Add roman-numerals exercise

config.json

@@ -152,6 +152,15 @@
         "difficulty": 4,
         "topics": []
       },
+      {
+        "slug": "roman-numerals",
+        "name": "Roman Numerals",
+        "uuid": "fa283d1e-2005-40d3-9a30-252d06d98523",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4,
+        "topics": []
+      },
       {
         "slug": "scrabble-score",
         "name": "Scrabble Score",

exercises/practice/roman-numerals/.docs/hints.md

@@ -0,0 +1,6 @@
+# Hints
+
+## General
+
+- The `$t0-9` registers can be used to temporarily store values
+- The instructions specify which registers are used as input and output

exercises/practice/roman-numerals/.docs/instructions.append.md

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+# Instructions append
+
+## Registers
+
+| Register | Usage        | Type    | Description                   |
+| -------- | ------------ | ------- | ----------------------------- |
+| `$a0`    | input        | integer | given number                  |
+| `$a1`    | input/output | address | null-terminated result string |
+| `$t0-9`  | temporary    | any     | for temporary storage         |

exercises/practice/roman-numerals/.docs/instructions.md

@@ -0,0 +1,41 @@
+# Instructions
+
+Write a function to convert from normal numbers to Roman Numerals.
+
+The Romans were a clever bunch.
+They conquered most of Europe and ruled it for hundreds of years.
+They invented concrete and straight roads and even bikinis.
+One thing they never discovered though was the number zero.
+This made writing and dating extensive histories of their exploits slightly more challenging, but the system of numbers they came up with is still in use today.
+For example the BBC uses Roman numerals to date their programs.
+
+The Romans wrote numbers using letters - I, V, X, L, C, D, M.
+(notice these letters have lots of straight lines and are hence easy to hack into stone tablets).
+
+```text
+ 1  => I
+10  => X
+ 7  => VII
+```
+
+The maximum number supported by this notation is 3,999.
+(The Romans themselves didn't tend to go any higher)
+
+Wikipedia says: Modern Roman numerals ... are written by expressing each digit separately starting with the left most digit and skipping any digit with a value of zero.
+
+To see this in practice, consider the example of 1990.
+
+In Roman numerals 1990 is MCMXC:
+
+1000=M
+900=CM
+90=XC
+
+2008 is written as MMVIII:
+
+2000=MM
+8=VIII
+
+Learn more about [Roman numerals on Wikipedia][roman-numerals].
+
+[roman-numerals]: https://wiki.imperivm-romanvm.com/wiki/Roman_Numerals

exercises/practice/roman-numerals/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "impl.mips"
+    ],
+    "test": [
+      "runner.mips"
+    ],
+    "example": [
+      ".meta/example.mips"
+    ]
+  },
+  "blurb": "Write a function to convert from normal numbers to Roman Numerals.",
+  "source": "The Roman Numeral Kata",
+  "source_url": "https://codingdojo.org/kata/RomanNumerals/"
+}

exercises/practice/roman-numerals/.meta/example.mips

@@ -0,0 +1,96 @@
+# Converts number to Roman Numerals.
+#
+# $a0 - input value of integer in question
+# $a1 - input, pointer to expected location of transcribed string
+# $t0 - address of fives
+# $t1 - address of ones
+# $t2 - return address
+# $t3 - low digits of input
+# $t4 - current digit value (0..9)
+# $t5 - current digit place (0 for units, 1 for tens, 2 for hundreds, 3 for thousands)
+# $t6 - divisor
+# $t7 - character for roman numeral, in {I, V, X, L, C, D, M}
+
+.globl roman
+
+.data
+
+ones: .asciiz  "IXCM"
+fives: .asciiz  "VLD"
+
+.text
+
+roman:
+        move    $t2, $ra                # make a copy of return address
+        la      $t1, ones               # address of ones
+        la      $t0, fives              # address of fives
+
+        li      $t6, 1000
+        div     $a0, $t6
+        mfhi    $t3                     # input % 1000
+        mflo    $t4                     # thousands digit
+        li      $t5, 3                  # thousands place
+        jal     convert_digit
+
+        li      $t6, 100
+        div     $t3, $t6
+        mfhi    $t3                     # input % 100
+        mflo    $t4                     # hundreds digit
+        li      $t5, 2                  # hundreds place
+        jal     convert_digit
+
+        li      $t6, 10
+        div     $t3, $t6
+        mfhi    $t3                     # input % 10
+        mflo    $t4                     # tens digit
+        li      $t5, 1                  # tens place
+        jal     convert_digit
+
+        move    $t4, $t3                # units digit
+        li      $t5, 0                  # units place
+        jal     convert_digit
+
+        sb      $zero, 0($a1)           # write '\0' terminator
+
+        jr      $t2                     # return to caller
+
+convert_digit:
+                                        # subroutine that converts current digit
+                                        # (with value $t4, place $t5) to roman numerals.
+        li      $t6, 5
+        rem     $t6, $t4, $t6
+        bne     $t6, 4, simple          # jump forward if the digit is not 4 (mod 5)
+
+        add     $t7, $t1, $t5           # address of character for digit 1
+        lb      $t7, 0($t7)             # read character for digit 1
+        sb      $t7, 0($a1)             # write character for digit 1
+        addi    $a1, $a1, 1             # increment output address
+
+        addi    $t4, $t4, 1             # increment digit by 1
+        bne     $t4, 10, simple         # jump forward if the digit has not become 10
+
+        li      $t4, 1                  # replace 10 with digit 1
+        addi    $t5, $t5, 1             # with increased place value
+
+simple:
+        blt     $t4, 5, while_ones      # jump forward if the digit is below 5
+
+        add     $t7, $t0, $t5           # address of character for digit 5
+        lb      $t7, 0($t7)             # read character for digit 5
+        sb      $t7, 0($a1)             # write character for digit 5
+        addi    $a1, $a1, 1             # increment output address
+
+        subi    $t4, $t4, 5             # decrease digit by 5
+        j       while_ones              # check if we need to write digit 1
+
+do_ones:
+        add     $t7, $t1, $t5           # address of character for digit 1
+        lb      $t7, 0($t7)             # read character for digit 1
+        sb      $t7, 0($a1)             # write character for digit 1
+        addi    $a1, $a1, 1             # increment output address
+
+        subi    $t4, $t4, 1             # decrease digit by 1
+
+while_ones:
+        bne     $t4, $zero, do_ones     # loop until digit is 0
+        jr      $ra                     # return to caller (roman)

