121 lines
2.5 KiB
Lua
121 lines
2.5 KiB
Lua
-- Extensions to the table module
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module ("table", package.seeall)
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--require "list" FIXME: allow require loops
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local _sort = sort
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--- Make table.sort return its result.
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-- @param t table
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-- @param c comparator function
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-- @return sorted table
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function sort (t, c)
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_sort (t, c)
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return t
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end
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--- Return whether table is empty.
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-- @param t table
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-- @return <code>true</code> if empty or <code>false</code> otherwise
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function empty (t)
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return not next (t)
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end
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--- Find the number of elements in a table.
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-- @param t table
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-- @return number of elements in t
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function size (t)
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local n = 0
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for _ in pairs (t) do
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n = n + 1
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end
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return n
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end
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--- Make the list of indices of a table.
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-- @param t table
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-- @return list of indices
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function indices (t)
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local u = {}
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for i, v in pairs (t) do
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insert (u, i)
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end
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return u
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end
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--- Make the list of values of a table.
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-- @param t table
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-- @return list of values
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function values (t)
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local u = {}
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for i, v in pairs (t) do
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insert (u, v)
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end
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return u
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end
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--- Invert a table.
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-- @param t table <code>{i=v, ...}</code>
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-- @return inverted table <code>{v=i, ...}</code>
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function invert (t)
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local u = {}
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for i, v in pairs (t) do
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u[v] = i
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end
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return u
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end
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--- Rearrange some indices of a table.
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-- @param m table <code>{old_index=new_index, ...}</code>
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-- @param t table to rearrange
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-- @return rearranged table
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function rearrange (m, t)
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local r = clone (t)
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for i, v in pairs (m) do
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r[v] = t[i]
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r[i] = nil
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end
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return r
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end
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--- Make a shallow copy of a table, including any metatable (for a
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-- deep copy, use tree.clone).
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-- @param t table
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-- @param nometa if non-nil don't copy metatable
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-- @return copy of table
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function clone (t, nometa)
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local u = {}
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if not nometa then
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setmetatable (u, getmetatable (t))
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end
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for i, v in pairs (t) do
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u[i] = v
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end
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return u
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end
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--- Merge two tables.
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-- If there are duplicate fields, u's will be used. The metatable of
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-- the returned table is that of t.
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-- @param t first table
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-- @param u second table
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-- @return merged table
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function merge (t, u)
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local r = clone (t)
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for i, v in pairs (u) do
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r[i] = v
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end
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return r
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end
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--- Make a table with a default value for unset keys.
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-- @param x default entry value (default: <code>nil</code>)
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-- @param t initial table (default: <code>{}</code>)
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-- @return table whose unset elements are x
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function new (x, t)
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return setmetatable (t or {},
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{__index = function (t, i)
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return x
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end})
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end
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