Higher-Order Functions

Functional helpers that take other functions as arguments.

MAP(list, fn)

• Parameters: list – list of values, fn – function (value, index, list)
• Returns: new list with fn applied to each element
• Example: MAP([1,2], FN(v,_,_ -> v * 2)) → [2,4]

FILTER(list, fn)

• Parameters: list, fn – function returning truthy to keep
• Returns: list of values where fn returns truthy
• Example: FILTER([1,2], FN(v,_,_ -> v > 1)) → [2]

REDUCE(list, init, fn)

• Parameters: list, init – initial value, fn – (acc, value, index, list)
• Returns: accumulated result
• Example: REDUCE([1,2,3], 0, FN(acc,v,_,_ -> acc + v)) → 6

SOME(list, fn)

• Parameters: list, fn
• Returns: true if any element makes fn truthy
• Example: SOME([1,2], FN(v,_,_ -> v == 2)) → true

EVERY(list, fn)

• Parameters: list, fn
• Returns: true if all elements make fn truthy
• Example: EVERY([1,2], FN(v,_,_ -> v > 0)) → true

FIND(list, fn)

• Parameters: list, fn
• Returns: first value where fn is truthy or null
• Example: FIND([1,2], FN(v,_,_ -> v == 2)) → 2

APPLY(fn, ...args)

• Parameters: fn – function, additional arguments
• Returns: result of calling fn with arguments
• Example: APPLY(FN(x -> x + 1), 2) → 3

IS_FUNCTION(x)

• Parameters: x – value to test
• Returns: true if x is a function
• Example: IS_FUNCTION(FN(x->x)) → true