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  1. local translators = { }
  2.  
  3. local function translate(expr)
  4. 	return translators[expr.expr_type](expr)
  5. end
  6.  
  7. function translators.var(expr)
  8. 	return { text = expr.name, locals = { } }
  9. end
  10.  
  11. function translators.abs(expr)
  12. 	local param = expr.param
  13. 	local body = translate(expr.body)
  14. 	local text = "function(" .. param .. ")\n"
  15. 	for i, local_ in ipairs(body.locals) do
  16. 		text = text .. local_
  17. 	end
  18. 	text = text .. "return " .. body.text .. "\nend"
  19. 	return { text = text, locals = { } }
  20. end
  21.  
  22. function translators.app(expr)
  23. 	local fn = translate(expr.fn)
  24. 	local arg = translate(expr.arg)
  25. 	local text = "(" .. fn.text .. ")(" .. arg.text .. ")"
  26. 	local locals = { }
  27. 	for i, local_ in ipairs(fn.locals) do
  28. 		table.insert(locals, local_)
  29. 	end
  30. 	for i, local_ in ipairs(arg.locals) do
  31. 		table.insert(locals, local_)
  32. 	end
  33. 	return { text = text, locals = locals }
  34. end
  35.  
  36. function translators.let(expr)
  37. 	local value = translate(expr.value)
  38. 	local body = translate(expr.body)
  39. 	local local_ = "local " .. expr.name .. " = " .. value.text .. "\n"
  40. 	local locals = { }
  41. 	table.insert(locals, local_)
  42. 	for i, local_ in ipairs(value.locals) do
  43. 		table.insert(locals, local_)
  44. 	end
  45. 	for i, local_ in ipairs(body.locals) do
  46. 		table.insert(locals, local_)
  47. 	end
  48. 	return { text = body.text, locals = locals }
  49. end
  50.  
  51. function translators.str(expr)
  52. 	return { text = string.format("%q", expr.value), locals = { } }
  53. end
  54.  
  55. local optimizers = { }
  56.  
  57. local function optimize(expr)
  58. 	return optimizers[expr.expr_type](expr)
  59. end
  60.  
  61. function optimizers.var(expr)
  62. 	return expr
  63. end
  64.  
  65. function optimizers.abs(expr)
  66. 	return {
  67. 		expr_type = "abs",
  68. 		param = expr.param,
  69. 		body = optimize(expr.body),
  70. 	}
  71. end
  72.  
  73. function optimizers.app(expr)
  74. 	if expr.fn.expr_type == "abs" then
  75. 		return optimize({
  76. 			expr_type = "let",
  77. 			name = expr.fn.param,
  78. 			value = optimize(expr.arg),
  79. 			body = optimize(expr.fn.body),
  80. 		})
  81. 	else
  82. 		return {
  83. 			expr_type = "app",
  84. 			fn = optimize(expr.fn),
  85. 			arg = optimize(expr.arg),
  86. 		}
  87. 	end
  88. end
  89.  
  90. function optimizers.let(expr)
  91. 	return {
  92. 		expr_type = "let",
  93. 		name = expr.name,
  94. 		value = optimize(expr.value),
  95. 		body = optimize(expr.body),
  96. 	}
  97. end
  98.  
  99. function optimizers.str(expr)
  100. 	return expr
  101. end
  102.  
  103. local expr = {
  104. 	expr_type = "abs",
  105. 	param = "_",
  106. 	body = {
  107. 		expr_type = "app",
  108. 		fn = {
  109. 			expr_type = "abs",
  110. 			param = "x",
  111. 			body = {
  112. 				expr_type = "app",
  113. 				fn = {
  114. 					expr_type = "abs",
  115. 					param = "y",
  116. 					body = { expr_type = "var", name = "y" },
  117. 				},
  118. 				arg = { expr_type = "var", name = "x" },
  119. 			},
  120. 		},
  121. 		arg = { expr_type = "str", value = "Hello, world!" },
  122. 	},
  123. }
  124.  
  125. print("-- unoptimized")
  126. print(translate(expr).text)
  127.  
  128. print("-- optimized")
  129. print(translate(optimize(expr)).text)
  130.  
Success #stdin #stdout 0s 2836KB
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Standard input is empty
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-- unoptimized
function(_)
return (function(x)
return (function(y)
return y
end)(x)
end)("Hello, world!")
end
-- optimized
function(_)
local x = "Hello, world!"
local y = x
return y
end
https://ideone.com/YegTLr
language:
Lua (luac 5.3.3)
created:
10 years ago
visibility:
secret

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