2021-02-05

list helpers.

part of sph-lib

currently also contains bindings for non-list pairs.

# syntax

## let*-list

like let*, but variable names enclosed in round brackets bind list elements.

binding is done like lambda and apply.

examples

(let*-list ((a 1) ((b c) (list 2 3))) (and (= 1 a) (= 2 b) (= 3 c)))

(let*-list (((a b . c) (list 1 2 3 4))) #t)

(sph list)

procedure: any->list a ->

any -> list

wraps a non-list argument in a list

procedure: compact a ->

list -> list

keep only true elements in list. removes all boolean false values

procedure: complement lists ... ->

list ... -> list

delete elements from the first list that are included in the other lists

procedure: complement-both a b ->

list list -> (list list)

delete elements in both lists that are included in both lists

procedure: consecutive f a [c] ->

procedure:{any -> any/boolean} list [procedure] -> (list:matches list:rest)

splits the list into two lists, the first being a list of all beginning elements of \"a\" that consecutively matched

\"f\", the second being the rest.

like srfi-1 span but the result is a list and not multiple return values

\"f\", the second being the rest.

like srfi-1 span but the result is a list and not multiple return values

procedure: contains-all? a values ->

list ... -> boolean

test if argument \"a\" contains all of the given values

procedure: contains-some? a values ->

list ... -> boolean

test if argument \"a\" contains any of the given values

procedure: contains? a value [member] ->

list any [procedure:{any list -> boolean/any}] -> boolean

return a boolean indicating if list \"a\" contains \"value\"

procedure: containsq? a value ->

true if list contains value.

comparison with eq?

comparison with eq?

procedure: containsv-some? a values ->

list list -> boolean

test if argument \"a\" contains any of the given values

procedure: containsv? a value ->

true if list contains value.

comparison with eqv?

comparison with eqv?

procedure: convolve a b ->

procedure: count-value value a [equal?] ->

any list -> integer

count occurences of \"value\" in list

procedure: count-value-with-limit value a [count-limit member] ->

any list [integer procedure:{any list -> boolean/any}] -> integer

like count-value but with an optional parameter for a count at which to stop counting

procedure: count-with-limit pred limit a ... ->

procedure integer list ... -> integer

like \"count\" but with an optional parameter for a count at which to stop counting

syntax: define-list name a ...

procedure: delete-duplicates-sorted a [equal-f preserve-order] ->

list [procedure:{any any -> boolean} boolean] -> list

delete duplicates from a sorted list using a more efficient algorithm than for unsorted lists

procedure: difference lists ... ->

list ... -> list

result in a list of elements not included in all given lists

procedure: difference-and-intersection lists ... ->

list ... -> (list list)

results in a list with two elements, one being the symmetric-difference between the given lists and one being the intersection.

that means one list of all elements that are included in all lists, and one list of elements that are not included in all lists.

it does both calculations in one step saving resources compared to making them in separate steps.

that means one list of all elements that are included in all lists, and one list of elements that are not included in all lists.

it does both calculations in one step saving resources compared to making them in separate steps.

procedure: difference-and-intersection-p equal-f lists ... ->

{any any -> boolean} list ... -> (list:difference list:intersection)

like difference+intersection but the predicate for comparing list elements can be specified

procedure: difference-p equal-f lists ... ->

{any any -> boolean} list ... -> list

like

procedure: drop* count a ->

like srfi-1 drop but with reversed argument order (like stream-drop from srfi-41) and

returns null if list contains less elements than count instead of raising an exception

returns null if list contains less elements than count instead of raising an exception

procedure: duplicates a ->

get a list of distinct values that occur more than once in the same list

procedure: each-first-middle-last first-f middle-f last-f a ... ->

procedure procedure procedure list ... ->

untested.

call \"first-f\" for the first element,

call \"last-f\" for the last element,

call \"middle-f\" for a list of all elements inbetween

call \"first-f\" for the first element,

call \"last-f\" for the last element,

call \"middle-f\" for a list of all elements inbetween

procedure: each-in-index-range f start end a ... ->

procedure integer integer list ... ->

untested.

