combinators

Combinators grab-bag.

  1. combinators
  2. Documentation
    1. Section Combinators
      1. Usage
      2. left-section
      3. right-section
      4. crop-left
      5. crop-right
      6. reversed
      7. arguments-chain
      8. arguments-each
      9. arguments-all
    2. Sort Combinators
      1. Usage
      2. Examples
      3. group-by
      4. group/key
      5. make-less-than/key
      6. make-equal/key
    3. Logical Combinators
      1. Usage
      2. andf
      3. orf
    4. Uni Combinators
      1. Usage
      2. uni
      3. uni2
      4. uni3
      5. uni-each
      6. uni-all
    5. Bi Combinators
      1. Usage
      2. bi
      3. bi2
      4. bi3
      5. bi-each
      6. bi-all
    6. Tri Combinators
      1. Usage
      2. tri
      3. tri2
      4. tri3
      5. tri-each
      6. tri-all
    7. Stack Combinators
      1. Usage
      2. uni
      3. uni2
      4. uni3
      5. uni@
      6. bi
      7. bi2
      8. bi3
      9. bi@
      10. tri
      11. tri2
      12. tri3
      13. tri@
      14. dip
      15. dup
      16. dupd
      17. swap
      18. drop
      19. drop/2
  3. Notes
  4. Author
  5. Repository
  6. Version history
  7. License

Documentation

Section Combinators

Usage

 
(import section-combinators)

FUNC a procedure.

left-section

[procedure] (left-section FUNC ARG0 ...) => procedure

Returns a procedure that partially applies some of its arguments from the left.

ARG0 ... a prefix of the arguments for FUNC.

Returns a partially curried procedure.

right-section

[procedure] (right-section FUNC ARG0 ...) => procedure

Returns a procedure that partially applies some of its arguments from the right.

ARG0 ... a suffix of the arguments for FUNC.

Returns a partially curried procedure.

crop-left

[procedure] (crop-left FUNC N) => procedure

Returns a procedure that drops the N left arguments before applying FUNC.

crop-right

[procedure] (crop-right FUNC N) => procedure

Returns a procedure that drops the N right arguments before applying FUNC.

reversed

[procedure] (reversed FUNC) => procedure

Returns a procedure that reverses the arguments before applying FUNC.

arguments-chain

[procedure] (arguments-chain [FUNC0...]) => procedure

Returns a procedure that applies each FUNCi to result of the FUNCi+1. FUNCn is applied to the arguments.

Examples:

((arguments-chain f g h) arg...) -> (apply f (apply g (apply h arg...)))
((arguments-chain f) arg...) -> (apply f arg...)
((arguments-chain) arg...) -> (list arg...)

arguments-each

[procedure] (arguments-each [FUNC0...]) => procedure

Returns a procedure that calls each FUNCi to the ARGi. The result is returned as a list. The FUNC0... are re-used until the argument list is exhausted.

Examples:

((arguments-each f g h) a b c d e) -> (list (f a) (g b) (h c) (f d) (g e))
((arguments-each f g h) a b c) -> (list (f a) (g b) (h c))
((arguments-each) arg...) -> (list arg...)

arguments-all

[procedure] (arguments-all [FUNC0...]) => procedure

Returns a procedure that calls each FUNCi with all the arguments. The result is returned as a list.

Examples:

((arguments-all f g h) a b c) -> (list (f a b c) (g a b c) (h a b c))
((arguments-all) arg...) -> (list arg...)

Sort Combinators

Except for make-less-than/key and make-equal/key these are not combinators.

Usage

 
(import sort-combinators)

Examples

 
(group/key identity '(1 2 3 3 4 4 4)) ;=> ((1) (2) (3 3) (4 4 4))

(group/key car '((a 1) (a 2) (b 1)))  ;=> '(((a 1) (a 2)) ((b 1)))

(sort '(("a" . 1) ("z" . 3) ("b" . 2)) (make-less-than/key first string-ci<?)) ;=> (("a" . 1) ("b" . 2) ("z" . 3))

group-by

[procedure] (group-by FUNC [EQUALITY equal?]) => procedure

Returns a procedure that takes a list and groups the elements by some key attribute. Uses the single-argument FUNC to retrieve key values & the EQUALITY function to compare them.

group/key

[procedure] (group/key FUNC LYST [EQUALITY equal?])

