The many uses of @ in PicoLisp

The AT-mark @ is everywhere in PicoLisp source code, and sometimes it is not obvious, at least for beginners, what the meaning of @ in the context at hand is.

Here is a list that summarizes all uses of @ in PicoLisp, giving examples and explanations, as well as links to related docs with more information. It is probably necessary to read the docs first to understand the compact information in the list. This summary serves only as a quick overview, helping to find out the context and meaning of an otherwise mysterious @ mark in some PicoLisp code.

All (?) possible uses of @ with examples and explanations

• CAR of a lambda expression (Evaluation > "when the CAR is the symbol @")

(de foo @ ...)

All arguments are evaluated and kept internally in a list


• read-eval-loops (@ Result > load)

(- @ @@ @@@)

The result of the last (3) evaluation(s) stored in the VAL of symbol


• Flow- and logic functions with conditional expressions (@ Result > Flow functions)

(while (read)
	(println @))

(and
	@
	(min @ 5)
	(prinl @)
	(gt0 (dec @)) )

Stores result of (the last) conditional expression


• Flow- and logic functions with controlling expressions (@ Result > Flow functions)

(case @ ("^M" NIL)
	("^J" "^M")
	(T @))

Stores result of controlling expression


• 'match' and 'fill' (Function reference > match)

(match '(@A Zeit) '(Keine))

Pattern wildcard


• 'text' (Function reference > text)

(text "abc @1 def @2" 'XYZ 123)

Replaces all occurrences of an at-mark "@", followed by one of the letters "1" through "9", and "A" through "Z", with the corresponding any argument


• Path names (Invocation)

(load "@lib/misc.l")

Home directory substitution


• Pilog, variable (Pilog)

(be likes (John @X))

Pilog variable


• Pilog, anonymous variable (Pilog)

(be likes (John @))

Anonymous Pilog variable


• Shared object libraries (Function reference > native)

(native "@" "getenv" 'S "TERM")

64-bit version only Calls a native C function. The first argument should specify a shared object library, e.g. "@", here a transient symbol that stands for the current main program

http://picolisp.com/wiki/?atmark

03jan19

abu