array_higher_order.ruff

# Array Higher-Order Functions Example
# Demonstrates map, filter, reduce, and find with practical use cases

print("=== Array Higher-Order Functions ===")
print()

# ============================================================================
# MAP - Transform each element
# ============================================================================
print("1. MAP - Transform elements")
print("   Applies a function to each element, returning a new array")
print()

# Example 1: Square numbers
numbers := [1, 2, 3, 4, 5]
squared := map(numbers, func(x) {
    return x * x
})
print("   Square numbers:")
print("   Input:  ", numbers)
print("   Output: ", squared)
print()

# Example 2: Convert temperatures from Celsius to Fahrenheit
celsius := [0, 10, 20, 30, 40]
fahrenheit := map(celsius, func(c) {
    return c * 9 / 5 + 32
})
print("   Celsius to Fahrenheit:")
print("   Celsius:    ", celsius)
print("   Fahrenheit: ", fahrenheit)
print()

# Example 3: String manipulation
names := ["alice", "bob", "charlie"]
capitalized := map(names, func(name) {
    return to_upper(name)
})
print("   Capitalize names:")
print("   Input:  ", names)
print("   Output: ", capitalized)
print()

# ============================================================================
# FILTER - Select elements matching a condition
# ============================================================================
print("2. FILTER - Select matching elements")
print("   Returns only elements where the function returns true")
print()

# Example 1: Filter even numbers
all_numbers := [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
evens := filter(all_numbers, func(n) {
    return n % 2 == 0
})
print("   Even numbers:")
print("   Input:  ", all_numbers)
print("   Output: ", evens)
print()

# Example 2: Filter positive numbers
mixed := [-5, 3, -2, 8, -1, 10]
positives := filter(mixed, func(n) {
    return n > 0
})
print("   Positive numbers:")
print("   Input:  ", mixed)
print("   Output: ", positives)
print()

# Example 3: Filter strings by length
words := ["a", "hello", "hi", "world", "ok", "programming"]
long_words := filter(words, func(word) {
    return len(word) > 2
})
print("   Words longer than 2 characters:")
print("   Input:  ", words)
print("   Output: ", long_words)
print()

# ============================================================================
# REDUCE - Accumulate values into a single result
# ============================================================================
print("3. REDUCE - Accumulate values")
print("   Combines all elements into a single value")
print()

# Example 1: Sum of numbers
values := [1, 2, 3, 4, 5]
sum := reduce(values, 0, func(acc, x) {
    return acc + x
})
print("   Sum of array:")
print("   Input: ", values)
print("   Sum:   ", sum)
print()

# Example 2: Product of numbers
factors := [2, 3, 4, 5]
product := reduce(factors, 1, func(acc, x) {
    return acc * x
})
print("   Product of array:")
print("   Input:   ", factors)
print("   Product: ", product)
print()

# Example 3: Join strings
words2 := ["Ruff", "is", "awesome"]
sentence := reduce(words2, "", func(acc, word) {
    if acc == "" {
        return word
    }
    return acc + " " + word
})
print("   Join words into sentence:")
print("   Input:    ", words2)
print("   Sentence: ", sentence)
print()

# Example 4: Find maximum value
data := [42, 15, 88, 23, 67, 91, 5]
max_value := reduce(data, 0, func(acc, x) {
    if x > acc {
        return x
    }
    return acc
})
print("   Find maximum:")
print("   Input: ", data)
print("   Max:   ", max_value)
print()

# ============================================================================
# FIND - Locate first matching element
# ============================================================================
print("4. FIND - Locate first match")
print("   Returns the first element where the function returns true")
print()

# Example 1: Find first number greater than threshold
nums := [3, 7, 12, 18, 24]
first_above_10 := find(nums, func(n) {
    return n > 10
})
print("   First number > 10:")
print("   Input:  ", nums)
print("   Found:  ", first_above_10)
print()

# Example 2: Find string starting with specific letter
fruits := ["apple", "banana", "cherry", "date", "elderberry"]
starts_with_c := find(fruits, func(fruit) {
    return starts_with(fruit, "c")
})
print("   First fruit starting with 'c':")
print("   Input: ", fruits)
print("   Found: ", starts_with_c)
print()

# Example 3: Find not found (returns 0)
small_nums := [1, 2, 3, 4, 5]
large := find(small_nums, func(n) {
    return n > 100
})
print("   Find number > 100 (not found):")
print("   Input: ", small_nums)
print("   Found: ", large)
print()

# ============================================================================
# CHAINING - Combine multiple operations
# ============================================================================
print("5. CHAINING - Combine operations")
print("   Chain multiple higher-order functions together")
print()

# Example: Process data through multiple transformations
# Get even numbers, square them, then sum the results
original := [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
print("   Original array: ", original)

step1 := filter(original, func(n) {
    return n % 2 == 0
})
print("   After filter (evens): ", step1)

step2 := map(step1, func(n) {
    return n * n
})
print("   After map (squared): ", step2)

result := reduce(step2, 0, func(acc, n) {
    return acc + n
})
print("   After reduce (sum): ", result)
print()

# Compact version - all in one expression
compact_result := reduce(
    map(
        filter(original, func(n) { return n % 2 == 0 }),
        func(n) { return n * n }
    ),
    0,
    func(acc, n) { return acc + n }
)
print("   Compact version result: ", compact_result)
print()

# ============================================================================
# PRACTICAL EXAMPLES
# ============================================================================
print("6. PRACTICAL EXAMPLES")
print()

# Example 1: Process student scores
print("   Student score processing:")
scores := [45, 78, 92, 55, 88, 67, 94, 82]
print("   All scores:    ", scores)

passing_scores := filter(scores, func(score) {
    return score >= 60
})
print("   Passing (≥60): ", passing_scores)

average := reduce(passing_scores, 0, func(acc, score) {
    return acc + score
}) / len(passing_scores)
print("   Average:       ", average)
print()

# Example 2: Data validation
print("   Data validation:")
user_inputs := ["", "hello", "", "world", "", "test"]
print("   Raw inputs:    ", user_inputs)

valid_inputs := filter(user_inputs, func(input) {
    return len(input) > 0
})
print("   Valid inputs:  ", valid_inputs)

count := reduce(valid_inputs, 0, func(acc, _) {
    return acc + 1
})
print("   Valid count:   ", count)
print()

# Example 3: Price calculations
print("   Price calculations:")
prices := [19.99, 29.99, 39.99, 49.99]
print("   Original prices: ", prices)

# Apply 20% discount
discounted := map(prices, func(price) {
    return price * 0.8
})
print("   After 20% off:   ", discounted)

total := reduce(discounted, 0, func(acc, price) {
    return acc + price
})
print("   Total:           ", total)
print()

print("=== Complete! ===")