Add resistor-color-trio exercise (#125)

We also modify the resistor-color-duo exercise so
that colors are passed as an array of strings.

config.json

@@ -186,6 +186,14 @@
         "prerequisites": [],
         "difficulty": 3
       },
+      {
+        "slug": "resistor-color-trio",
+        "name": "Resistor Color Trio",
+        "uuid": "bae67e03-a8ce-4774-8dcf-342251eb4de9",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "scrabble-score",
         "name": "Scrabble Score",

exercises/practice/resistor-color-duo/.meta/example.s

@@ -27,9 +27,9 @@ color_array:
 .globl value
 
 color_code:
-        adrp    x7, color_array
-        add     x7, x7, :lo12:color_array
-        mov     x2, x7
+        adrp    x1, color_array
+        add     x1, x1, :lo12:color_array
+        mov     x2, x1
 
 .next:
         mov     x3, x0
@@ -44,18 +44,20 @@ color_code:
         cbnz    w5, .compare
 
         sub     x2, x2, #8
-        sub     x0, x2, x7
+        sub     x0, x2, x1
         lsr     x0, x0, #3
         ret
 
-/* extern int value(const char *first, const char *second, const char *third); */
+/* extern int value(const char **colors); */
 value:
-        mov     x9, lr
+        mov     x8, x0
+        mov     x9, lr                 /* preserve return address */
+        mov     x10, #10
+        ldr     x0, [x8], #8           /* load address of first color */
         bl      color_code
         mov     x11, x0
-        mov     x0, x1
+        ldr     x0, [x8]               /* load address of second color */
         bl      color_code
-        mov     x10, #10
         madd    x0, x10, x11, x0
         mov     lr, x9
         ret

exercises/practice/resistor-color-duo/resistor_color_duo_test.c

@@ -2,7 +2,7 @@
 
 #include <stddef.h>
 
-extern int value(const char *first, const char *second, const char *third);
+extern int value(const char **colors);
 
 void setUp(void) {
 }
@@ -11,37 +11,73 @@ void tearDown(void) {
 }
 
 void test_brown_and_black(void) {
-    TEST_ASSERT_EQUAL_INT(10, value("brown", "black", NULL));
+    const char *colors[] = {
+      "brown",
+      "black",
+      NULL
+    };
+    TEST_ASSERT_EQUAL_INT(10, value(colors));
 }
 
 void test_blue_and_grey(void) {
     TEST_IGNORE();
-    TEST_ASSERT_EQUAL_INT(68, value("blue", "grey", NULL));
+    const char *colors[] = {
+      "blue",
+      "grey",
+      NULL
+    };
+    TEST_ASSERT_EQUAL_INT(68, value(colors));
 }
 
 void test_yellow_and_violet(void) {
     TEST_IGNORE();
-    TEST_ASSERT_EQUAL_INT(47, value("yellow", "violet", NULL));
+    const char *colors[] = {
+      "yellow",
+      "violet",
+      NULL
+    };
+    TEST_ASSERT_EQUAL_INT(47, value(colors));
 }
 
 void test_white_and_red(void) {
     TEST_IGNORE();
-    TEST_ASSERT_EQUAL_INT(92, value("white", "red", NULL));
+    const char *colors[] = {
+      "white",
+      "red",
+      NULL
+    };
+    TEST_ASSERT_EQUAL_INT(92, value(colors));
 }
 
 void test_orange_and_orange(void) {
     TEST_IGNORE();
-    TEST_ASSERT_EQUAL_INT(33, value("orange", "orange", NULL));
+    const char *colors[] = {
+      "orange",
+      "orange",
+      NULL
+    };
+    TEST_ASSERT_EQUAL_INT(33, value(colors));
 }
 
 void test_ignore_additional_colors(void) {
     TEST_IGNORE();
-    TEST_ASSERT_EQUAL_INT(51, value("green", "brown", "orange"));
+    const char *colors[] = {
+      "green",
+      "brown",
+      "orange",
+      NULL
+    };
+    TEST_ASSERT_EQUAL_INT(51, value(colors));
 }
 
