Scan Higher Order Function Assignment

Background

Previously, we have built sum_scan. This is a specific version of scan where the operation is +. We will build a higher-order function scan which takes an operation to apply, as well as a list.

Code To Implement

file:	src/main/sml/warmup_scan/scan.sml
functions:	scan

val scan = fn : ('a * 'a -> 'a) -> 'a list -> 'a list

Note: this higher-order function is curried.

fun scan operation xs

Clients

int

scan op+

For example:

scan op+ [131,231,425]

would produce:

[131, 362, 787]

xs	131	231	425
scan op+ xs	131	362	787

scan op*

For example:

scan op* [131,231,425]

would produce:

[131, 30261, 12860925]

xs	131	231	425
scan op* xs	131	30261	12860925

set

scan intersection

For example:

scan intersection [fromList([1,2,3,4,5]), fromList([2,3,4]), fromList([0,1,2]), fromList([231,425])]

would produce:

[fromList([1,2,3,4,5]), fromList([2,3,4]), fromList([2]), empty]

xs	{1,2,3,4,5}	{2,3,4}	{0,1,2}	{231,425}
scan intersection xs	{1,2,3,4,5}	{2,3,4}	{2}	{}

scan union

For example:

scan intersection [fromList([1,2,3,4,5]), fromList([2,3,4]), fromList([0,1,2]), fromList([231,425])]

would produce:

[fromList([1,2,3,4,5]), fromList([1,2,3,4,5]), fromList([0,1,2,3,4,5]), fromList([0,1,2,3,4,5,231,425])]

xs	{1,2,3,4,5}	{2,3,4}	{0,1,2}	{231,425}
scan union xs	{1,2,3,4,5}	{1,2,3,4,5}	{0,1,2,3,4,5}	{0,1,2,3,4,5,231,425}

Test

file:	unit_test_scan.sml
source folder:	src/test/sml/warmup_scan