[Concept] String Functions - add exercise templates

docs/exercises.md

@@ -49,6 +49,8 @@ title: Exercises
     <li>25_range_iterators - Range over Iterators</li>
     <li>26_errors - Error Handling</li>
     <li>27_custom_errors - Custom Errors</li>
+    <li>41_regex - Regular Expressions</li>
+    <li>42_string_functions - String Functions</li>
     <li>36_json - JSON Processing</li>
     <li>37_xml - XML Processing</li>
   </ul>

internal/exercises/catalog.yaml

@@ -169,20 +169,19 @@ concepts:
   test_regex: ".*"
   hints:
     - Use `make(chan T, N)` to create a buffered channel and `<-` to send and receive on it.
-- slug: 39_channel_directions
-  title: Channel Directions
-  test_regex: ".*"
-  hints:
-    - Create two channels, one for sending jobs and one for receiving results.
-    - Start 5 workers using go routines.
-    - Send 50 jobs to the worker pool.
-    - Receive results from the worker pool and store them in a `rs` slice.
-    - Enforce type safety by specifying the channel directions in worker function.
 - slug: 35_channel_sync
   title: Channel Synchronization
   test_regex: ".*"
   hints:
     - Use a buffered boolean channel and wait till go routine completes.
+- slug: 36_json
+  title: JSON
+  test_regex: ".*"
+  hints:
+    - Use the encoding/json package to work with JSON data.
+    - Implement MarshalPerson to convert a struct into JSON using json.Marshal.
+    - Implement UnmarshalPerson to convert a JSON string into a struct using json.Unmarshal.
+    - Handle and return errors properly in both functions.
 - slug: 37_xml
   title: XML Encoding and Decoding
   test_regex: ".*"
@@ -191,12 +190,60 @@ concepts:
     - Add XML struct tags using `xml:"fieldname"` to map struct fields to XML elements.
     - Use xml.Marshal to convert structs to XML bytes.
     - Use xml.Unmarshal to parse XML bytes into structs.
+- slug: 37_sorting_by_functions
+  title: "Sorting by Functions"
+  difficulty: beginner
+  topics: ["slices", "sorting", "functions"]
+  hints:
+      - "Implement sort.Interface with Len(), Less(), and Swap() methods"
+      - "Create custom slice types like ByName and ByAge (e.g., type ByName []Person)"
+      - "Use sort.Sort() to sort slices with your custom comparison logic"
+      - "Remember to make copies of slices to avoid modifying the original"
+- slug: 38_time_formatting
+  title: "Time Formatting"
+  difficulty: beginner
+  topics: ["time", "formatting", "parsing"]
+  hints:
+      - "Use time.Now().Format() to format current time with a specific layout"
+      - "Use time.Parse() to parse time strings with known layouts"
+      - "Use time.LoadLocation() to work with different timezones"
+      - "Extract time components using .Date() and .Clock() methods"
+- slug: 39_channel_directions
+  title: Channel Directions
+  test_regex: ".*"
+  hints:
+    - Create two channels, one for sending jobs and one for receiving results.
+    - Start 5 workers using go routines.
+    - Send 50 jobs to the worker pool.
+    - Receive results from the worker pool and store them in a `rs` slice.
+    - Enforce type safety by specifying the channel directions in worker function.
 - slug: 40_channel_select
   title: Channel Select
   test_regex: ".*"
   hints:
     - Use `select` to handle multiple channel operations concurrently.
     - Use `time.After` to simulate a 5 microsecond timeout.
+- slug: 41_regex
+  title: Regular Expressions
+  test_regex: ".*"
+  hints:
+    - Use regexp.MustCompile to create compiled regular expressions.
+    - Use MatchString to test if a string matches a pattern.
+    - Use FindAllString to extract all matches from text.
+    - Use ReplaceAllString to replace matches with new text.
+    - "Email regex: ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$"
+    - "Phone regex: ^\\(\\d{3}\\) \\d{3}-\\d{4}$"
+    - "Number regex: \\d+\\.?\\d*"
+    - "Vowel regex: [aeiouAEIOU]"
+- slug: 42_string_functions
+  title: String Functions
+  test_regex: ".*"
+  hints:
+    - Use strings.Contains to check if a substring exists in a string.
+    - Use strings.HasPrefix and strings.HasSuffix for prefix/suffix checking.
+    - Use strings.Index to find the position of a substring.
+    - Use strings.ToUpper and strings.ToLower for case conversion.
+    - Use strings.TrimSpace to remove leading and trailing whitespace.
 projects:
 - slug: 101_text_analyzer
   title: Text Analyzer (Easy)
@@ -238,40 +285,11 @@ projects:
   test_regex: ".*"
   hints:
     - Implement an in-memory key-value store with basic CRUD operations and optional persistence.
-- slug: 36_json
-  title: JSON
-  test_regex: ".*"
-  hints:
-    - Use the encoding/json package to work with JSON data.
-    - Implement MarshalPerson to convert a struct into JSON using json.Marshal.
-    - Implement UnmarshalPerson to convert a JSON string into a struct using json.Unmarshal.
-    - Handle and return errors properly in both functions.
-
 - slug: 109_epoch
   title: "Epoch Conversion"
   difficulty: beginner
   topics: ["time", "epoch", "unix"]
   hints:
     - "Use Go's `time.Unix()` to convert an epoch to time."
     - "Use `t.Unix()` to convert time back to epoch."
-    - "Remember Go’s `time.Parse` can help parse date strings."
-
-- slug: 37_sorting_by_functions
-  title: "Sorting by Functions"
-  difficulty: beginner
-  topics: ["slices", "sorting", "functions"]
-  hints:
-      - "Implement sort.Interface with Len(), Less(), and Swap() methods"
-      - "Create custom slice types like ByName and ByAge (e.g., type ByName []Person)"
-      - "Use sort.Sort() to sort slices with your custom comparison logic"
-      - "Remember to make copies of slices to avoid modifying the original"
-
-- slug: 38_time_formatting
-  title: "Time Formatting"
-  difficulty: beginner
-  topics: ["time", "formatting", "parsing"]
-  hints:
-      - "Use time.Now().Format() to format current time with a specific layout"
-      - "Use time.Parse() to parse time strings with known layouts"
-      - "Use time.LoadLocation() to work with different timezones"
-      - "Extract time components using .Date() and .Clock() methods"
+    - "Remember Go's `time.Parse` can help parse date strings."

