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72 lines
1.5 KiB
72 lines
1.5 KiB
local A, F, I = {}, {}, {}
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local function unwind(stack, sp)
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local x = stack[sp]
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if type(x) == 'table' then
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if x[1] == A then
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stack[sp + 1] = x[2]
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return unwind(stack, sp + 1)
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elseif x[1] == I then
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stack[sp] = x[2]
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return unwind(stack, sp)
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elseif x[1] == F then
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if sp - 1 >= x[3] then
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return x[2](stack, sp)
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else
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error("insufficient arguments for supercombinator " .. x[4])
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end
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end
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return x
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else
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return x, stack, sp
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end
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end
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local function repr(x)
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if type(x) == 'table' then
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if x[1] == A then
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return repr(x[2]) .. '(' .. repr(x[3]) .. ')'
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elseif x[1] == F then
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return x[4]
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elseif x[1] == I then
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return '&' .. repr(x[2])
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end
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local r = {}
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for k, v in pairs(x) do
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r[k] = repr(v)
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end
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return '{' .. table.concat(r, ', ') .. '}'
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else
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return tostring(x)
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end
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end
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local function eval(stack, sp)
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local nf = (unwind({ stack[sp] }, 1))
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stack[sp] = { I, nf }
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return nf
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end
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local function getchar(stack, sp)
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local k = stack[sp - 1][3]; sp = sp - 1
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local knil = stack[sp - 1][3]; sp = sp - 1
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local ch = io.read(1)
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if ch then
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stack[sp] = { A, k, ch:byte() }
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else
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stack[sp] = { A, knil, 0 }
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end
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return unwind(stack, sp)
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end
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local getchar_combinator = { F, getchar, 2 }
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local function putchar()
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local ch = stack[sp - 1][3];
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local k = stack[sp - 2][3]; sp = sp - 1
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io.write(string.char(ch))
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stack[sp] = { A, k, ch }
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return unwind(stack, sp)
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end
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local putchar_combinator = { F, putchar, 2 }
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