Add armstrong-numbers exercise

config.json

@@ -74,6 +74,14 @@
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "armstrong-numbers",
+        "name": "Armstrong Numbers",
+        "uuid": "556a01ac-2d5b-4cbb-a5a5-c5a9d869c4cd",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "bob",
         "name": "Bob",

exercises/practice/armstrong-numbers/.docs/instructions.md

@@ -0,0 +1,14 @@
+# Instructions
+
+An [Armstrong number][armstrong-number] is a number that is the sum of its own digits each raised to the power of the number of digits.
+
+For example:
+
+- 9 is an Armstrong number, because `9 = 9^1 = 9`
+- 10 is _not_ an Armstrong number, because `10 != 1^2 + 0^2 = 1`
+- 153 is an Armstrong number, because: `153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153`
+- 154 is _not_ an Armstrong number, because: `154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190`
+
+Write some code to determine whether a number is an Armstrong number.
+
+[armstrong-number]: https://en.wikipedia.org/wiki/Narcissistic_number

exercises/practice/armstrong-numbers/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "armstrong_numbers.s"
+    ],
+    "test": [
+      "armstrong_numbers_test.c"
+    ],
+    "example": [
+      ".meta/example.s"
+    ]
+  },
+  "blurb": "Determine if a number is an Armstrong number.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Narcissistic_number"
+}

exercises/practice/armstrong-numbers/.meta/example.s

@@ -0,0 +1,39 @@
+.text
+.globl is_armstrong_number
+
+/* extern int is_armstrong_number(unsigned number); */
+is_armstrong_number:
+        mov     x1, #10
+        mov     x4, x0                  /* number */
+        mov     x5, xzr                 /* digit count */
+        mov     x6, xzr                 /* sum of digit powers */
+
+.count_digit:
+        add     x5, x5, #1
+        udiv    x0, x0, x1              /* quotient */
+        cbnz    x0, .count_digit
+
+        mov     x0, x4                  /* number */
+
+.extract_digit:
+        udiv    x2, x0, x1              /* quotient */
+        msub    x3, x2, x1, x0          /* remainder becomes base */
+        mov     x0, x2
+        mov     x9, #1                  /* multiplier */
+        mov     x10, x5                 /* exponent */
+
+.raise:
+        mul     x7, x9, x3
+        tst     x10, #1
+        csel    x9, x7, x9, ne          /* multiplier *= base, provided exponent is odd */
+
+        mul     x3, x3, x3              /* square base */
+        lsr     x10, x10, #1            /* halve exponent */
+        cbnz    x10, .raise
+
+        add     x6, x6, x9              /* update sum of digit powers */
+        cbnz    x2, .extract_digit
+
+        cmp     x6, x4
+        cset    x0, eq                  /* 1 if sum of digit powers == number, otherwise 0 */
+        ret

exercises/practice/armstrong-numbers/.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.
+
+[c1ed103c-258d-45b2-be73-d8c6d9580c7b]
+description = "Zero is an Armstrong number"
+
+[579e8f03-9659-4b85-a1a2-d64350f6b17a]
+description = "Single-digit numbers are Armstrong numbers"
+
+[2d6db9dc-5bf8-4976-a90b-b2c2b9feba60]
+description = "There are no two-digit Armstrong numbers"
+
+[509c087f-e327-4113-a7d2-26a4e9d18283]
+description = "Three-digit number that is an Armstrong number"
+
+[7154547d-c2ce-468d-b214-4cb953b870cf]
+description = "Three-digit number that is not an Armstrong number"
+
+[6bac5b7b-42e9-4ecb-a8b0-4832229aa103]
+description = "Four-digit number that is an Armstrong number"
+
+[eed4b331-af80-45b5-a80b-19c9ea444b2e]
+description = "Four-digit number that is not an Armstrong number"
+
+[f971ced7-8d68-4758-aea1-d4194900b864]
+description = "Seven-digit number that is an Armstrong number"
+
+[7ee45d52-5d35-4fbd-b6f1-5c8cd8a67f18]
+description = "Seven-digit number that is not an Armstrong number"
+
+[5ee2fdf8-334e-4a46-bb8d-e5c19c02c148]
+description = "Armstrong number containing seven zeroes"
+include = false
+
+[12ffbf10-307a-434e-b4ad-c925680e1dd4]
+description = "The largest and last Armstrong number"
+include = false

