Baptiste Daroussin
88 lines
2.5 KiB
Lua
88 lines
2.5 KiB
Lua
-- Minimal functional programming utilities.
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-- Written by Gary V. Vaughan, 2015
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--
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-- Copyright(C) 2015-2022 Gary V. Vaughan
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--
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-- Permission is hereby granted, free of charge, to any person obtaining
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-- a copy of this software and associated documentation files(the
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-- "Software"), to deal in the Software without restriction, including
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-- without limitation the rights to use, copy, modify, merge, publish,
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-- distribute, sublicense, and/or sell copies of the Software, and to
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-- permit persons to whom the Software is furnished to do so, subject to
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-- the following conditions:
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--
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-- The above copyright notice and this permission notice shall be
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-- included in all copies or substantial portions of the Software.
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--
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-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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-- EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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-- MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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-- IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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-- CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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-- TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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-- SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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--- @module lyaml.functional
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--- `lyaml.null` value.
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-- @table NULL
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local NULL = setmetatable({}, {_type='LYAML null'})
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--- `lyaml.null` predicate.
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-- @param x operand
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-- @treturn bool `true` if *x* is `lyaml.null`.
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local function isnull(x)
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return(getmetatable(x) or {})._type == 'LYAML null'
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end
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--- Callable predicate.
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-- @param x operand
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-- @treturn bool `true` if *x* is a function has a __call metamethod
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-- @usage r = iscallable(x) and x(...)
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local function iscallable(x)
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if type(x) ~= 'function' then
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x =(getmetatable(x) or {}).__call
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end
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if type(x) == 'function' then
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return x
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end
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end
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--- Compose a function to try each callable with supplied args.
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-- @tparam table fns list of functions to try
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-- @treturn function a new function to call *...* functions, stopping
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-- and returning the first non-nil result, if any
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local function anyof(fns)
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return function(...)
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for _, fn in ipairs(fns) do
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if iscallable(fn) then
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local r = fn(...)
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if r ~= nil then
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return r
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end
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end
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end
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end
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end
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--- Return arguments unchanged.
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-- @param ... arguments
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-- @return *...*
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local function id(...)
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return ...
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end
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--- @export
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return {
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NULL = NULL,
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anyof = anyof,
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id = id,
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iscallable = iscallable,
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isnull = isnull,
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}
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