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------------------------------------------------------------------------------
-- util.lua
-- Lua utilities.
------------------------------------------------------------------------------
util = { }
function util.subclass(parent)
-- parent should have no-arg constructor.
local subclass = parent:new()
subclass.super = parent
-- Not strictly necessary - parent constructor should do this.
subclass.__index = subclass
return subclass
end
function util.identity(x)
return x
end
function util.catlist(...)
local res = { }
local tables = { ... }
if #tables == 1 then
return tables[1]
else
for _, tab in ipairs(tables) do
for _, val in ipairs(tab) do
table.insert(res, val)
end
end
end
return res
end
function util.cathash(...)
local res = { }
local tables = { ... }
if #tables == 1 then
return tables[1]
else
for _, tab in ipairs(tables) do
for key, val in ipairs(tab) do
res[key] = val
end
end
end
return res
end
-- Classic map, but discards nil values (table.insert doesn't like nil).
function util.map(fn, ...)
local lists = { ... }
local res = { }
if #lists == 0 then
return res
elseif #lists == 1 then
for _, val in ipairs(lists[1]) do
local nval = fn(val)
if nval ~= nil then
table.insert(res, nval)
end
end
else
for i = 1, #lists[1] do
local args = { }
for _, list in ipairs(lists) do
if not list[i] then
break
end
table.insert(args, list[i])
end
if #args < #lists then
break
end
local nval = fn(unpack(args))
if nval ~= nil then
table.insert(res, nval)
end
end
end
return res
end
function util.filter(fn, list)
local res = { }
for _, val in ipairs(list) do
if fn(val) then
table.insert(res, val)
end
end
return res
end
function util.forall(list, pred)
for _, value in ipairs(list) do
if not pred(value) then
return false
end
end
return true
end
function util.exists(list, pred)
for _, value in ipairs(list) do
if pred(value) then
return true
end
end
return false
end
function util.random_from(list)
return list[ crawl.random2(#list) + 1 ]
end
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