Groups a LYST of elements by some key attribute. Uses the single-argument FUNC to retrieve key values & the EQUALITY function to compare them.

The LYST must be in sorted order with respect to the key!

Returns a list of grouped elements.

make-less-than/key

[procedure] (make-less-than/key FUNC [LESS-THAN <]) => {{procedure/2}}

Returns a two-argument procedure that uses the single-argument FUNC to retrieve key values & the two-argument LESS-THAN procedure to compare them.

make-equal/key

[procedure] (make-equal/key FUNC [EQUAL =]) => {{procedure/2}}

Returns a two-argument procedure that uses the single-argument FUNC to retrieve key values & the two-argument EQUAL procedure to compare them.

Logical Combinators

Usage

 
(import logical-combinators)

andf

[procedure] (andf OBJECT...)

Eager version of and.

Returns last (not #f) OBJECT when all OBJECT... are (not #f), #f otherwise.

orf

[procedure] (orf OBJECT...)

Eager version of or.

Returns first (not #f) OBJECT, #f otherwise.

Uni Combinators

C is a function.

F, G and H are function.

Usage

 
(import uni-combinators)

uni

[procedure] (uni C F) => procedure

Returns (lambda (X) (C (F X))).

uni2

[procedure] (uni2 C F) => procedure

Returns (lambda (X Y) (C (F X Y))).

uni3

[procedure] (uni3 C F) => procedure

Returns (lambda (X Y Z) (C (F X Y Z))).

uni-each

[procedure] (uni-each C F) => procedure

Same as uni.

uni-all

[procedure] (uni-all C F) => procedure

Returns (lambda XS (C (apply F XS))).

Bi Combinators

Usage

 
(import bi-combinators)

bi

[procedure] (bi C F G) => procedure

Returns (lambda (X) (C (F X) (G X))).

bi2

[procedure] (bi2 C F G) => procedure

Returns (lambda (X Y) (C (F X Y) (G X Y))).

bi3

[procedure] (bi3 C F G) => procedure

Returns (lambda (X Y Z) (C (F X Y Z) (G X Y Z))).

bi-each

[procedure] (bi-each C F) => procedure

Returns (lambda (X Y) (C (F X) (F Y))).

bi-all

[procedure] (bi-all C F G) => procedure

Returns (lambda XS (C (apply F XS) (apply G XS))).

Tri Combinators

Usage

 
(import tri-combinators)

tri

[procedure] (tri C F G H) => procedure

Returns (lambda (X) (C (F X) (G X) (H X))).

tri2

[procedure] (tri2 C F G H) => procedure

Returns (lambda (X Y) (C (F X Y) (G X Y) (H X Y))).

tri3

[procedure] (tri3 C F G H) => procedure

Returns (lambda (X Y Z) (C (F X Y Z) (G X Y Z) (H X Y Z))).

tri-each

[procedure] (tri-each C F) => procedure

Returns (lambda (X Y Z) (C (F X) (F Y) (F Z))).

tri-all

[procedure] (tri-all C F G H) => procedure

Returns (lambda XS (C (apply F XS) (apply G XS) (apply H XS))).

Stack Combinators

These treat the argument list as a FORTH-like stack.

The utility is probably low.

Usage

 
(import stack-combinators)

C is a function.

F, G and H are function.

X, Y and Z are object.

uni

[procedure] (uni X F C) => procedure

Returns the result of (C (F X)).

[procedure] (uni F C) => {{procedure/1}}
[procedure] (uni C) => {{procedure/1}}
[procedure] (uni) => {{procedure/1}}

Returns a curried procedure.

uni2

[procedure] (uni2 X Y F C) => procedure

Returns the result of (C (F X Y)).

[procedure] (uni2 F C) => {{procedure/2}}
[procedure] (uni2 C) => {{procedure/1}}
[procedure] (uni2) => {{procedure/1}}

Returns a curried procedure.

uni3

[procedure] (uni3 X Y Z F C) => procedure

Returns the result of (C (F X Y Z)).

[procedure] (uni3 F C) => {{procedure/3}}
[procedure] (uni3 C) => {{procedure/1}}
[procedure] (uni3) => {{procedure/1}}

Returns a curried procedure.

uni@

[procedure] (uni@ X F C) => procedure

Returns the result of (C (F X)).

