feat(examples): add p/moul/fp

examples/gno.land/p/moul/fp/fp.gno

@@ -0,0 +1,270 @@
+// Package fp provides functional programming utilities for Gno, enabling
+// transformations, filtering, and other operations on slices of interface{}.
+//
+// Example of chaining operations:
+//
+//	numbers := []interface{}{1, 2, 3, 4, 5, 6}
+//
+//	// Define predicates, mappers and reducers
+//	isEven := func(v interface{}) bool { return v.(int)%2 == 0 }
+//	double := func(v interface{}) interface{} { return v.(int) * 2 }
+//	sum := func(a, b interface{}) interface{} { return a.(int) + b.(int) }
+//
+//	// Chain operations: filter even numbers, double them, then sum
+//	evenNums := Filter(numbers, isEven)        // [2, 4, 6]
+//	doubled := Map(evenNums, double)           // [4, 8, 12]
+//	result := Reduce(doubled, sum, 0)          // 24
+//
+//	// Alternative: group by even/odd, then get even numbers
+//	byMod2 := func(v interface{}) interface{} { return v.(int) % 2 }
+//	grouped := GroupBy(numbers, byMod2)        // {0: [2,4,6], 1: [1,3,5]}
+//	evens := grouped[0]                        // [2,4,6]
+package fp
+
+// Mapper is a function type that maps an element to another element.
+type Mapper func(interface{}) interface{}
+
+// Predicate is a function type that evaluates a condition on an element.
+type Predicate func(interface{}) bool
+
+// Reducer is a function type that reduces two elements to a single value.
+type Reducer func(interface{}, interface{}) interface{}
+
+// Filter filters elements from the slice that satisfy the given predicate.
+//
+// Example:
+//
+//	numbers := []interface{}{-1, 0, 1, 2}
+//	isPositive := func(v interface{}) bool { return v.(int) > 0 }
+//	result := Filter(numbers, isPositive) // [1, 2]
+func Filter(values []interface{}, fn Predicate) []interface{} {
+	result := []interface{}{}
+	for _, v := range values {
+		if fn(v) {
+			result = append(result, v)
+		}
+	}
+	return result
+}
+
+// Map applies a function to each element in the slice.
+//
+// Example:
+//
+//	numbers := []interface{}{1, 2, 3}
+//	toString := func(v interface{}) interface{} { return fmt.Sprintf("%d", v) }
+//	result := Map(numbers, toString) // ["1", "2", "3"]
+func Map(values []interface{}, fn Mapper) []interface{} {
+	result := make([]interface{}, len(values))
+	for i, v := range values {
+		result[i] = fn(v)
+	}
+	return result
+}
+
+// Reduce reduces a slice to a single value by applying a function.
+//
+// Example:
+//
+//	numbers := []interface{}{1, 2, 3, 4}
+//	sum := func(a, b interface{}) interface{} { return a.(int) + b.(int) }
+//	result := Reduce(numbers, sum, 0) // 10
+func Reduce(values []interface{}, fn Reducer, initial interface{}) interface{} {
+	acc := initial
+	for _, v := range values {
+		acc = fn(acc, v)
+	}
+	return acc
+}
+
+// FlatMap maps each element to a collection and flattens the results.
+//
+// Example:
+//
+//	words := []interface{}{"hello", "world"}
+//	split := func(v interface{}) interface{} {
+//	    chars := []interface{}{}
+//	    for _, c := range v.(string) {
+//	        chars = append(chars, string(c))
+//	    }
+//	    return chars
+//	}
+//	result := FlatMap(words, split) // ["h","e","l","l","o","w","o","r","l","d"]
+func FlatMap(values []interface{}, fn Mapper) []interface{} {
+	result := []interface{}{}
+	for _, v := range values {
+		inner := fn(v).([]interface{})
+		result = append(result, inner...)
+	}
+	return result
+}
+
+// All returns true if all elements satisfy the predicate.
+//
+// Example:
+//
+//	numbers := []interface{}{2, 4, 6, 8}
+//	isEven := func(v interface{}) bool { return v.(int)%2 == 0 }
+//	result := All(numbers, isEven) // true
+func All(values []interface{}, fn Predicate) bool {
+	for _, v := range values {
+		if !fn(v) {
+			return false
+		}
+	}
+	return true
+}
+
+// Any returns true if at least one element satisfies the predicate.