call f only for elements in index range between \"start\" and \"end\" inclusively

call f only for elements in index range between \"start\" and \"end\" inclusively

procedure: each-slice f slice-length a ->

procedure:{list ->} integer list ->

apply f to each slice of slice-length elements from list.

procedure: each-with-index f a ... ->

procedure:{index element ... ->} list ... ->

apply f to each element and its index in list a

procedure: every-fold f state a ... ->

procedure:{any:state any:element ... -> any:next-state} list:elements ... -> any:state/false

like fold but results in false if any result of f is not a true value

procedure: every-map f a ... ->

procedure:{any -> any} list ... -> list/false

like map but results in false if any result of f is not a true value

procedure: every-or-index f a ... ->

procedure:{any ... -> boolean} list ... -> true/integer

true if \"f\" is true for all elements, otherwise the index of the element for which \"f\" was false

procedure: false-if-null a ->

procedure: filter-append-map f lists ... ->

apply filter-map and then apply append on the result

procedure: filter-produce f a ... ->

procedure list ...

apply \"f\" to each ordered combination of elements from lists, cartesian product, and return true results in a list.

supports multiple lists and treats non-list arguments as the single element of a list.

example:

(produce f (1 2) (4 5) 6)

is equivalent to

(list (f 1 4 6) (f 1 5 6) (f 2 4 6) (f 2 5 6))

apply \"f\" to each ordered combination of elements from lists, cartesian product, and return true results in a list.

supports multiple lists and treats non-list arguments as the single element of a list.

example:

(produce f (1 2) (4 5) 6)

is equivalent to

(list (f 1 4 6) (f 1 5 6) (f 2 4 6) (f 2 5 6))

procedure: first-intersection a b ->

list list -> any

give the first found element that is included in both lists

procedure: first-intersection-p equal-f a b ->

{any any -> boolean} list list -> any

like first-intersection but the procedure for comparing elements can be specified

procedure: first-or-false a ->

list -> any/false

give the first element of a list if it is not null, otherwise false

procedure: first-or-null a ->

results in the first element of a list if it is not null, otherwise null

procedure: flat? a ->

list -> boolean

true if the list does not contain a list

procedure: flatten a ->

list -> (non-list ...)

replace sublists with their content, resulting in a list that does not contain lists

procedure: fold* f a custom-state-values ... ->

procedure:{any:list-element any:state-value ... -> (any:state-value)} list any:state-value ... -> list:state-values

like fold but with multiple state values. the state values are updated by returning a list from a call to \"f\".

apply \"f\" to each element of \"a\" and the state-value elements that were given to

fold-multiple or subsequently the updated state-values from the previous call to \"f\"

apply \"f\" to each element of \"a\" and the state-value elements that were given to

fold-multiple or subsequently the updated state-values from the previous call to \"f\"

procedure: fold-c* f a custom-state-values ... ->

procedure:{any:list-element any:state-value ... -> (any:state-value)} list any:state-value ... -> list:state-values

like fold but with multiple state values. the state values are updated by returning a list from a call to \"f\".

apply \"f\" to each element of \"a\" and the state-value elements that were given to

fold-multiple or subsequently the updated state-values from the previous call to \"f\"

apply \"f\" to each element of \"a\" and the state-value elements that were given to

fold-multiple or subsequently the updated state-values from the previous call to \"f\"

procedure: fold-integers count init f ->

integer any {integer any -> any} -> any

fold over integers from 0 to count - 1

procedure: fold-multiple f a custom-state-values ... ->

procedure:{any:list-element any:state-value ... -> (any:state-value)} list any:state-value ... -> list:state-values

like fold but with multiple state values. the state values are updated by returning a list from a call to \"f\".