[procedure] (uni@ F C) => {{procedure/1}}

Returns a curried procedure.

bi

[procedure] (bi X F G C) => procedure

Returns the result of (C (F X) (G X)).

[procedure] (bi F G C) => {{procedure/1}}
[procedure] (bi F G) => {{procedure/1}}
[procedure] (bi C) => {{procedure/2}}
[procedure] (bi) => {{procedure/1}}

Returns a curried procedure.

bi2

[procedure] (bi2 X Y F G C) => procedure

Returns the result of (C (F X Y) (G X Y)).

[procedure] (bi2 F G C) => {{procedure/2}}
[procedure] (bi2 F G) => {{procedure/1}}
[procedure] (bi2 C) => {{procedure/2}}
[procedure] (bi2) => {{procedure/1}}

Returns a curried procedure.

bi3

[procedure] (bi3 X Y Z F G C) => procedure

Returns the result of (C (F X Y Z) (G X Y Z)).

[procedure] (bi3 F G C) => {{procedure/3}}
[procedure] (bi3 F G) => {{procedure/1}}
[procedure] (bi3 C) => {{procedure/2}}
[procedure] (bi3) => {{procedure/1}}

Returns a curried procedure.

bi@

[procedure] (bi@ X Y F C) => procedure

Returns the result of (C (F X) (F Y)).

[procedure] (bi@ F C) => {{procedure/2}}

Returns a curried procedure.

tri

[procedure] (tri X F G H C) => procedure

Returns the result of (C (F X) (G X) (H X)).

[procedure] (tri F G H C) => {{procedure/1}}
[procedure] (tri F G H) => {{procedure/1}}
[procedure] (tri C) => {{procedure/3}}
[procedure] (tri) => {{procedure/1}}

Returns a curried procedure.

tri2

[procedure] (tri2 X Y F G H C) => procedure

Returns the result of (C (F X Y) (G X Y) (H X Y)).

[procedure] (tri2 F G H C) => {{procedure/2}}
[procedure] (tri2 F G H) => {{procedure/1}}
[procedure] (tri2 C) => {{procedure/3}}
[procedure] (tri2) => {{procedure/1}}

Returns a curried procedure.

tri3

[procedure] (tri3 X Y Z F G H C) => procedure

Returns the result of (C (F X Y Z) (G X Y Z) (H X Y Z)).

[procedure] (tri3 F G H C) => {{procedure/3}}
[procedure] (tri3 F G H) => {{procedure/1}}
[procedure] (tri3 C) => {{procedure/3}}
[procedure] (tri3) => {{procedure/1}}

Returns a curried procedure.

tri@

[procedure] (tri@ X Y Z F C) => procedure

Returns the result of (C (F X) (F Y) (F Z)).

[procedure] (tri@ F C) => {{procedure/3}}

Returns a curried procedure.

dip

[procedure] (dip X Y F C) => procedure

Returns the result of (C (F X) Y).

[procedure] (dip F C) => {{procedure/2}}

Returns a curried procedure.

dup

[procedure] (dup X C) => procedure

Returns the result of (C X X).

[procedure] (dup C) => {{procedure/1}}

Returns a curried procedure.

dupd

[procedure] (dupd X Y C) => procedure

Returns the result of (C X X Y).

[procedure] (dupd C) => {{procedure/2}}

Returns a curried procedure.

swap

[procedure] (swap X Y C) => procedure

Returns the result of (C Y X).

[procedure] (swap C) => {{procedure/2}}

Returns a curried procedure.

drop

[procedure] (drop X C) => procedure

Returns the result of (C).

[procedure] (drop C) => {{procedure/1}}

Returns a curried procedure.

drop/2

[procedure] (drop/2 X Y C) => procedure

Returns the result of (C X).

[procedure] (drop/2 C) => {{procedure/2}}

Returns a curried procedure.

Notes

Author

Kon Lovett

Repository

This egg is hosted on the CHICKEN Subversion repository:

https://anonymous@code.call-cc.org/svn/chicken-eggs/release/5/combinators

If you want to check out the source code repository of this egg and you are not familiar with Subversion, see this page.

Version history
1.2.0
Added uni/bi/tri-combinators & more section-combinators.
1.1.0
Added section-combinators.
1.0.0
Chicken 4 release.

License

Public Domain.