JaeHyoLee's solution to Diamond on the Lua track

Instructions

Test suite

Solution

The diamond kata takes as its input a letter, and outputs it in a diamond shape. Given a letter, it prints a diamond starting with 'A', with the supplied letter at the widest point.

Requirements

The first row contains one 'A'.
The last row contains one 'A'.
All rows, except the first and last, have exactly two identical letters.
All rows have as many trailing spaces as leading spaces. (This might be 0).
The diamond is horizontally symmetric.
The diamond is vertically symmetric.
The diamond has a square shape (width equals height).
The letters form a diamond shape.
The top half has the letters in ascending order.
The bottom half has the letters in descending order.
The four corners (containing the spaces) are triangles.

Examples

In the following examples, spaces are indicated by · characters.

Diamond for letter 'A':

Diamond for letter 'C':

··A··
·B·B·
C···C
·B·B·
··A··

Diamond for letter 'E':

····A····
···B·B···
··C···C··
·D·····D·
E·······E
·D·····D·
··C···C··
···B·B···
····A····

Running the tests

To run the tests, run the command busted from within the exercise directory.

Further information

For more detailed information about the Lua track, including how to get help if you're having trouble, please visit the exercism.io Lua language page.

Source

Seb Rose http://claysnow.co.uk/recycling-tests-in-tdd/

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

diamond_spec.lua

local diamond = require 'diamond'

describe('diamond', function()
  it('should generate the diamond for A', function()
    assert.are.equal('A\n', diamond('A'))
  end)

  it('should generate the diamond for B', function()
    local expected =
      ' A \n' ..
      'B B\n' ..
      ' A \n'

    assert.are.equal(expected, diamond('B'))
  end)

  it('should generate the diamond for C', function()
    local expected =
      '  A  \n' ..
      ' B B \n' ..
      'C   C\n' ..
      ' B B \n' ..
      '  A  \n'

    assert.are.equal(expected, diamond('C'))
  end)

  it('should generate the diamond for E', function()
    local expected =
      '    A    \n' ..
      '   B B   \n' ..
      '  C   C  \n' ..
      ' D     D \n' ..
      'E       E\n' ..
      ' D     D \n' ..
      '  C   C  \n' ..
      '   B B   \n' ..
      '    A    \n'

    assert.are.equal(expected, diamond('E'))
  end)

  it('should generate the diamond for H', function()
    local expected =
      '       A       \n' ..
      '      B B      \n' ..
      '     C   C     \n' ..
      '    D     D    \n' ..
      '   E       E   \n' ..
      '  F         F  \n' ..
      ' G           G \n' ..
      'H             H\n' ..
      ' G           G \n' ..
      '  F         F  \n' ..
      '   E       E   \n' ..
      '    D     D    \n' ..
      '     C   C     \n' ..
      '      B B      \n' ..
      '       A       \n'

    assert.are.equal(expected, diamond('H'))
  end)
end)

return function(seed)
  local start = 'A'
  local max = seed:byte()
  local min = start:byte()
  local diff = max - min
  
  if diff == 0 then
    return 'A\n'
  end
  
  local diamond = seed .. (' '):rep(diff - 1).. ' ' .. (' '):rep(diff - 1) .. seed .. '\n'
  
  for index=max - 1, min + 1, -1 do
    local c = string.char(index)
    local line = (' '):rep(max - index) .. c .. (' '):rep(index - min)
    line = line .. string.rep(' ', index - min - 1) .. c .. string.rep(' ', max - index) .. '\n'
    diamond = line .. diamond .. line
  end
  
  local first_line = (' '):rep(diff) .. start .. (' '):rep(diff) .. '\n'
  diamond = first_line .. diamond .. first_line
  return diamond
end

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JaeHyoLee's solution

to Diamond in the Lua Track