feat: Add Grains (resolves #149) (#167)

config.json

@@ -86,6 +86,14 @@
         "difficulty": 3,
         "topics": []
       },
+      {
+        "slug": "grains",
+        "name": "Grains",
+        "uuid": "0a05186b-c395-40dc-b690-b1364978d7d3",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
+      },
       {
         "slug": "triangle",
         "name": "Triangle",

exercises/practice/grains/.docs/instructions.md

@@ -0,0 +1,15 @@
+# Instructions
+
+Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
+
+There once was a wise servant who saved the life of a prince.
+The king promised to pay whatever the servant could dream up.
+Knowing that the king loved chess, the servant told the king he would like to have grains of wheat.
+One grain on the first square of a chess board, with the number of grains doubling on each successive square.
+
+There are 64 squares on a chessboard (where square 1 has one grain, square 2 has two grains, and so on).
+
+Write code that shows:
+
+- how many grains were on a given square, and
+- the total number of grains on the chessboard

exercises/practice/grains/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "impl.mips"
+    ],
+    "test": [
+      "runner.mips"
+    ],
+    "example": [
+      ".meta/example.mips"
+    ]
+  },
+  "blurb": "Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.",
+  "source": "The CodeRanch Cattle Drive, Assignment 6",
+  "source_url": "https://coderanch.com/wiki/718824/Grains"
+}

exercises/practice/grains/.meta/example.mips

@@ -0,0 +1,32 @@
+# Convert square to number of grains
+#
+# Strategy: shift 1 left by (the square number minus 1)
+#
+# $a0 - input, square number in the range 1..64
+# $v0 - low 32 bits of output
+# $v1 - high 32 bits of output
+
+.globl square
+
+square:
+    move $v0, $zero
+    move $v1, $zero
+    li $t0, 1
+    blt $a0, $t0, invalid_square
+    sub $a0, $a0, $t0
+    li $t1, 32
+    blt $a0, $t1, low
+    sub $a0, $a0, $t1
+    blt $a0, $t1, high
+
+invalid_square:
+    jr $ra
+
+low:
+    sllv $v0, $t0, $a0
+    jr $ra
+
+high:
+    sllv $v1, $t0, $a0
+    jr $ra
+

exercises/practice/grains/.meta/tests.toml

@@ -0,0 +1,45 @@
+# 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.
+
+[9fbde8de-36b2-49de-baf2-cd42d6f28405]
+description = "returns the number of grains on the square -> grains on square 1"
+
+[ee1f30c2-01d8-4298-b25d-c677331b5e6d]
+description = "returns the number of grains on the square -> grains on square 2"
+
+[10f45584-2fc3-4875-8ec6-666065d1163b]
+description = "returns the number of grains on the square -> grains on square 3"
+
+[a7cbe01b-36f4-4601-b053-c5f6ae055170]
+description = "returns the number of grains on the square -> grains on square 4"
+
+[c50acc89-8535-44e4-918f-b848ad2817d4]
+description = "returns the number of grains on the square -> grains on square 16"
+
+[acd81b46-c2ad-4951-b848-80d15ed5a04f]
+description = "returns the number of grains on the square -> grains on square 32"
+
+[c73b470a-5efb-4d53-9ac6-c5f6487f227b]
+description = "returns the number of grains on the square -> grains on square 64"
+
+[1d47d832-3e85-4974-9466-5bd35af484e3]
+description = "returns the number of grains on the square -> square 0 raises an exception"
+
+[61974483-eeb2-465e-be54-ca5dde366453]
+description = "returns the number of grains on the square -> negative square raises an exception"
+
+[a95e4374-f32c-45a7-a10d-ffec475c012f]
+description = "returns the number of grains on the square -> square greater than 64 raises an exception"
+
+[6eb07385-3659-4b45-a6be-9dc474222750]
+description = "returns the total number of grains on the board"
+include = false
+

