Add proverb exercise

config.json

@@ -386,6 +386,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "bottle-song",
+        "name": "Bottle Song",
+        "uuid": "b6d90e4b-9f17-459b-aff3-2716e49ccb9c",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "diamond",
         "name": "Diamond",
@@ -410,6 +418,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "proverb",
+        "name": "Proverb",
+        "uuid": "c4bb45c9-9c9d-4a56-933b-df7aa2d45945",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "raindrops",
         "name": "Raindrops",
@@ -579,14 +595,6 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 10
-      },
-      {
-        "slug": "bottle-song",
-        "name": "Bottle Song",
-        "uuid": "b6d90e4b-9f17-459b-aff3-2716e49ccb9c",
-        "practices": [],
-        "prerequisites": [],
-        "difficulty": 5
       }
     ],
     "foregone": [

exercises/practice/proverb/.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/proverb/.docs/instructions.append.md

@@ -0,0 +1,15 @@
+# Instructions append
+
+## Input format
+
+Each list of inputs is represented as a null-terminated string, with a newline character at the end of each input.
+
+An example would be `"nail\nshoe\nhorse\nrider\nmessage\nbattle\nkingdom\n"`
+
+## Registers
+
+| Register | Usage        | Type    | Description                                                    |
+| -------- | ------------ | ------- | -------------------------------------------------------------- |
+| `$a0`    | input        | address | null-terminated input string with newline after each input     |
+| `$a1`    | input/output | address | null-terminated output string                                  |
+| `$t0-9`  | temporary    | any     | for temporary storage                                          |

exercises/practice/proverb/.docs/instructions.md

@@ -0,0 +1,19 @@
+# Instructions
+
+For want of a horseshoe nail, a kingdom was lost, or so the saying goes.
+
+Given a list of inputs, generate the relevant proverb.
+For example, given the list `["nail", "shoe", "horse", "rider", "message", "battle", "kingdom"]`, you will output the full text of this proverbial rhyme:
+
+```text
+For want of a nail the shoe was lost.
+For want of a shoe the horse was lost.
+For want of a horse the rider was lost.
+For want of a rider the message was lost.
+For want of a message the battle was lost.
+For want of a battle the kingdom was lost.
+And all for the want of a nail.
+```
+
+Note that the list of inputs may vary; your solution should be able to handle lists of arbitrary length and content.
+No line of the output text should be a static, unchanging string; all should vary according to the input given.

exercises/practice/proverb/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "impl.mips"
+    ],
+    "test": [
+      "runner.mips"
+    ],
+    "example": [
+      ".meta/example.mips"
+    ]
+  },
+  "blurb": "For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/For_Want_of_a_Nail"
+}

exercises/practice/proverb/.meta/example.mips

@@ -0,0 +1,95 @@
+# | Register | Usage        | Type    | Description                                                |
+# | -------- | ------------ | ------- | ---------------------------------------------------------- |
+# | `$a0`    | input        | address | null-terminated input string with newline after each input |
+# | `$a1`    | input/output | address | null-terminated output string                              |
+# | `$a2`    | temporary    | address | null-terminated or newline-terminated source string        |
+# | `$t0`    | temporary    | byte    | character for output                                       |
+# | `$t6`    | temporary    | address | current string                                             |
+# | `$t7`    | temporary    | address | first string                                               |
+# | `$t8`    | temporary    | byte    | '\n' newline                                               |
+# | `$t9`    | temporary    | address | return address                                             |
+
+.globl recite
+
+.data
+
+for_want: .asciiz "For want of a "
+the:      .asciiz " the "
+was_lost: .asciiz " was lost.\n"
+and_all:  .asciiz "And all for the want of a "
+stop:     .asciiz ".\n"
+
+
+.text
+
+recite:
+        move    $t7, $a0                # first string
+        li      $t8, '\n'
+        move    $t9, $ra                # Save return address
+        j       next
+
+write_line:
+        la      $a2, for_want
+        jal     copy_string
+
+        move    $a2, $t6
+        jal     copy_line
+
+        la      $a2, the
+        jal     copy_string
+
+        move    $a2, $a0
+        jal     copy_line
+
+        la      $a2, was_lost
+        jal     copy_string
+
+next:
+        move    $t6, $a0                # current string
+
+scan:
+        lb      $t0, 0($a0)             # read input byte
+        addi    $a0, $a0, 1             # increment input pointer
+        bne     $t0, $t8, scan          # loop until newline
+
+        lb      $t0, 0($a0)             # first byte after newline
+        bnez    $t0, write_line
+
+write_final_line:
+        la      $a2, and_all
+        jal     copy_string
+
+        move    $a2, $t7                # first string
+        jal     copy_line
+
+        la      $a2, stop
+        jal     copy_string
+
+        jr      $t9
+
+
+copy_string:
+                                        # copy string from source $a2 to destination $a1
+        lb      $t0, 0($a2)             # load source byte
+        sb      $t0, 0($a1)             # write byte to destination
+        addi    $a2, $a2, 1             # increment souce pointer
+        addi    $a1, $a1, 1             # increment destination pointer
+        bnez    $t0, copy_string        # repeat until we have reached null terminator
+
+        subi    $a1, $a1, 1             # decrement destination pointer,
+                                        # ready to append other strings
+        jr      $ra
+
+
+copy_line:
+                                        # copy line from source $a2 to destination $a1
+                                        # assume $t8 is '\n'
+        lb      $t0, 0($a2)             # load source byte
+        sb      $t0, 0($a1)             # write byte to destination
+        addi    $a2, $a2, 1             # increment souce pointer
+        addi    $a1, $a1, 1             # increment destination pointer
+        bne     $t0, $t8, copy_line     # repeat until we have reached '\n' line terminator
+
+        subi    $a1, $a1, 1             # decrement destination pointer,
+                                        # ready to append other strings
+        jr      $ra

exercises/practice/proverb/.meta/tests.toml

@@ -0,0 +1,29 @@
+# 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.
+
+[e974b73e-7851-484f-8d6d-92e07fe742fc]
+description = "zero pieces"
+include = false
+
+[2fcd5f5e-8b82-4e74-b51d-df28a5e0faa4]
+description = "one piece"
+
+[d9d0a8a1-d933-46e2-aa94-eecf679f4b0e]
+description = "two pieces"
+
+[c95ef757-5e94-4f0d-a6cb-d2083f5e5a83]
+description = "three pieces"
+
+[433fb91c-35a2-4d41-aeab-4de1e82b2126]
+description = "full proverb"
+
+[c1eefa5a-e8d9-41c7-91d4-99fab6d6b9f7]
+description = "four pieces modernized"

exercises/practice/proverb/impl.mips

@@ -0,0 +1,10 @@
+# | Register | Usage        | Type    | Description                                                |
+# | -------- | ------------ | ------- | ---------------------------------------------------------- |
+# | `$a0`    | input        | address | null-terminated input string with newline after each input |
+# | `$a1`    | input/output | address | null-terminated output string                              |
+# | `$t0-9`  | temporary    | any     | for temporary storage                                      |
+
+.globl recite
+
+recite:
+        jr $ra