mp3" then
# out(%mp3)
#end
# the following works but hey why ?
out =
out(%mp3)
#The following don't work
#out(%mp3)
# The output
output = out(id="#{stream_id}", host="#{stream_host}",
port=int_of_string("#{stream_port}"), password="#{stream_password}",
genre="#{stream_genre}", url="#{stream_url}",
description="#{stream_description}", mount="stream.mp3", protocol="http", s)
(...)
=============
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