apply \"f\" to each element of \"a\" and the state-value elements that were given to

fold-multiple or subsequently the updated state-values from the previous call to \"f\"

apply \"f\" to each element of \"a\" and the state-value elements that were given to

fold-multiple or subsequently the updated state-values from the previous call to \"f\"

procedure: fold-multiple-c f a custom-state-values ... ->

procedure:{any:element procedure:continue:{list:next-pair any:state-value ...} any:state-value ... -> any} list any:state-value ... -> list

procedure: fold-multiple-right f a r ... ->

procedure list any ... -> any

like fold-multiple but works through the list elements from last to first

procedure: fold-right* f a r ... ->

procedure list any ... -> any

like fold-multiple but works through the list elements from last to first

procedure: fold-segments size f init a ->

integer {any:state element ... -> any:state} any:state list -> any

fold over each overlapping segment with length \"size\".

example:

(fold-segments f 2 #t (list 4 5 6 7))

fold over each overlapping segment with length \"size\".

example:

(fold-segments f 2 #t (list 4 5 6 7))

procedure: fold-slice slice-length f init a ->

integer procedure:{any:state any:element ... -> any} any list -> any:state

call f with each slice-length number of consecutive elements of a

procedure: fold-span filter-f f a ->

procedure:{any -> any/false} procedure:{list -> any} list -> any

fold over each list of elements that consecutively matched filter-f (utilising the \"span\" procedure)

procedure: fold-unless f stop? default init a ... ->

{any ... -> any} {any -> boolean/any} any any list ... -> any

like fold, but returns \"default\" if \"stop?\" is true

procedure: fold-unless-check-init f stop? default init a ... ->

procedure: fold-until f init stop? a ->

procedure any procedure:{any -> boolean} list -> any

end folding if \"stop?\" is true for a result and return the result

procedure: group-consecutive filter-f a ->

{any -> boolean} list -> list

wrap multiple elements that consecutively match \"filter-f\" in a list

procedure: group-split-at-matches start-group? a ->

procedure:{any -> boolean} list -> (list ...)

wrap consecutive elements in lists. elements for which \"start-group?\" is true become the first element of a new list.

example

(group-split-at-matches integer? (list \"a\" \"b\" 1 \"c\" \"d\" 2 \"e\"))

->

((\"a\" \"b\") (1 \"c\" \"d\") (2 \"e\"))

example

(group-split-at-matches integer? (list \"a\" \"b\" 1 \"c\" \"d\" 2 \"e\"))

->

((\"a\" \"b\") (1 \"c\" \"d\") (2 \"e\"))

procedure: improper-list-split-at-last a ->

pair:improper-list -> (list any:non-pair)

(1 2 . 3) -> ((1 2) 3)

procedure: insert-second a b ->

any list -> list

insert \"a\" as the second element into list \"b\"

procedure: interleave a value ->

list any -> list

inserts value in front of each element in \"a\" except the first element.

example: (interleave (list 1 2 3) 4) -> (1 4 2 4 3)

example: (interleave (list 1 2 3) 4) -> (1 4 2 4 3)

procedure: intersection lists ... ->

list ... -> list

result in a list of all elements which are contained in all given lists

procedure: intersection-p equal-f rest ... ->

procedure:{any any -> boolean} list ... -> list

like \"intersection\" but the predicate for comparing the list elements can be specified

procedure: iterate-three f a states ... ->

procedure:{list:prev any:current list:next any:state ... -> any:state ...} list any:state-init ... -> list:state

calls \"f\" for each list element, previous list elements and following list elements.

multiple custom values can be updated each call with the result of \"f\" which must be a list

multiple custom values can be updated each call with the result of \"f\" which must be a list

procedure: iterate-three-stop-end stop? end map-f a states ... ->

{list any list any ... -> boolean} {list any list any ... -> list:state-values}:after-stop? {list any list any ... -> list:state-values} list any ... -> any

like \"iterate-three\" but takes two additional procedures - one for stopping the iteration

after a \"map-f\" result, and one that is called for the last element or when \"stop?\" is true

after a \"map-f\" result, and one that is called for the last element or when \"stop?\" is true

syntax: let*-list (((name ...) a) rest ...) body ...