internal/exercises/solutions/41_regex/regex.go

@@ -0,0 +1,37 @@
+package regex
+
+// Task:
+// Implement regular expression functions using Go's regexp package.
+//
+// 1. Implement IsValidEmail to validate email addresses using regex.
+// 2. Implement ExtractNumbers to extract all numbers from a string.
+// 3. Implement ReplaceVowels to replace all vowels with asterisks.
+// 4. Implement IsPhoneNumber to validate phone numbers in format (XXX) XXX-XXXX.
+
+// IsValidEmail should return true if the email address is valid.
+// A valid email should have the format: [email protected]
+func IsValidEmail(email string) bool {
+	// TODO: implement using regexp.MustCompile and MatchString
+	return false
+}
+
+// ExtractNumbers should return all numbers found in the input string.
+// Numbers can be integers or decimals (e.g., "123", "45.67").
+func ExtractNumbers(text string) []string {
+	// TODO: implement using regexp.FindAllString
+	return nil
+}
+
+// ReplaceVowels should replace all vowels (a, e, i, o, u) with asterisks.
+// Case-insensitive replacement.
+func ReplaceVowels(text string) string {
+	// TODO: implement using regexp.MustCompile and ReplaceAllString
+	return ""
+}
+
+// IsPhoneNumber should return true if the phone number matches format (XXX) XXX-XXXX.
+// Example: (123) 456-7890
+func IsPhoneNumber(phone string) bool {
+	// TODO: implement using regexp.MustCompile and MatchString
+	return false
+}

internal/exercises/solutions/42_string_functions/string_functions.go

@@ -0,0 +1,38 @@
+package string_functions
+
+import "strings"
+
+// Contains checks if substr is within s
+func Contains(s, substr string) bool {
+	return strings.Contains(s, substr)
+}
+
+// HasPrefix tests whether the string s begins with prefix
+func HasPrefix(s, prefix string) bool {
+	return strings.HasPrefix(s, prefix)
+}
+
+// HasSuffix tests whether the string s ends with suffix
+func HasSuffix(s, suffix string) bool {
+	return strings.HasSuffix(s, suffix)
+}
+
+// Index returns the index of the first instance of substr in s, or -1 if substr is not present in s
+func Index(s, substr string) int {
+	return strings.Index(s, substr)
+}
+
+// ToUpper returns s with all Unicode letters mapped to their upper case
+func ToUpper(s string) string {
+	return strings.ToUpper(s)
+}
+
+// ToLower returns s with all Unicode letters mapped to their lower case
+func ToLower(s string) string {
+	return strings.ToLower(s)
+}
+
+// TrimSpace returns s with all leading and trailing white space removed
+func TrimSpace(s string) string {
+	return strings.TrimSpace(s)
+}

