Add prism

config.json

@@ -902,6 +902,14 @@
           "math"
         ]
       },
+      {
+        "slug": "prism",
+        "name": "Prism",
+        "uuid": "bd71935a-a63a-4be3-b0ec-982240515b59",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
+      },
       {
         "slug": "robot-name",
         "name": "Robot Name",

exercises/practice/prism/.busted

@@ -0,0 +1,5 @@
+return {
+  default = {
+    ROOT = { '.' }
+  }
+}

exercises/practice/prism/.docs/instructions.md

@@ -0,0 +1,36 @@
+# Instructions
+
+Before activating the laser array, you must predict the exact order in which crystals will be hit, identified by their sample IDs.
+
+## Example Test Case
+
+Consider this crystal array configuration:
+
+```json
+{
+  "start": { "x": 0, "y": 0, "angle": 0 },
+  "prisms": [
+    { "id": 3, "x": 30, "y": 10, "angle": 45 },
+    { "id": 1, "x": 10, "y": 10, "angle": -90 },
+    { "id": 2, "x": 10, "y": 0, "angle": 90 },
+    { "id": 4, "x": 20, "y": 0, "angle": 0 }
+  ]
+}
+```
+
+## What's Happening
+
+The laser starts at the origin `(0, 0)` and fires horizontally to the right at angle 0°.
+Here's the step-by-step beam path:
+
+**Step 1**: The beam travels along the x-axis (y = 0) and first encounters **Crystal #2** at position `(10, 0)`.
+This crystal has a refraction angle of 90°, which means it bends the beam perpendicular to its current path.
+The beam, originally traveling at 0°, is now redirected to 90° (straight up).
+
+**Step 2**: The beam now travels vertically upward from position `(10, 0)` and strikes **Crystal #1** at position `(10, 10)`.
+This crystal has a refraction angle of -90°, bending the beam by -90° relative to its current direction.
+The beam was traveling at 90°, so after refraction it's now at 0° (90° + (-90°) = 0°), traveling horizontally to the right again.
+
+**Step 3**: From position `(10, 10)`, the beam travels horizontally and encounters **Crystal #3** at position `(30, 10)`.
+This crystal refracts the beam by 45°, changing its direction to 45°.
+The beam continues into empty space beyond the array.

exercises/practice/prism/.docs/introduction.md

@@ -0,0 +1,5 @@
+# Introduction
+
+You're a researcher at **PRISM** (Precariously Redirected Illumination Safety Management), working with a precision laser calibration system that tests experimental crystal prisms.
+These crystals are being developed for next-generation optical computers, and each one has unique refractive properties based on its molecular structure.
+The lab's laser system can damage crystals if they receive unexpected illumination, so precise path prediction is critical.

exercises/practice/prism/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "BNAndras"
+  ],
+  "files": {
+    "solution": [
+      "prism.lua"
+    ],
+    "test": [
+      "prism_spec.lua"
+    ],
+    "example": [
+      ".meta/example.lua"
+    ]
+  },
+  "blurb": "Calculate the path of a laser through reflective prisms.",
+  "source": "FraSanga",
+  "source_url": "https://github.com/exercism/problem-specifications/pull/2625"
+}

exercises/practice/prism/.meta/example.lua

@@ -0,0 +1,45 @@
+local function find_sequence(start, prisms)
+  local x, y, angle = start.x, start.y, start.angle
+  local sequence = {}
+
+  while true do
+    local rad = angle * math.pi / 180
+    local dirX = math.cos(rad)
+    local dirY = math.sin(rad)
+
+    local nearest = nil
+    local nearestDist = math.huge
+
+    for _, prism in ipairs(prisms) do
+      local dx = prism.x - x
+      local dy = prism.y - y
+
+      local dist = dx * dirX + dy * dirY
+      -- ignore prisms behind or at the start
+      if dist > 1e-6 then
+        local crossSq = (dx - dist * dirX) ^ 2 + (dy - dist * dirY) ^ 2
+
+        -- Bail if outside relative tolerance (more wiggle room for further prisms)
+        if crossSq < 1e-6 * math.max(1, dist * dist) then
+          if dist < nearestDist then
+            nearestDist = dist
+            nearest = prism
+          end
+        end
+      end
+    end
+
+    if not nearest then
+      break
+    end
+
+    table.insert(sequence, nearest.id)
+    x = nearest.x
+    y = nearest.y
+    angle = (angle + nearest.angle) % 360
+  end
+
+  return sequence
+end
+
+return { find_sequence = find_sequence }