syntax: list-bind a lambda-formals body ...

bind elements of list \"a\" to \"lambda-formals\"

procedure: list-deselect a indices ->

list (integer ...) -> list

return a new, eventually smaller, list consisting of values not at specified indices

procedure: list-distribute a indices default ->

list (integer ...) any -> list

creates a new list with values from list a at positions indices. the value for \"no-element\" is set at indices

not included in the list indices. the length of indices must equal the length of a, and indices should not have duplicates.

not included in the list indices. the length of indices must equal the length of a, and indices should not have duplicates.

procedure: list-distribute-sorted a indices default ->

like list-distribute but faster. works only correctly for indices lists that are sorted ascending

procedure: list-index-value a value [equal-f] ->

get the index of value in list

procedure: list-indices f a ->

procedure:{any -> boolean} list -> (integer ...)

create a list of all indices for which f results in true

procedure: list-logical-condition? a ->

any -> boolean

true if \"a\" is a list-logical condition

procedure: list-logical-contains? a condition ->

list list -> boolean

test for value inclusion with a condition list like ([or/and/not] value/condition ...).

example:

(list-logical-contains? (list 1 2 3) (quote (and 2 3 (or 4 1 5) (not 8)))) -> #t

example:

(list-logical-contains? (list 1 2 3) (quote (and 2 3 (or 4 1 5) (not 8)))) -> #t

procedure: list-logical-match match-one? condition ->

procedure:{any -> boolean} list -> false/any:last-sub-condition-result

match a logical condition that is a possibly nested list with and/or/not symbol prefixes.

match-one? is called for each element in condition that is not a condition prefix.

returns false early if a required part of the condition does not match.

condition: ([symbol:and/or/not] any/condition ...)

example

(list-logical-match (l (b) (contains? somelist b)) (q (and 1 2 (or (and 3 4) (and 5 6)))))

match-one? is called for each element in condition that is not a condition prefix.

returns false early if a required part of the condition does not match.

condition: ([symbol:and/or/not] any/condition ...)

example

(list-logical-match (l (b) (contains? somelist b)) (q (and 1 2 (or (and 3 4) (and 5 6)))))

procedure: list-page a entry-count number lookahead c ->

list integer integer integer procedure:{list boolean:last-page? -> any} -> any

pass a list of \"entry-count\" elements at an offset of (* number entry-count),

eventually including \"lookahead\" number of elements if they are the last elements

and a boolean indicating if it is the last page to continuation procedure \"c\"

eventually including \"lookahead\" number of elements if they are the last elements

and a boolean indicating if it is the last page to continuation procedure \"c\"

procedure: list-prefix? a prefix ->

list list -> boolean

true if the given \"prefix\" elements exist in order at the beginning of list.

examples:

(list-prefix? (list 3 2 4) (list 3 1)) -> #f

(list-prefix? (list 3 2 4) (list 3 2)) -> #t

examples:

(list-prefix? (list 3 2 4) (list 3 1)) -> #f

(list-prefix? (list 3 2 4) (list 3 2)) -> #t

procedure: list-replace-last a replacement ->

list any/procedure:{any -> any} -> list

replace the last element in a list

procedure: list-replace-last-n n a replacement ->

list integer any/procedure:{any ... -> any/list} -> list

procedure: list-select a indices ->

list (integer ...) -> list

return a new list consisting of values at indices

procedure: list-set-add = list rest ... ->

Add to LIST any of the elements of REST not already in the list.

These elements are `cons'ed onto the start of LIST (so the return shares

a common tail with LIST), but the order they're added is unspecified.

The given `=' procedure is used for comparing elements, called

as `(@var{=} listelem elem)', i.e., the second argument is one of the

given REST parameters.

