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  1. -- Remove values from array when predicate is true. (1.01)
  2. -- @see foUKZx
  3.  
  4. function remove_if(a, pred)
  5.     local n = #a
  6.     local k = 1
  7.     -- Find first matching.
  8.     while k <= n and not pred(a[k]) do
  9.         k = k + 1
  10.     end
  11.     -- Copy non-matching.
  12.     local last = k-1
  13.     for k = k+1, n do
  14.         if not pred(a[k]) then
  15.             last = last + 1
  16.             a[last] = a[k]
  17.         end
  18.     end
  19.     -- Clear empty.
  20.     for k = last+1, n do
  21.         a[k] = nil
  22.     end
  23.     assert(#a == last)
  24. end
  25.  
  26. -- Testing.
  27.  
  28. local a = {11,22,33,44,55}
  29. print('a:size:'..#a)
  30. for k, v in ipairs(a) do
  31.     print('a:'..k, v)
  32. end
  33.  
  34. -- Remove even.
  35. remove_if(a, function (v) return v%2 == 0 end)
  36. print('b:size:'..#a)
  37. for k, v in ipairs(a) do
  38.     print('b:'..k, v)
  39. end
  40.  
  41. -- Remove odd.
  42. remove_if(a, function (v) return v%2 == 1 end)
  43. print('c:size:'..#a)
  44. for k, v in ipairs(a) do
  45.     print('c:'..k, v)
  46. end
Success #stdin #stdout 0.01s 5404KB
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stdin
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Standard input is empty
stdout
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a:size:5
a:1	11
a:2	22
a:3	33
a:4	44
a:5	55
b:size:3
b:1	11
b:2	33
b:3	55
c:size:0
https://ideone.com/nAO6X5
language:
Lua (luac 5.3.3)
created:
1 year ago
visibility:
public

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