exercises/practice/prism/.meta/spec_generator.lua

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+return {
+  module_name = 'prism',
+
+  generate_test = function(case)
+    local lines = {}
+
+    local function snake_case(str)
+      local s = str:gsub('%u', function(c)
+        return '_' .. c:lower()
+      end)
+      if s:sub(1, 1) == '_' then
+        s = s:sub(2)
+      end
+      return s
+    end
+
+    table.insert(lines,
+                 string.format("local start = { x = %s, y = %s, angle = %s }", case.input.start.x, case.input.start.y,
+                               case.input.start.angle))
+
+    if #case.input.prisms == 0 then
+      table.insert(lines, "local prisms = {}")
+    else
+      table.insert(lines, "local prisms = {")
+      for _, prism in ipairs(case.input.prisms) do
+        table.insert(lines, string.format("  { id = %s, x = %s, y = %s, angle = %s },", prism.id, prism.x, prism.y,
+                                          prism.angle))
+      end
+      table.insert(lines, "}")
+    end
+
+    local expected = ""
+    if #case.expected.sequence == 0 then
+      expected = "{}"
+    else
+      expected = string.format("{ %s }", table.concat(case.expected.sequence, ", "))
+    end
+
+    table.insert(lines, string.format("local expected = %s", expected))
+    table.insert(lines, string.format("local result = prism.%s(start, prisms)", snake_case(case.property)))
+    table.insert(lines, "assert.are.same(expected, result)")
+
+    return table.concat(lines, "\n")
+  end
+}

exercises/practice/prism/.meta/tests.toml

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+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[ec65d3b3-f7bf-4015-8156-0609c141c4c4]
+description = "zero prisms"
+
+[ec0ca17c-0c5f-44fb-89ba-b76395bdaf1c]
+description = "one prism one hit"
+
+[0db955f2-0a27-4c82-ba67-197bd6202069]
+description = "one prism zero hits"
+
+[8d92485b-ebc0-4ee9-9b88-cdddb16b52da]
+description = "going up zero hits"
+
+[78295b3c-7438-492d-8010-9c63f5c223d7]
+description = "going down zero hits"
+
+[acc723ea-597b-4a50-8d1b-b980fe867d4c]
+description = "going left zero hits"
+
+[3f19b9df-9eaa-4f18-a2db-76132f466d17]
+description = "negative angle"
+
+[96dacffb-d821-4cdf-aed8-f152ce063195]
+description = "large angle"
+
+[513a7caa-957f-4c5d-9820-076842de113c]
+description = "upward refraction two hits"
+
+[d452b7c7-9761-4ea9-81a9-2de1d73eb9ef]
+description = "downward refraction two hits"
+
+[be1a2167-bf4c-4834-acc9-e4d68e1a0203]
+description = "same prism twice"
+
+[df5a60dd-7c7d-4937-ac4f-c832dae79e2e]
+description = "simple path"
+
+[8d9a3cc8-e846-4a3b-a137-4bfc4aa70bd1]
+description = "multiple prisms floating point precision"
+
+[e077fc91-4e4a-46b3-a0f5-0ba00321da56]
+description = "complex path with multiple prisms floating point precision"

exercises/practice/prism/prism.lua

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+local function find_sequence(start, prisms)
+
+end
+
+return { find_sequence = find_sequence }