These elements are `cons'ed onto the start of LIST (so the return shares

a common tail with LIST), but the order they're added is unspecified.

The given `=' procedure is used for comparing elements, called

as `(@var{=} listelem elem)', i.e., the second argument is one of the

given REST parameters.

procedure: list-set-difference = list1 rest ... ->

procedure: list-set-equal? a ... ->

list ... -> boolean

true if all elements of the given lists appear in all others.

uses \"equal?\" for element equality comparison

uses \"equal?\" for element equality comparison

procedure: list-set-eqv? a ... ->

list ... -> boolean

like \"list-set-equal?\" but uses \"eqv?\" for element equality comparison

procedure: list-set-subset? = rest ... ->

procedure: list-set-union = rest ... ->

procedure: list-sort-by-list order a [accessor] ->

list list -> list

sort a list so the elements correspond to the order of elements in list \"order\".

elements not contained in \"order\" are moved to the end of the result list.

examples:

(list-sort-by-list (list 3 2 4) (list 4 2 3)) -> (3 2 4)

(list-sort-by-list (list 3 2 4) (list 4 5 2 3)) -> (3 2 4 5)

elements not contained in \"order\" are moved to the end of the result list.

examples:

(list-sort-by-list (list 3 2 4) (list 4 2 3)) -> (3 2 4)

(list-sort-by-list (list 3 2 4) (list 4 5 2 3)) -> (3 2 4 5)

procedure: list-sort-with-accessor less? accessor a ->

procedure:{any any -> boolean} procedure:{any:list-element -> any} list -> list

sort list by calling accessor for each argument before comparison. only the order of elements changes, the individual elements are not changed

procedure: list-suffix? a suffix ->

list list -> boolean

true if the given \"suffix\" elements exist in order at the end of list.

see also \"list-prefix?\"

see also \"list-prefix?\"

procedure: list-tail-ref a b ->

procedure: map-apply f a ... ->

procedure:{any ... -> any} (list ...) ... -> list

like map but the procedure is applied with elements of \"a\" as arguments.

instead of calling f like (f (list 1 2)) like \"map\" would do, f is called like (f 1 2)

example

(map-apply f (list (list 1 2) (list 3 4)))

instead of calling f like (f (list 1 2)) like \"map\" would do, f is called like (f 1 2)

example

(map-apply f (list (list 1 2) (list 3 4)))

procedure: map-c f lists ... ->

procedure:{procedure:{any:new-element -> any}:continue any:element ... -> any:last-result} list ... -> list

map over list with a procedure that when called with the current map result continues the mapping.

if the procedure is not called, the result of the current call will become the tail of the result list.

maps only the length of the shortest list if multiple lists are given

example

(map-c (l (c a) (if (> 3 a) (c (+ 1 a)) (list))) (list 1 2 3 4 5))

->

(2 3 4)

if the procedure is not called, the result of the current call will become the tail of the result list.

maps only the length of the shortest list if multiple lists are given

example

(map-c (l (c a) (if (> 3 a) (c (+ 1 a)) (list))) (list 1 2 3 4 5))

->

(2 3 4)

procedure: map-consecutive filter-f f a ->

{any -> boolean} {any any ... -> any} list -> list

\"f\" is called for and with every list of elements that consecutively matched \"filter-f\". at least two elements at a time

procedure: map-first f a ->

procedure list -> list

call \"f\" for the first element of list and replace the first element in the list with the result of \"f\".

replace-first

replace-first

procedure: map-fold f a init ... ->

procedure list any ... -> list any ...

procedure:{(list-element state ...) -> (list-element state ...)}

combination of map and fold.

call f with each list element and state values, which are set to init for the first call.

each call to f must return a list of: the mapped result element and one

element for each updated value of state.

example: (map-fold (l (a index) (list (+ a index) (+ 1 index))) (list 1 2 3) 0)

combination of map and fold.

call f with each list element and state values, which are set to init for the first call.

