Functional programming in bash
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Introduction

This is a fork of ssledz's fun.sh library.

This is mainly for my own personal use cases. So I would recommend using ssledz's version instead. I mainly worked towards getting this library to mostly pass shellcheck, removed some functionality, and name deconflicted some of the functions with what I had in my system.

Quick start

#!/bin/bash
. <(test -e fun.sh || curl -Ls https://raw.githubusercontent.com/brandon-rozek/bash-fun/master/src/fun.sh > fun.sh; cat fun.sh)

seq 1 4 | sum

Functions overview

list_append divide take_while
list_drop drop_while factorial filter foldl
isint isempty isfile isnonzerofile isreadable iswritable
isdir list_join lambda list_last list_head list
list_tail list_zip list_map
mod multiply not
add list_prepend product ret
revers revers_str scanl splitc strip
stripl stripr subtract sum take
tup unlist λ

list/unlist

$ list 1 2 3
1
2
3

$ list 1 2 3 4 5 | unlist
1 2 3 4 5

list_take/list_drop/list_tail/list_head/list_last

$ list 1 2 3 4 | list_drop 2
3
4

$ list 1 2 3 4 5 | list_head
1

$ list 1 2 3 4 | list_tail
2
3
4

$ list 1 2 3 4 5 | list_last
5

$ list 1 2 3 4 5 | list_take 2
1
2

join

$ list 1 2 3 4 5 | list_join ,
1,2,3,4,5

map

$ seq 1 5 | list_map λ a . 'echo $((a + 5))'
6
7
8
9
10

$ list a b s d e | list_map λ a . 'echo $a$(echo $a | tr a-z A-Z)'
aA
bB
sS
dD
eE

$ list 1 2 3 | list_map tee
1
2
3

filter

$ seq 1 10 | filter even
2
4
6
8
10

foldl/foldr

$ list a b c d | foldl λ acc el . 'echo -n $acc-$el'
a-b-c-d
$ seq 1 4 | foldl λ acc el . 'echo $(($acc + $el))'
10
$ seq 1 4 | foldl λ acc el . 'echo $(multiply $(($acc + 1)) $el)'
64 # 1 + (1 + 1) * 2 + (4 + 1) * 3 + (15 + 1) * 4 = 64

tup/tupx/tupl/tupr

$ tup a 1
(a,1)

$ tup 'foo bar' 1 'one' 2
(foo bar,1,one,2)

$ tup , 1 3
(,,1,3)
$ echo tup a 1 | tupl
a

$ echo tup a 1 | tupr
1

$ tup 'foo bar' 1 'one' 2 | tupl
foo bar

$ tup 'foo bar' 1 'one' 2 | tupr
2

list_zip

$ list a b c d e f | list_zip $(seq 1 10)
(a,1)
(b,2)
(c,3)
(d,4)
(e,5)
(f,6)
$ list a b c d e f | list_zip $(seq 1 10) | list_last | tupr
6

not/isint/isempty

$ isint 42
true

$ list blah | isint
false

$ not true
false

$ not "isint 777"
false

$ list 1 2 "" c d 6 | filter λ a . 'isint $a'
1
2
6

$ list 1 2 "" c d 6 | filter λ a . 'not "isempty $a"'
1
2
c
d
6

isfile/isnonzerofile/isreadable/iswritable/isdir

$ touch /tmp/foo

$ isfile /tmp/foo
true

$ not iswritable /
true

$ files="/etc/passwd /etc/sudoers /tmp /tmp/foo /no_such_file"

$ list $files | filter λ a . 'isfile $a'
/etc/passwd
/etc/sudoers
/tmp/foo

$ list $files | filter λ a . 'isdir $a'
/tmp

$ list $files | filter λ a . 'isreadable $a'
/etc/passwd
/tmp
/tmp/foo

$ list $files | filter λ a . 'iswritable $a'
/tmp
/tmp/foo

$ list $files | filter λ a . 'isnonzerofile $a'
/etc/passwd
/etc/sudoers
/tmp

$ list $files | filter λ a . 'not isfile $a'
/tmp
/no_such_file

scanl

$ seq 1 5 | scanl lambda acc el . 'echo $(($acc + $el))'
1
3
6
10
15
$ seq 1 5 | scanl lambda a b . 'echo $(($a + $b))' | list_last
15

Examples

processNames() {

  uppercase() {
     local str=$1
     echo $(tr 'a-z' 'A-Z' <<< ${str:0:1})${str:1}
  }

  list $@ \
    | filter λ name . '[[ ${#name} -gt 1 ]] && ret true || ret false' \
    | list_map λ name . 'uppercase $name' \
    | foldl λ acc el . 'echo $acc,$el'

}

processNames adam monika s slawek d daniel Bartek j k
Adam,Monika,Slawek,Daniel,Bartek

Running tests

TODO: Need to change the tests here

cd test
./test_runner

Contribution guidelines

Feel free to ask questions in chat, open issues, or contribute by creating pull requests.

In order to create a pull request

  • checkout master branch
  • introduce your changes & bump version
  • submit pull request

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