Lists

Lists

The Lists module provides comprehensive list manipulation and processing functions for the SCM programming language. This module includes:

• List operations: Basic operations like counting (count), accessing elements (nth), and type checking (list?)
• List construction: Building lists with append, cons, and unique operations (append_unique, merge_unique)
• List deconstruction: Extracting parts with car (head), cdr (tail), and filtering operations
• Functional programming: Higher-order functions like map, filter, reduce, and produce for advanced list processing
• List utilities: Searching (has?, contains?), merging, zipping, and flattening operations
• List generation: Creating sequences and ranges with produce and produceN functions

These functions provide the essential tools for working with lists as the primary data structure in functional programming with SCM.

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count

counts the number of elements in the list

Allowed number of parameters: 1–1

Parameters:

• list (list): base list

Returns: int

nth

get the nth item of a list

Allowed number of parameters: 2–2

Parameters:

• list (list): base list
• index (number): index beginning from 0

Returns: any

append

appends items to a list and return the extended list. The original list stays unharmed.

Allowed number of parameters: 2–1000

Parameters:

• list (list): base list
• item... (any): items to add

Returns: list

append_unique

appends items to a list but only if they are new. The original list stays unharmed.

Allowed number of parameters: 2–1000

Parameters:

• list (list): base list
• item... (any): items to add

Returns: list

cons

constructs a list from a head and a tail list

Allowed number of parameters: 2–2

Parameters:

• car (any): new head element
• cdr (list): tail that is appended after car

Returns: list

car

extracts the head of a list

Allowed number of parameters: 1–1

Parameters:

• list (list): list

Returns: any

cdr

extracts the tail of a list. The tail of a list is a list with all items except the head.

Allowed number of parameters: 1–1

Parameters:

• list (list): list

Returns: any

zip

swaps the dimension of a list of lists. If one parameter is given, it is a list of lists that is flattened. If multiple parameters are given, they are treated as the components that will be zipped into the sub list

Allowed number of parameters: 1–1000

Parameters:

• list (list): list of lists of items

Returns: list

merge

flattens a list of lists into a list containing all the subitems. If one parameter is given, it is a list of lists that is flattened. If multiple parameters are given, they are treated as lists that will be merged into one

Allowed number of parameters: 1–1000

Parameters:

• list (list): list of lists of items

Returns: list

merge_unique

flattens a list of lists into a list containing all the subitems. Duplicates are filtered out.

Allowed number of parameters: 1–1000

Parameters:

• list (list): list of lists of items

Returns: list

has?

checks if a list has a certain item (equal?)

Allowed number of parameters: 2–2

Parameters:

• haystack (list): list to search in
• needle (any): item to search for

Returns: bool

filter

returns a list that only contains elements that pass the filter function

Allowed number of parameters: 2–2

Parameters:

• list (list): list that has to be filtered
• condition (func): filter condition func(any)->bool

Returns: list

map

returns a list that contains the results of a map function that is applied to the list

Allowed number of parameters: 2–2

Parameters:

• list (list): list that has to be mapped
• map (func): map function func(any)->any that is applied to each item

Returns: list

mapIndex

returns a list that contains the results of a map function that is applied to the list

Allowed number of parameters: 2–2

Parameters:

• list (list): list that has to be mapped
• map (func): map function func(i, any)->any that is applied to each item

Returns: list

reduce

returns a list that contains the result of a map function

Allowed number of parameters: 2–3

Parameters:

• list (list): list that has to be reduced
• reduce (func): reduce function func(any any)->any where the first parameter is the accumulator, the second is a list item
• neutral (any): (optional) initial value of the accumulator, defaults to nil

Returns: any

produce

returns a list that contains produced items - it works like for(state = startstate, condition(state), state = iterator(state)) {yield state}

Allowed number of parameters: 3–3

Parameters:

• startstate (any): start state to begin with
• condition (func): func that returns true whether the state will be inserted into the result or the loop is stopped
• iterator (func): func that produces the next state

Returns: list

produceN

returns a list with numbers from 0..n-1

Allowed number of parameters: 1–1

Parameters:

• n (number): number of elements to produce

Returns: list

list?

checks if a value is a list

Allowed number of parameters: 1–1

Parameters:

• value (any): value to check

Returns: bool

contains?

checks if a value is in a list; uses the equal?? operator

Allowed number of parameters: 2–2

Parameters:

• list (list): list to check
• value (any): value to check

Returns: bool