exercises/practice/armstrong-numbers/Makefile

@@ -0,0 +1,36 @@
+AS = aarch64-linux-gnu-as
+CC = aarch64-linux-gnu-gcc
+
+CFLAGS = -g -Wall -Wextra -pedantic -Werror
+LDFLAGS =
+
+ALL_LDFLAGS = -pie -Wl,--fatal-warnings
+
+ALL_CFLAGS = -std=c99 -fPIE $(CFLAGS)
+ALL_LDFLAGS += $(LDFLAGS)
+
+C_OBJS = $(patsubst %.c,%.o,$(wildcard *.c))
+AS_OBJS = $(patsubst %.s,%.o,$(wildcard *.s))
+ALL_OBJS = $(filter-out example.o,$(C_OBJS) $(AS_OBJS) vendor/unity.o)
+
+CC_CMD = $(CC) $(ALL_CFLAGS) -c -o $@ $<
+
+all: tests
+	qemu-aarch64 -L /usr/aarch64-linux-gnu ./$<
+
+tests: $(ALL_OBJS)
+	@$(CC) $(ALL_CFLAGS) $(ALL_LDFLAGS) -o $@ $(ALL_OBJS)
+
+%.o: %.s
+	@$(AS) -o $@ $<
+
+%.o: %.c
+	@$(CC_CMD)
+
+vendor/unity.o: vendor/unity.c vendor/unity.h vendor/unity_internals.h
+	@$(CC_CMD)
+
+clean:
+	@rm -f *.o vendor/*.o tests
+
+.PHONY: all clean

exercises/practice/armstrong-numbers/armstrong_numbers.s

@@ -0,0 +1,5 @@
+.text
+.globl is_armstrong_number
+
+is_armstrong_number:
+    ret

exercises/practice/armstrong-numbers/armstrong_numbers_test.c

@@ -0,0 +1,67 @@
+#include "vendor/unity.h"
+
+extern int is_armstrong_number(unsigned number);
+
+void setUp(void) {
+}
+
+void tearDown(void) {
+}
+
+void test_zero_is_an_armstrong_number(void) {
+    TEST_ASSERT_TRUE(is_armstrong_number(0));
+}
+
+void test_singledigit_numbers_are_armstrong_numbers(void) {
+    TEST_IGNORE();
+    TEST_ASSERT_TRUE(is_armstrong_number(5));
+}
+
+void test_there_are_no_twodigit_armstrong_numbers(void) {
+    TEST_IGNORE();
+    TEST_ASSERT_FALSE(is_armstrong_number(10));
+}
+
+void test_threedigit_number_that_is_an_armstrong_number(void) {
+    TEST_IGNORE();
+    TEST_ASSERT_TRUE(is_armstrong_number(153));
+}
+
+void test_threedigit_number_that_is_not_an_armstrong_number(void) {
+    TEST_IGNORE();
+    TEST_ASSERT_FALSE(is_armstrong_number(100));
+}
+
+void test_fourdigit_number_that_is_an_armstrong_number(void) {
+    TEST_IGNORE();
+    TEST_ASSERT_TRUE(is_armstrong_number(9474));
+}
+
+void test_fourdigit_number_that_is_not_an_armstrong_number(void) {
+    TEST_IGNORE();
+    TEST_ASSERT_FALSE(is_armstrong_number(9475));
+}
+
+void test_sevendigit_number_that_is_an_armstrong_number(void) {
+    TEST_IGNORE();
+    TEST_ASSERT_TRUE(is_armstrong_number(9926315));
+}
+
+void test_sevendigit_number_that_is_not_an_armstrong_number(void) {
+    TEST_IGNORE();
+    TEST_ASSERT_FALSE(is_armstrong_number(9926314));
+}
+
+int main(void) {
+    UNITY_BEGIN();
+    RUN_TEST(test_zero_is_an_armstrong_number);
+    RUN_TEST(test_singledigit_numbers_are_armstrong_numbers);
+    RUN_TEST(test_there_are_no_twodigit_armstrong_numbers);
+    RUN_TEST(test_threedigit_number_that_is_an_armstrong_number);
+    RUN_TEST(test_threedigit_number_that_is_not_an_armstrong_number);
+    RUN_TEST(test_fourdigit_number_that_is_an_armstrong_number);
+    RUN_TEST(test_fourdigit_number_that_is_not_an_armstrong_number);
+    RUN_TEST(test_sevendigit_number_that_is_an_armstrong_number);
+    RUN_TEST(test_sevendigit_number_that_is_not_an_armstrong_number);
+    return UNITY_END();
+}