exercises/practice/grains/runner.mips

@@ -0,0 +1,115 @@
+#
+# Test square with some examples
+#
+# s0 - num of tests left to run
+# s1 - address of input word
+# s2 - address of expected low output word
+# s3 - address of expected high output word
+# s4 - input word
+# s5 - low output word
+# s6 - high output word
+#
+# square must:
+# - be named square and declared as global
+# - read input integer from a0
+# - follow the convention of using the t0-9 registers for temporary storage
+# - (if it wants to use s0-7 then it is responsible for pushing existing values to the stack then popping them back off before returning)
+# - write low word of integer result to v0
+# - write high word of integer result to v1
+
+.data
+
+n: .word 10  # number of test cases
+ins: .word 1, 2, 3, 4, 16, 32, 64, 0, -1, 65  # input numbers
+lows: .word 1, 2, 4, 8, 32768, 2147483648, 0, 0, 0, 0  # expected result (low word)
+highs: .word 0, 0, 0, 0, 0, 0, 2147483648, 0, 0, 0  # expected result (high word)
+
+failmsg: .asciiz "failed for test input: "
+expectedmsg: .asciiz ". expected "
+commamsg: .asciiz ", "
+tobemsg: .asciiz " to be "
+okmsg: .asciiz "all tests passed"
+
+
+.text
+
+runner:
+        lw      $s0, n
+        la      $s1, ins
+        la      $s2, lows
+        la      $s3, highs
+
+run_test:
+        lw      $s4, 0($s1)             # read input from memory
+        move    $a0, $s4                # move it to a0
+        jal     square                  # call subroutine under test
+        move    $s5, $v0                # move return value in v0 to s5 because we need v0 for syscall
+        move    $s6, $v1                # move return value in v1 to s6
+
+        lw      $t0, 0($s2)             # read expected low output from memory
+        bne     $t0, $s5, exit_fail     # if expected doesn't match actual, jump to fail
+        lw      $t1, 0($s3)             # read expected high output from memory
+        bne     $t1, $s6, exit_fail     # if expected doesn't match actual, jump to fail
+
+        addi    $s1, $s1, 4             # move to next word in input
+        addi    $s2, $s2, 4             # move to next low word in output
+        addi    $s3, $s3, 4             # move to next high word in output
+        sub     $s0, $s0, 1             # decrement num of tests left to run
+        bgt     $s0, $zero, run_test    # if more than zero tests to run, jump to run_test
+
+exit_ok:
+        la      $a0, okmsg              # put address of okmsg into a0
+        li      $v0, 4                  # 4 is print string
+        syscall
+
+        li      $v0, 10                 # 10 is exit with zero status (clean exit)
+        syscall
+
+exit_fail:
+        la      $a0, failmsg            # put address of failmsg into a0
+        li      $v0, 4                  # 4 is print string
+        syscall
+
+        move    $a0, $s4                # set arg of syscall to input that failed the test
+        li      $v0, 1                  # 1 is print int
+        syscall
+
+        la      $a0, expectedmsg
+        li      $v0, 4
+        syscall
+
+        move    $a0, $s5                # print actual low that failed on
+        li      $v0, 1
+        syscall
+
+        la      $a0, commamsg
+        li      $v0, 4
+        syscall
+
+        move    $a0, $s6                # print actual high that failed on
+        li      $v0, 1
+        syscall
+
+        la      $a0, tobemsg
+        li      $v0, 4
+        syscall
+
+        lw      $a0, 0($s2)             # print expected low value that failed on
+        li      $v0, 1
+        syscall
+
+        la      $a0, commamsg
+        li      $v0, 4
+        syscall
+
+        lw      $a0, 0($s3)             # print expected high value that failed on
+        li      $v0, 1
+        syscall
+
+        li      $a0, 1                  # set exit code to 1
+        li      $v0, 17                 # terminate with the exit code in $a0
+        syscall
+
+# # Include your implementation here if you wish to run this from the MARS GUI.
+# .include "impl.mips"
+