 void test_black_and_brown_onedigit(void) {
     TEST_IGNORE();
-    TEST_ASSERT_EQUAL_INT(1, value("black", "brown", NULL));
+    const char *colors[] = {
+      "black",
+      "brown",
+      NULL
+    };
+    TEST_ASSERT_EQUAL_INT(1, value(colors));
 }
 
 int main(void) {

exercises/practice/resistor-color-trio/.docs/instructions.md

@@ -0,0 +1,56 @@
+# Instructions
+
+If you want to build something using a Raspberry Pi, you'll probably use _resistors_.
+For this exercise, you need to know only three things about them:
+
+- Each resistor has a resistance value.
+- Resistors are small - so small in fact that if you printed the resistance value on them, it would be hard to read.
+  To get around this problem, manufacturers print color-coded bands onto the resistors to denote their resistance values.
+- Each band acts as a digit of a number.
+  For example, if they printed a brown band (value 1) followed by a green band (value 5), it would translate to the number 15.
+  In this exercise, you are going to create a helpful program so that you don't have to remember the values of the bands.
+  The program will take 3 colors as input, and outputs the correct value, in ohms.
+  The color bands are encoded as follows:
+
+- black: 0
+- brown: 1
+- red: 2
+- orange: 3
+- yellow: 4
+- green: 5
+- blue: 6
+- violet: 7
+- grey: 8
+- white: 9
+
+In Resistor Color Duo you decoded the first two colors.
+For instance: orange-orange got the main value `33`.
+The third color stands for how many zeros need to be added to the main value.
+The main value plus the zeros gives us a value in ohms.
+For the exercise it doesn't matter what ohms really are.
+For example:
+
+- orange-orange-black would be 33 and no zeros, which becomes 33 ohms.
+- orange-orange-red would be 33 and 2 zeros, which becomes 3300 ohms.
+- orange-orange-orange would be 33 and 3 zeros, which becomes 33000 ohms.
+
+(If Math is your thing, you may want to think of the zeros as exponents of 10.
+If Math is not your thing, go with the zeros.
+It really is the same thing, just in plain English instead of Math lingo.)
+
+This exercise is about translating the colors into a label:
+
+> "... ohms"
+
+So an input of `"orange", "orange", "black"` should return:
+
+> "33 ohms"
+
+When we get to larger resistors, a [metric prefix][metric-prefix] is used to indicate a larger magnitude of ohms, such as "kiloohms".
+That is similar to saying "2 kilometers" instead of "2000 meters", or "2 kilograms" for "2000 grams".
+
+For example, an input of `"orange", "orange", "orange"` should return:
+
+> "33 kiloohms"
+
+[metric-prefix]: https://en.wikipedia.org/wiki/Metric_prefix

exercises/practice/resistor-color-trio/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "resistor_color_trio.s"
+    ],
+    "test": [
+      "resistor_color_trio_test.c"
+    ],
+    "example": [
+      ".meta/example.s"
+    ]
+  },
+  "blurb": "Convert color codes, as used on resistors, to a human-readable label.",
+  "source": "Maud de Vries, Erik Schierboom",
+  "source_url": "https://github.com/exercism/problem-specifications/issues/1549"
+}

