From 9e01bb11a5af844980566d381db2bfa04f512324 Mon Sep 17 00:00:00 2001
From: heav <hheav3@gmail.com>
Date: Mon, 28 Nov 2022 16:35:21 +0000
Subject: made an iterator library.

---
 czzc/init.lua |   6 ++-
 czzc/iter.lua | 153 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 157 insertions(+), 2 deletions(-)
 create mode 100644 czzc/iter.lua

diff --git a/czzc/init.lua b/czzc/init.lua
index eea504b..04759b6 100644
--- a/czzc/init.lua
+++ b/czzc/init.lua
@@ -4,5 +4,7 @@ local function czzc_require(mod)
 end
 
 czzc_require"table"
-czzc_require"string"
-czzc_require"io"
+--czzc_require"string"
+--czzc_require"io"
+czzc_require"iter"
+czzc_require"math"
\ No newline at end of file
diff --git a/czzc/iter.lua b/czzc/iter.lua
new file mode 100644
index 0000000..866b43a
--- /dev/null
+++ b/czzc/iter.lua
@@ -0,0 +1,153 @@
+local M = {}
+
+-- an important thing to keep in mind:
+-- factories often return three values, like ipairs.
+-- the actual function, an "invariant state", and a control variable.
+-- we'll just use closures to encapsulate this behaviour, but ipairs/pairs won't.
+-- as such, functions passing around iterators also ought to pass those around.
+
+-- the idea is that you can map a function over outputs of an iterator.
+-- for example, string.bytes over an iterator over characters of a string.
+-- returns an iterator.
+M.apply = function(fn, iter, ...)
+    return function()
+        local vals = {iter()}
+        if #vals > 0 then
+            -- me when lua versions.
+            return fn((unpack or table.unpack)(vals))
+        end
+    end, ...
+end
+
+-- apply, but only send n arguments of the iterator to the function.
+M.apply_n = function(args_n, fn, iter, ...)
+    return function()
+        local vals = {iter()}
+        if #vals > 0 then
+            local pt1 = {}
+            local pt2 = {}
+            for i=1, args_n do
+                table.insert(pt1, vals[i])
+            end
+            for i=args_n+1, #vals do
+                table.insert(pt2, vals[i])
+            end
+            return fn(table.unpack(pt1)), table.unpack(pt2)
+        end
+    end, ...
+end
+
+-- by factory, i mean a function generating iterators, like ipairs.
+-- this returns a factory.
+-- args_n is how many of the arguments to send to the function maximum, optionally.
+M.apply_factory = function(fn, fact, args_n)
+    if not args_n then
+        return function(...)
+            return M.apply(fn, fact(...))
+        end
+    else
+        return function(...)
+            return M.apply_n(args_n,fn, fact(...))
+        end
+    end
+end
+
+-- only works properly with iterators returning one value for now.
+-- returns an array of all of its results.
+M.collect = function(...)
+    local res = {}
+    for value, _ in ... do
+        table.insert(res, value)
+    end
+    return res
+end
+
+-- works with iterators of up to 8 values.
+-- there seems to be no way to make this generic, sorry.
+-- returns an array of arrays.
+M.multicollect = function(...)
+    local res = {}
+    for v1,v2,v3,v4,v5,v6,v7,v8 in ... do
+        table.insert(res, {v1,v2,v3,v4,v5,v6,v7,v8})
+    end
+    return res
+end
+
+-- gets an iterator's reverse.
+M.reverse = function(...)
+    local res = M.multicollect(...)
+    local i = #res
+    return function()
+        if i>0 then
+            i = i - 1
+            return table.unpack(res[i+1])
+        end
+    end
+end
+
+-- makes an iterator factory output reverses.
+M.reverse_factory = function(factory)
+    return function(...)
+        return M.reverse(factory(...))
+    end
+end
+
+-- alright, enough of these meta functions. time for some cool iterators.
+
+-- returns character, index.
+M.chars = function(str)
+    local i = 1
+    return function()
+        if i <= #str then
+            i = i + 1
+            return str:sub(i-1,i-1), i-1
+        end
+    end
+end
+
+-- returns all words, where words are defined as adjacent non-whitespace.
+-- of the form word, index.
+M.words = function(str)
+    local i = 0
+    local it = str:gmatch("%S+")
+    return function()
+        i = i + 1
+        return it(), i
+    end
+end
+
+-- cool, right?
+M.bytes = M.apply_factory(string.byte, M.chars, 1)
+
+-- iterates over the digits of a natural number starting with the
+-- least significant one. i.e 1003: 3 -> 0 -> 0 -> 1.
+-- returns digit index second, for if it's needed.
+M.digits = function(n)
+    local digit = 0
+    -- i think math.abs is the most reasonable way to handle negatives.
+    n = math.abs(n)
+    return function()
+        -- 0 is a special case since bee.
+        if n ~= 0 and n < 10^digit then return end
+        digit = digit + 1
+        return math.floor(n/10^(digit-1))%10, digit
+    end
+end
+-- the same as above, but from the most significant instead, i.e 1003: 1 -> 0 -> 0 -> 3.
+M.digits_msd = M.reverse_factory(M.digits)
+
+-- iterates over a table in reverse.
+M.ipairs_rev = M.reverse_factory(ipairs)
+
+-- autogenerate reversed variants of certain iterators.
+local to_be_reversed = {
+    "chars",
+    "bytes",
+    "words"
+}
+
+for _, v in ipairs(to_be_reversed) do
+    M[v.."_rev"] = M.reverse_factory(M[v])
+end
+
+return M
\ No newline at end of file
-- 
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