each call to f must return a list of: the mapped result element and one

element for each updated value of state.

example: (map-fold (l (a index) (list (+ a index) (+ 1 index))) (list 1 2 3) 0)

procedure: map-integers count f ->

integer procedure:{integer -> any} -> list

map over integers from 0 to count - 1

procedure: map-last-n n b f ->

procedure:{any ... -> any/(any ...)} list -> list

call f to replace the last n elements in list b.

if the result of f is a list it is spliced so that the

elements can be replaced with multiple elements

if the result of f is a list it is spliced so that the

elements can be replaced with multiple elements

procedure: map-map f a ... ->

procedure (list ...) ... -> list

given a list of lists, maps over the elements of lists.

like (map (l (a) (map f a) a))

like (map (l (a) (map f a) a))

procedure: map-one predicate f a ->

{any -> any}:predicate {any:element -> any} list -> list

apply f only to the first element that matches predicate.

all elements that do not match are mapped with the \"identity\" function

all elements that do not match are mapped with the \"identity\" function

procedure: map-segments size f a ->

integer procedure:{any ... -> any} list -> list

map over each overlapping segment of length len.

each segment is one step apart.

example: for (1 2 3 4) size 2 maps (1 2) (2 3) (3 4)

each segment is one step apart.

example: for (1 2 3 4) size 2 maps (1 2) (2 3) (3 4)

procedure: map-selected select? f a ... ->

procedure procedure list ... -> list

apply f only to elements for which \"select?\" is true. unmatched items are included in the result list.

if multiple lists are given, it works like \"map\" except that the elements from the multiple lists for one call that are not selected are saved as a list.

map-some/map-only

if multiple lists are given, it works like \"map\" except that the elements from the multiple lists for one call that are not selected are saved as a list.

map-some/map-only

procedure: map-slice slice-length f a ->

integer procedure:{any ... -> any} list -> list

call \"f\" with each \"slice-length\" number of consecutive elements of \"a\"

procedure: map-span filter-f f a ->

procedure:{any -> any/false} procedure:{any any ... -> any} list -> list

apply \"f\" to each list of elements that consecutively matched \"filter-f\".

an unpredictable number of arguments might be passed to f. with (lambda a body ...) a single list can still be accessed.

this allows for things like (map-span string? string-append a)

an unpredictable number of arguments might be passed to f. with (lambda a body ...) a single list can still be accessed.

this allows for things like (map-span string? string-append a)

procedure: map-unless f stop? default a ... ->

procedure stop? list -> list/boolean:false

{any -> any} {any -> boolean} list -> list/boolean

map unless \"stop?\" is true for a mapping-result. return an empty list or \"default\" if \"stop?\" was true

procedure: map-with-index f a ... ->

procedure:{integer:index any:element ... -> any} list ... -> list

procedure: pair->list a ->

pair -> list

syntax: pair-bind a (b c) body ...

bind the first and second value of \"a\" to \"b\" and \"c\" respectively.

ideally, maybe, lambda/apply should support (apply (lambda (a . b)) (pair 1 2))

ideally, maybe, lambda/apply should support (apply (lambda (a . b)) (pair 1 2))

procedure: pair-fold-multiple f a init ... ->

{pair any -> any} list any ... -> any

like fold-multiple but calling f with the pairs of list

procedure: pair-map f a ->

procedure list -> list

like map but not the list elements are passed to \"f\" but the pairs of the list.

for example (1 2 3) is just another notation for the pair notation (1 . (2 . (3 . ())))

instead of mapping (1 2 3) pair-map maps ((1 2 3) (2 3) (3))

for example (1 2 3) is just another notation for the pair notation (1 . (2 . (3 . ())))

instead of mapping (1 2 3) pair-map maps ((1 2 3) (2 3) (3))

procedure: pair-reverse a ->

pair -> pair

reverse the order of values in a pair.

example: (pair-reverse (pair 1 2)) -> (2 . 1)

example: (pair-reverse (pair 1 2)) -> (2 . 1)

procedure: pattern-match-min-length a ->

list -> integer

takes a flat list with symbols and ellipses and counts the required parts of a pattern with

symbols interpreted as matching any element and ellipses to match zero or many occurences of the previous element.

