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| -rw-r--r-- | gtwiwtg.lisp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/gtwiwtg.lisp b/gtwiwtg.lisp index c273680..88e820c 100644 --- a/gtwiwtg.lisp +++ b/gtwiwtg.lisp @@ -427,6 +427,26 @@ CONCAT! MODIFIES AND RETURNS ITS FIRST ARGUMENT." (defun merge! (comparator gen1 gen2 &rest gens) + "Emulates the behavior of MERGE (in the ANSI standard), but for generators. + +The emulation is not perfect, but it holds in the following sense: If +all the inputs are sorted according to COMPARATOR then the output will +also be sorted according to COMPARATOR. + +The generator created through a merge has a length that is maximal +among the lengths of the arguments to MERGE!. Hence, if any of the +arguments is an infinite generator, then the merged generator is also +infinite. + +An example: + +> (collect (merge! #'< + (times 4) + (range :from 4 :to 10 :by 2) + (range :from -10 :to 28 :by 6))) + + (-10 -4 0 1 2 2 3 4 6 8 8 14 20 26) +" (let ((all-gens (list* gen1 gen2 gens))) (assert (all-good all-gens)) |