+//
+// Example:
+//
+//	numbers := []interface{}{1, 3, 4, 7}
+//	isEven := func(v interface{}) bool { return v.(int)%2 == 0 }
+//	result := Any(numbers, isEven) // true (4 is even)
+func Any(values []interface{}, fn Predicate) bool {
+	for _, v := range values {
+		if fn(v) {
+			return true
+		}
+	}
+	return false
+}
+
+// None returns true if no elements satisfy the predicate.
+//
+// Example:
+//
+//	numbers := []interface{}{1, 3, 5, 7}
+//	isEven := func(v interface{}) bool { return v.(int)%2 == 0 }
+//	result := None(numbers, isEven) // true (no even numbers)
+func None(values []interface{}, fn Predicate) bool {
+	for _, v := range values {
+		if fn(v) {
+			return false
+		}
+	}
+	return true
+}
+
+// Chunk splits a slice into chunks of the given size.
+//
+// Example:
+//
+//	numbers := []interface{}{1, 2, 3, 4, 5}
+//	result := Chunk(numbers, 2) // [[1,2], [3,4], [5]]
+func Chunk(values []interface{}, size int) [][]interface{} {
+	if size <= 0 {
+		return nil
+	}
+	var chunks [][]interface{}
+	for i := 0; i < len(values); i += size {
+		end := i + size
+		if end > len(values) {
+			end = len(values)
+		}
+		chunks = append(chunks, values[i:end])
+	}
+	return chunks
+}
+
+// Find returns the first element that satisfies the predicate and a boolean indicating if an element was found.
+//
+// Example:
+//
+//	numbers := []interface{}{1, 2, 3, 4}
+//	isEven := func(v interface{}) bool { return v.(int)%2 == 0 }
+//	result, found := Find(numbers, isEven) // 2, true
+func Find(values []interface{}, fn Predicate) (interface{}, bool) {
+	for _, v := range values {
+		if fn(v) {
+			return v, true
+		}
+	}
+	return nil, false
+}
+
+// Reverse reverses the order of elements in a slice.
+//
+// Example:
+//
+//	numbers := []interface{}{1, 2, 3}
+//	result := Reverse(numbers) // [3, 2, 1]
+func Reverse(values []interface{}) []interface{} {
+	result := make([]interface{}, len(values))
+	for i, v := range values {
+		result[len(values)-1-i] = v
+	}
+	return result
+}
+
+// Zip combines two slices into a slice of pairs. If the slices have different lengths,
+// extra elements from the longer slice are ignored.
+//
+// Example:
+//
+//	a := []interface{}{1, 2, 3}
+//	b := []interface{}{"a", "b", "c"}
+//	result := Zip(a, b) // [[1,"a"], [2,"b"], [3,"c"]]
+func Zip(a, b []interface{}) [][2]interface{} {
+	length := min(len(a), len(b))
+	result := make([][2]interface{}, length)
+	for i := 0; i < length; i++ {
+		result[i] = [2]interface{}{a[i], b[i]}
+	}
+	return result
+}
+
+// Unzip splits a slice of pairs into two separate slices.
+//
+// Example:
+//
+//	pairs := [][2]interface{}{{1,"a"}, {2,"b"}, {3,"c"}}
+//	numbers, letters := Unzip(pairs) // [1,2,3], ["a","b","c"]
+func Unzip(pairs [][2]interface{}) ([]interface{}, []interface{}) {
+	a := make([]interface{}, len(pairs))
+	b := make([]interface{}, len(pairs))
+	for i, pair := range pairs {
+		a[i] = pair[0]
+		b[i] = pair[1]
+	}
+	return a, b
+}
+
+// GroupBy groups elements based on a key returned by a Mapper.
+//
+// Example:
+//
+//	numbers := []interface{}{1, 2, 3, 4, 5, 6}
+//	byMod3 := func(v interface{}) interface{} { return v.(int) % 3 }
+//	result := GroupBy(numbers, byMod3) // {0: [3,6], 1: [1,4], 2: [2,5]}
+func GroupBy(values []interface{}, fn Mapper) map[interface{}][]interface{} {
+	result := make(map[interface{}][]interface{})
+	for _, v := range values {
+		key := fn(v)
+		result[key] = append(result[key], v)
+	}
+	return result
+}
+
+// Flatten flattens a slice of slices into a single slice.
+//
+// Example:
+//
+//	nested := [][]interface{}{{1,2}, {3,4}, {5}}
+//	result := Flatten(nested) // [1,2,3,4,5]
+func Flatten(values [][]interface{}) []interface{} {
+	result := []interface{}{}
+	for _, v := range values {
+		result = append(result, v...)
+	}
+	return result
+}
+
+// Helper functions
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}