Hi!
I can't understand why the first of these is working while the second isn't (with error $2: argument number out of range)
test_route_object.pd

Because only messages beginning with a float as first atom are implicitely handled as lists by puredata.
If you suppress this first atom with [route], you get a message with 2 atoms, the first being treated as a selector, and the second as a float.
This message is handled as a message --like, for example, the message [ set 1( -- , not as a list.
You must prepend the "list" selector to further process it as a list : just insert a [list] object after the output of [route].

And if you print the output of the pack on the left, you'll see that it prepends "list" to [samplerate 44100(

ok, I get it! it is working now...
thank you both!

well, I really have trouble with data types in PD: how can I write simple text? I want to write log messages that I can print to the console (without backslashes!), through the network, and maybe to a text file.
| messages like this are seen as lists, right? (

@rph-r Yes, that will be a list...... and "messages" will be the selector followed by 'like' 'this' etc. as symbols.
[rawprint] is a useful external to analyse formats.
This should help...... concat.zip
Sending [symbol( into the right inlet of [concat] before passing the message will turn the whole message (including the selector) into a single symbol, keeping the spaces between the original atoms.
I am pretty sure that it was made by @jameslo...... but I could be mistaken...
The comma in your message will always be interpreted as "new message" though.

The MrPeach library has an external [str] which can manipulate different message
formats in many ways.
And the old cxc library from Pd extended..
cxc was updated for 64-bit Pd by Lucarda in 2018 (for windows and maybe for other os's)....
.....very useful for string manipulation in Pd.
David.