exercises/practice/roman-numerals/.meta/tests.toml

@@ -0,0 +1,88 @@
+# 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.
+
+[19828a3a-fbf7-4661-8ddd-cbaeee0e2178]
+description = "1 is I"
+
+[f088f064-2d35-4476-9a41-f576da3f7b03]
+description = "2 is II"
+
+[b374a79c-3bea-43e6-8db8-1286f79c7106]
+description = "3 is III"
+
+[05a0a1d4-a140-4db1-82e8-fcc21fdb49bb]
+description = "4 is IV"
+
+[57c0f9ad-5024-46ab-975d-de18c430b290]
+description = "5 is V"
+
+[20a2b47f-e57f-4797-a541-0b3825d7f249]
+description = "6 is VI"
+
+[ff3fb08c-4917-4aab-9f4e-d663491d083d]
+description = "9 is IX"
+
+[6d1d82d5-bf3e-48af-9139-87d7165ed509]
+description = "16 is XVI"
+
+[2bda64ca-7d28-4c56-b08d-16ce65716cf6]
+description = "27 is XXVII"
+
+[a1f812ef-84da-4e02-b4f0-89c907d0962c]
+description = "48 is XLVIII"
+
+[607ead62-23d6-4c11-a396-ef821e2e5f75]
+description = "49 is XLIX"
+
+[d5b283d4-455d-4e68-aacf-add6c4b51915]
+description = "59 is LIX"
+
+[4465ffd5-34dc-44f3-ada5-56f5007b6dad]
+description = "66 is LXVI"
+
+[46b46e5b-24da-4180-bfe2-2ef30b39d0d0]
+description = "93 is XCIII"
+
+[30494be1-9afb-4f84-9d71-db9df18b55e3]
+description = "141 is CXLI"
+
+[267f0207-3c55-459a-b81d-67cec7a46ed9]
+description = "163 is CLXIII"
+
+[902ad132-0b4d-40e3-8597-ba5ed611dd8d]
+description = "166 is CLXVI"
+
+[cdb06885-4485-4d71-8bfb-c9d0f496b404]
+description = "402 is CDII"
+
+[6b71841d-13b2-46b4-ba97-dec28133ea80]
+description = "575 is DLXXV"
+
+[dacb84b9-ea1c-4a61-acbb-ce6b36674906]
+description = "666 is DCLXVI"
+
+[432de891-7fd6-4748-a7f6-156082eeca2f]
+description = "911 is CMXI"
+
+[e6de6d24-f668-41c0-88d7-889c0254d173]
+description = "1024 is MXXIV"
+
+[efbe1d6a-9f98-4eb5-82bc-72753e3ac328]
+description = "1666 is MDCLXVI"
+
+[bb550038-d4eb-4be2-a9ce-f21961ac3bc6]
+description = "3000 is MMM"
+
+[3bc4b41c-c2e6-49d9-9142-420691504336]
+description = "3001 is MMMI"
+
+[4e18e96b-5fbb-43df-a91b-9cb511fe0856]
+description = "3999 is MMMCMXCIX"

exercises/practice/roman-numerals/impl.mips

@@ -0,0 +1,10 @@
+# | Register | Usage        | Type    | Description                   |
+# | -------- | ------------ | ------- | ----------------------------- |
+# | `$a0`    | input        | integer | given number                  |
+# | `$a1`    | input/output | address | null-terminated result string |
+# | `$t0-9`  | temporary    | any     | for temporary storage         |
+
+.globl roman
+
+roman:
+        jr $ra