k design scrapheap

scrapheap.k

# Unevaluated

A `wrap attribute that causes overindexing to auto-mod based on length of list.
Avoids mismatch of behaviour of i# and -i#. Cut will auto-fill if not long enough.
Negative indexing wraps backwards: (`wrap"abc")[-1] is "c"
Requires `null to go back to default behaviour?

## Slice as basis for lots of primitives

Inspired by ngn's https://chat.stackexchange.com/transcript/message/59004538#59004538 ...

// cycle

slice:{s:x>0; x+:0&1+x+#y; l:(x#y;x_y); $[s;l;|l]}

s:"supercali"
slice[3;s]
slice[-3;s]
slice[-10;s]
slice[10;s]

cuts:{*+{slice[y;*|x]}\[(();y);x]}
cuts[2 1 3 2;s]
/ what if more than length of string?

""

// non-cycle

slice:{s:x>0; x+:0&1+x+#y; l:(x$y;x_y); $[s;l;|l]}

s:"supercali"
slice[3;s]
slice[-3;s]
slice[-10;s]
slice[10;s]

cuts:{*+{slice[y;*|x]}\[(();y);x]}
cuts[2 1 3 2;s]

// why join/split when we can group?
/ (does not work same for all cases eg "\n\n" as no empty strings)

/ group then filter
{x(=(~a)*1+\a:"\n"=x)_0} "hello\nworld\nhow\nare\nyou\n"
{(=(~a)*x!1+\a:"\n"=x)_0}  / interesting that can't do x!x too early as stops the mask working (since a is a dict)

/ filter then group
{= :[;a]_x!+\a:"\n"=x}
{= :[;a]_+\a:"\n"=x!x}     / self-dict (doesn't quite work yet in ngn/k)
{= :[;.a]_+\a:"\n"=x!x}    / same (works; notice the dot before a to just get values)

how could this be written without 'a'?
could write in a stackish language...
  push to end with "\n"= applied
  push to end based on last elem in stack with +\ applied
  swap last two
  where-not stack based on last elem in stack (removes last elem and filters remaining stack elements)
  group stack based on last element