pd/doc/1.manual/x2.htm

  2.6.5. dollar signs

In message or object boxes, message arguments starting with a dollar sign and a number (like "$1" or "$3-bazoo") are variables which are substituted with values supplied as part of the environment the message is passed in. In the case of message boxes, the environment consists of the arguments of the "list" message (possibly extrapolated from "bang," "float," or other) that the message box is responding to. Thus, if a message box gets "23 skidoo" and if it contains the text, "$2 until $1," out comes the message, "skidoo until 23."

Object boxes contain text which forms a message to be sent to Pd to create and initialize the object. Here, $1, etc., are taken from the context in which the patch was loaded. When the patch is a new document or opened from a file the "$" variables are undefined. But if the patch is an abstraction (see the next section) they are taken from the abstractions' creation arguments.

Constructions such as "$1-x" are expanded by string concatenation. This is the mechanism for making local variables. In particular, $0 in an abstraction is a counter which is guaranteed to be unique to that abstraction, so sends and receives with names like "$0-bear" can be used as local send/receive pairs.

Note that the expansion of variables such as $0 and $1 only works at the beginning of the symbol; so, for instance, "rats-$1" will not be expanded. Occasionally you may want to have double or triple substitutions; this can be done one stage at a time by nesting abstractions (with each subpatch adding its own $-variable to the beginning of a symbol and passing that on as argument to a further abstraction.)

For example, if you want to get dog-food, dog-ears, and cat-food, for example, have an abstraction "a1" that invokes an abstraction "a2" twice, as "a2 $1-food" and "a2 $1-ears", and then in a third patch call a1 twice, as "a1 cat" and "a1 dog". Inside the four "a2" copioes, $1 will evaluate to "dog-food", "cat-food", "dog-ears", and "cat-ears".

daniel wrote:

hi list

is there a place where I can read about the use of 0$- names?

thanx in advance

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