exercises/practice/resistor-color-trio/.meta/example.s

@@ -0,0 +1,124 @@
+.data
+black:  .string "black"
+brown:  .string "brown"
+red:    .string "red"
+orange: .string "orange"
+yellow: .string "yellow"
+green:  .string "green"
+blue:   .string "blue"
+violet: .string "violet"
+grey:   .string "grey"
+white:  .string "white"
+
+ohms:   .string " ohms"
+kiloohms:
+        .string " kiloohms"
+megaohms:
+        .string " megaohms"
+gigaohms:
+        .string " gigaohms"
+
+color_array:
+        .dword black
+        .dword brown
+        .dword red
+        .dword orange
+        .dword yellow
+        .dword green
+        .dword blue
+        .dword violet
+        .dword grey
+        .dword white
+        .dword 0                        /* Sentinel value to indicate end of array */
+
+units_array:
+        .dword ohms
+        .dword kiloohms
+        .dword megaohms
+        .dword gigaohms
+        .dword 0                        /* Sentinel value to indicate end of array */
+
+.text
+.globl label
+
+color_code:
+        adrp    x1, color_array
+        add     x1, x1, :lo12:color_array
+        mov     x2, x1
+
+.next:
+        mov     x3, x0
+        ldr     x4, [x2], #8            /* load pointer, post-increment */
+
+.compare:
+        ldrb    w5, [x3], #1            /* load character, post-increment */
+        ldrb    w6, [x4], #1            /* load character, post-increment */
+        cmp     w5, w6
+        bne     .next
+
+        cbnz    w5, .compare
+
+        sub     x2, x2, #8
+        sub     x0, x2, x1
+        lsr     x0, x0, #3
+        ret
+
+/* extern void label(char *buffer, const char **colors); */
+label:
+        mov     x7, x0
+        mov     x8, x1
+        mov     x9, lr                 /* preserve return address */
+        mov     x10, #10
+        ldr     x0, [x8], #8           /* load address of first color */
+        bl      color_code
+        mov     w11, w0
+        ldr     x0, [x8], #8           /* load address of second color */
+        bl      color_code
+        mov     w12, w0
+        ldr     x0, [x8]               /* load address of third color */
+        bl      color_code
+        add     w0, w0, #1
+        mov     w3, #3
+        udiv    w2, w0, w3              /* quotient, indicates units */
+        msub    w4, w2, w3, w0          /* remainder */
+
+        cbz     w4, .divide
+
+        cbz     w11, .skip_first
+
+        add     w11, w11, #'0'
+        strb    w11, [x7], #1           /* write first digit */
+
+.skip_first:
+        add     w12, w12, #'0'
+        strb    w12, [x7], #1           /* write second digit */
+        cmp     w4, #1
+        beq     .append_units
+
+        mov     w12, #'0'
+        strb    w12, [x7], #1           /* write zero */
+        b .append_units
+
+.divide:
+        add     w11, w11, #'0'
+        strb    w11, [x7], #1           /* write first digit */
+        cbz     w12, .append_units
+
+        mov     w11, #'.'
+        strb    w11, [x7], #1           /* write '.' */
+        add     w12, w12, #'0'
+        strb    w12, [x7], #1           /* write second digit */
+
+.append_units:
+        adrp    x1, units_array
+        add     x1, x1, :lo12:units_array
+        lsl     w2, w2, #3
+        ldr     x2, [x1, x2]
+
+.copy:
+        ldrb    w3, [x2], #1
+        strb    w3, [x7], #1
+        cbnz    w3, .copy
+
+        mov     lr, x9
+        ret

exercises/practice/resistor-color-trio/.meta/tests.toml

@@ -0,0 +1,40 @@
+# 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.
+
+[d6863355-15b7-40bb-abe0-bfb1a25512ed]
+description = "Orange and orange and black"
+
+[1224a3a9-8c8e-4032-843a-5224e04647d6]
+description = "Blue and grey and brown"
+
+[b8bda7dc-6b95-4539-abb2-2ad51d66a207]
+description = "Red and black and red"
+
+[5b1e74bc-d838-4eda-bbb3-eaba988e733b]
+description = "Green and brown and orange"
+
+[f5d37ef9-1919-4719-a90d-a33c5a6934c9]
+description = "Yellow and violet and yellow"
+
+[5f6404a7-5bb3-4283-877d-3d39bcc33854]
+description = "Blue and violet and blue"
+
+[7d3a6ab8-e40e-46c3-98b1-91639fff2344]
+description = "Minimum possible value"
+
+[ca0aa0ac-3825-42de-9f07-dac68cc580fd]
+description = "Maximum possible value"
+
+[0061a76c-903a-4714-8ce2-f26ce23b0e09]
+description = "First two colors make an invalid octal number"
+
+[30872c92-f567-4b69-a105-8455611c10c4]
+description = "Ignore extra colors"