CODEWITHSUNDEEP
stringvariableslualoadevaluation
mathsbeauty
mathsbeauty

Reputation: 366

Problem with Load function in Lua while execution

print("i", "j", "i & j")
for i = 0,1 do
   for j=0,1 do
   print(i, j, i & j)
   end
end

The above code works fine in Lua. It gives the following output.

i   j   i & j
0   0   0
0   1   0
1   0   0
1   1   1

However the following code doesn't work. Basically I want to generate Truth Table based on some user input. There seems to be issue with load function. Probably it is related with type of variable that function load handles. Can anyone suggest? Can we write Lua function to achieve same? Here is the code that doesn't work.

str="i & j"
print("i", "j", "i & j")
for i = 0,1 do
    for j=0,1 do
        print(i,j,load(str))
    end
end

Upvotes: 0

Views: 446

Answers (2)

Mike V.
Mike V.

Reputation: 2205

use little tricks:

local str="i * j" -- or i & j for v5.3 lua
print("i", "j", str)
for i = 0,1 do
    for j=0,1 do
       local  s = str:gsub("i",i):gsub("j",j)
       print(i,j, (loadstring or load)("return "..s)() )
    end
end

Upvotes: 1

J. А. del Rio - слава СССР
J. А. del Rio - слава СССР

Reputation: 136

Here's an attempt which is supposed to work with a maximum of nearly sixty values:

-- Lua >= 5.3
local concat = table.concat

local str    = "((i | j) ~ k) & l" -- io.read() ?
local sep    = " "

local values = {} -- 0 or 1
-- i, j, k, etc.
local names  = setmetatable({},
  {__index = function(t,k)
    t[k] = 0
    values[#values+1] = k
    return 0
  end}
)

local aux = {} -- Values to be printed
load("return " .. str,nil,"t",names)()  -- Initialization
local n = #values
print(concat(values,sep) .. sep .. str) -- Variables
for i = 0,(1<<n)-1 do -- 2^n evaluations
  local k = i
  for j = n,1,-1 do
    names[values[j]] = k % 2
    aux[j] = k % 2
    k = k >> 1
  end
  print(concat(aux,sep) .. sep .. load("return " .. str,nil,"t",names)())
end

i j k l ((i | j) ~ k) & l
0 0 0 0 0
0 0 0 1 0
0 0 1 0 0
0 0 1 1 1
0 1 0 0 0
0 1 0 1 1
0 1 1 0 0
0 1 1 1 0
1 0 0 0 0
1 0 0 1 1
1 0 1 0 0
1 0 1 1 0
1 1 0 0 0
1 1 0 1 1
1 1 1 0 0
1 1 1 1 0

Upvotes: 2

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