Scan Higher Order Function Assignment

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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 Smlnj-logo.png
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