# examples

((a ...)) -> 0

((a a ...)) -> 1

((a ... b ...)) -> 0

((a ... b ... c d)) -> 2

symbols interpreted as matching any element and ellipses to match zero or many occurences of the previous element.

# examples

((a ...)) -> 0

((a a ...)) -> 1

((a ... b ...)) -> 0

((a ... b ... c d)) -> 2

procedure: produce f a ... ->

procedure: produce-unless f stop? default a b ->

{any any -> any} {any -> boolean} any list list -> false/any

produce two lists unless \"stop?\" is true for a production-result. if stop? is true, result in false

procedure: replace a select? replacement ->

list procedure any -> list

procedure: replace-at-once match? f a ->

procedure:{any -> boolean} procedure:{list:matched-elements -> list:replacements} list:source -> list

all elements matching \"match?\" are collected in a list and passed to \"f\".

the result of \"f\" is then used to replace the matched elements in source in order

the result of \"f\" is then used to replace the matched elements in source in order

procedure: replace-value a search-value replacement [equal-f] ->

list any any [procedure:{any any -> boolean}] -> list

procedure: simplify a ->

any/list -> list/pair/any

list with one element -> element

list with two non-pair elements -> pair

procedure: simplify-list a ->

list -> list

examples:

(((1 2))) -> (1 2)

(((1 2) (3))) -> ((1 2) (3))

removes extra nesting

(((1 2))) -> (1 2)

(((1 2) (3))) -> ((1 2) (3))

removes extra nesting

variable: sph-list-description

procedure: splice predicate a ->

{list -> boolean} list -> list

splice elements that are lists and match predicate

procedure: splice-last-list a ->

list -> list

if the last element is a list, append it to the previous elements.

example: (splice-last-list (1 2 (3 4))) -> (1 2 3 4)

example: (splice-last-list (1 2 (3 4))) -> (1 2 3 4)

procedure: split-at-last a ->

list -> (list list)

get a list with the list of the initial elements and a list with the last element

procedure: split-at-value a search-value [inclusiveness] ->

list any [symbol:exclusive/inclusive] -> (list:left list:right)

procedure: split-by-pattern pattern a ->

(symbol symbol/ellipsis:... ...) list -> (list:((key . values) ...):matches list:rest)

basic matcher that only supports matching single or repeated elements with multiple ellipses.

creates alist elements for variables in pattern that match elements in list \"a\".

the result is a list with two values: one for the match and one for the unmatched rest.

if pattern did not match, then both values are false. if pattern is null, matches is null and rest is the input list.

unlike other pattern matchers, \"pattern\" is a list and not syntax and so can be passed as a variable.

# example

(split-by-pattern (quote (a b ... c)) (list 1 2 3 4)) -> (((a . 1) (b 2 3) (c . 4)) ())

creates alist elements for variables in pattern that match elements in list \"a\".

the result is a list with two values: one for the match and one for the unmatched rest.

if pattern did not match, then both values are false. if pattern is null, matches is null and rest is the input list.

unlike other pattern matchers, \"pattern\" is a list and not syntax and so can be passed as a variable.

# example

(split-by-pattern (quote (a b ... c)) (list 1 2 3 4)) -> (((a . 1) (b 2 3) (c . 4)) ())

procedure: tail-or-null a ->

list -> list

return the tail of list or null if there is no tail which is

the case when list is null

the case when list is null

procedure: take* count a ->

like srfi-1 take but with reversed argument order (like stream-take from srfi-41) and

returns null if list contains less elements than count instead of raising an exception

returns null if list contains less elements than count instead of raising an exception

procedure: union a ... ->