sequences.extras: Add each-prior and map-prior

[factor.git] / extra / sequences / extras / extras.factor

diff --git a/extra/sequences/extras/extras.factor b/extra/sequences/extras/extras.factor
index 24561f91460863cbd2daa829e5fb54385b1e0588..f47ebc56508934065d8e4552fe9df11cd3efa84e 100644 (file)
--- a/extra/sequences/extras/extras.factor
+++ b/extra/sequences/extras/extras.factor
@@ -800,3 +800,26 @@ INSTANCE: step-slice virtual-sequence
         new-resizable
         [ [ push ] curry compose 3nested-each ] keep
     ] keep like ; inline
+
+: each-prior ( ... seq quot: ( ... prior elt -- ... ) -- ... )
+    '[ [ swap @ ] keep ]
+    sequence-operator 0 -rot each-integer-from drop ; inline
+
+: map-prior-as ( ... seq quot: ( ... prior elt -- elt' ) exemplar -- seq' )
+    [
+        '[ [ swap @ ] keep swap ] length-operator 0 -rot
+    ] dip map-integers-as nip ; inline
+
+: map-prior ( ... seq quot: ( ... prior elt -- elt' ) -- seq' )
+    over map-prior-as ; inline
+
+TUPLE: virtual-zip-index seq ;
+
+C: <zip-index> virtual-zip-index
+
+M: virtual-zip-index length seq>> length ; inline
+
+M: virtual-zip-index nth-unsafe
+    over [ seq>> nth-unsafe ] [ 2array ] bi* ; inline
+
+INSTANCE: virtual-zip-index immutable-sequence