internal/exercises/templates/41_regex/regex.go

@@ -0,0 +1,37 @@
+package regex
+
+// Task:
+// Implement regular expression functions using Go's regexp package.
+//
+// 1. Implement IsValidEmail to validate email addresses using regex.
+// 2. Implement ExtractNumbers to extract all numbers from a string.
+// 3. Implement ReplaceVowels to replace all vowels with asterisks.
+// 4. Implement IsPhoneNumber to validate phone numbers in format (XXX) XXX-XXXX.
+
+// IsValidEmail should return true if the email address is valid.
+// A valid email should have the format: [email protected]
+func IsValidEmail(email string) bool {
+	// TODO: implement using regexp.MustCompile and MatchString
+	return false
+}
+
+// ExtractNumbers should return all numbers found in the input string.
+// Numbers can be integers or decimals (e.g., "123", "45.67").
+func ExtractNumbers(text string) []string {
+	// TODO: implement using regexp.FindAllString
+	return nil
+}
+
+// ReplaceVowels should replace all vowels (a, e, i, o, u) with asterisks.
+// Case-insensitive replacement.
+func ReplaceVowels(text string) string {
+	// TODO: implement using regexp.MustCompile and ReplaceAllString
+	return ""
+}
+
+// IsPhoneNumber should return true if the phone number matches format (XXX) XXX-XXXX.
+// Example: (123) 456-7890
+func IsPhoneNumber(phone string) bool {
+	// TODO: implement using regexp.MustCompile and MatchString
+	return false
+}

internal/exercises/templates/41_regex/regex_test.go

@@ -0,0 +1,99 @@
+package regex
+
+import "testing"
+
+func TestIsValidEmail(t *testing.T) {
+	tests := []struct {
+		email    string
+		expected bool
+	}{
+		{"[email protected]", true},
+		{"[email protected]", true},
+		{"invalid-email", false},
+		{"@domain.com", false},
+		{"user@", false},
+		{"user@domain", false},
+		{"", false},
+	}
+
+	for _, test := range tests {
+		result := IsValidEmail(test.email)
+		if result != test.expected {
+			t.Errorf("IsValidEmail(%q) = %v, want %v", test.email, result, test.expected)
+		}
+	}
+}
+
+func TestExtractNumbers(t *testing.T) {
+	tests := []struct {
+		text     string
+		expected []string
+	}{
+		{"I have 123 apples and 45.67 oranges", []string{"123", "45.67"}},
+		{"The price is $99.99", []string{"99.99"}},
+		{"No numbers here", []string{}},
+		{"123", []string{"123"}},
+		{"12.34.56", []string{"12.34", "56"}},
+		{"", []string{}},
+	}
+
+	for _, test := range tests {
+		result := ExtractNumbers(test.text)
+		if len(result) != len(test.expected) {
+			t.Errorf("ExtractNumbers(%q) length = %d, want %d", test.text, len(result), len(test.expected))
+			continue
+		}
+		for i, num := range result {
+			if num != test.expected[i] {
+				t.Errorf("ExtractNumbers(%q)[%d] = %q, want %q", test.text, i, num, test.expected[i])
+			}
+		}
+	}
+}
+
+func TestReplaceVowels(t *testing.T) {
+	tests := []struct {
+		text     string
+		expected string
+	}{
+		{"hello", "h*ll*"},
+		{"HELLO", "H*LL*"},
+		{"Hello World", "H*ll* W*rld"},
+		{"bcdfg", "bcdfg"},
+		{"", ""},
+		{"aeiou", "*****"},
+		{"AEIOU", "*****"},
+	}
+
+	for _, test := range tests {
+		result := ReplaceVowels(test.text)
+		if result != test.expected {
+			t.Errorf("ReplaceVowels(%q) = %q, want %q", test.text, result, test.expected)
+		}
+	}
+}
+
+func TestIsPhoneNumber(t *testing.T) {
+	tests := []struct {
+		phone    string
+		expected bool
+	}{
+		{"(123) 456-7890", true},
+		{"(555) 123-4567", true},
+		{"(000) 000-0000", true},
+		{"123-456-7890", false},
+		{"(123)456-7890", false},
+		{"(123) 4567890", false},
+		{"123 456 7890", false},
+		{"(123) 456-789", false},
+		{"(12) 456-7890", false},
+		{"", false},
+	}
+
+	for _, test := range tests {
+		result := IsPhoneNumber(test.phone)
+		if result != test.expected {
+			t.Errorf("IsPhoneNumber(%q) = %v, want %v", test.phone, result, test.expected)
+		}
+	}
+}