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https://github.com/ssledz/bash-fun

Functional programming in bash
https://github.com/ssledz/bash-fun

bash functional-programming

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Functional programming in bash

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README 

        
# Introduction



[Introduction to fun.sh library](http://ssledz.github.io/presentations/bash-fun.html#/)



# Quick start



```bash

#!/bin/bash

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



seq 1 4 | sum

```



# Functions overview

|||||||

|------|------|------|------|------|------|

|**append**|**buff**|**call**|**catch**|**curry**|**div**|

|**drop**|**dropw**|**factorial**|**filter**|**foldl**|**foldr**|

|**isint**|**isempty**|**isfile**|**isnonzerofile**|**isreadable**|**iswritable**|

|**isdir**|**join**|**lambda**|**last**|**lhead**|**list**|

|**ltail**|**lzip**|**map**|**maybe**|**maybemap**|**maybevalue**|

|**mod**|**mul**|**not**|**ntup**|**ntupl**|**ntupr**|

|**ntupx**|**peek**|**plus**|**prepend**|**product**|**ret**|

|**res**|**revers**|**revers_str**|**scanl**|**splitc**|**strip**|

|**stripl**|**stripr**|**sub**|**sum**|**take**|**try**|

|**tup**|**tupl**|**tupr**|**tupx**|**unlist**|**λ**|

|**with_trampoline**|



## *list/unlist*



```bash

$ list 1 2 3

1

2

3



$ list 1 2 3 4 5 | unlist

1 2 3 4 5

```



## *take/drop/ltail/lhead/last*



```bash

$ list 1 2 3 4 | drop 2

3

4



$ list 1 2 3 4 5 | lhead

1



$ list 1 2 3 4 | ltail

2

3

4



$ list 1 2 3 4 5 | last

5



$ list 1 2 3 4 5 | take 2

1

2

```



## *join*



```bash

$ list 1 2 3 4 5 | join ,

1,2,3,4,5



$ list 1 2 3 4 5 | join , [ ]

[1,2,3,4,5]

```



## *map*



```bash

$ seq 1 5 | map λ a . 'echo $((a + 5))'

6

7

8

9

10



$ list a b s d e | map λ a . 'echo $a$(echo $a | tr a-z A-Z)'

aA

bB

sS

dD

eE



$ list 1 2 3 | map echo

1

2

3



$ list 1 2 3 | map 'echo $ is a number'

1 is a number

2 is a number

3 is a number



$ list 1 2 3 4 | map 'echo \($,$\) is a point'

(1,1) is a point

(2,2) is a point

(3,3) is a point

(4,4) is a point

```



## *flat map*



```bash

$ seq 2 3 | map λ a . 'seq 1 $a' | join , [ ]

[1,2,1,2,3]



$ list a b c | map λ a . 'echo $a; echo $a | tr a-z A-z' | join , [ ]

[a,A,b,B,c,C]

```



## *filter*



```bash

$ seq 1 10 | filter λ a . '[[ $(mod $a 2) -eq 0 ]] && ret true || ret false'

2

4

6

8

10

```



## *foldl/foldr*



```bash

$ list a b c d | foldl λ acc el . 'echo -n $acc-$el'

a-b-c-d



$ list '' a b c d | foldr λ acc el .\

    'if [[ ! -z $acc ]]; then echo -n $acc-$el; else echo -n $el; fi'

d-c-b-a

```



```bash

$ seq 1 4 | foldl λ acc el . 'echo $(($acc + $el))'

10

```



```bash

$ seq 1 4 | foldl λ acc el . 'echo $(mul $(($acc + 1)) $el)'

64 # 1 + (1 + 1) * 2 + (4 + 1) * 3 + (15 + 1) * 4 = 64



$ seq 1 4 | foldr λ acc el . 'echo $(mul $(($acc + 1)) $el)'

56 # 1 + (1 + 1) * 4 + (8 + 1) * 3 + (27 + 1) * 2 = 56

```



## *tup/tupx/tupl/tupr*



```bash

$ tup a 1

(a,1)



$ tup 'foo bar' 1 'one' 2

(foo bar,1,one,2)



$ tup , 1 3

(u002c,1,3)

```



```bash

$ tupl $(tup a 1)

a



$ tupr $(tup a 1)

1



$ tup , 1 3 | tupl

,



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

foo bar



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

2

```



```bash

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

1



$ tup 'foo bar' 1 'one' 2 | tupx 1,3

foo bar

one



$ tup 'foo bar' 1 'one' 2 | tupx 2-4

1

one

2

```



## *ntup/ntupx/ntupl/ntupr*



```bash

$ ntup tuples that $(ntup safely nest)

(dHVwbGVzCg==,dGhhdAo=,KGMyRm1aV3g1Q2c9PSxibVZ6ZEFvPSkK)



echo '(dHVwbGVzCg==,dGhhdAo=,KGMyRm1aV3g1Q2c9PSxibVZ6ZEFvPSkK)' | ntupx 3 | ntupr

nest



$ ntup 'foo,bar' 1 one 1

(Zm9vLGJhcgo=,MQo=,b25lCg==,MQo=)



$ echo '(Zm9vLGJhcgo=,MQo=,b25lCg==,MQo=)' | ntupx 1

foo,bar

```



```bash

$ ntupl $(ntup 'foo bar' 1 one 2)

foo bar



$ ntupr $(ntup 'foo bar' 1 one 2)

2

```



## *buff*



```bash

$ seq 1 10 | buff λ a b . 'echo $(($a + $b))'

3

7

11

15

19



$ seq 1 10 | buff λ a b c d e . 'echo $(($a + $b + $c + $d + $e))'

15

40

```



## *lzip*



```bash

$ list a b c d e f | lzip $(seq 1 10)

(a,1)

(b,2)

(c,3)

(d,4)

(e,5)

(f,6)

```



```bash

$ list a b c d e f | lzip $(seq 1 10) | last | tupr

6

```



## *curry*



```bash

add2() {

    echo $(($1 + $2))

}

```



```bash

$ curry inc add2 1

```



```bash

$ inc 2

3



$ seq 1 3 | map λ a . 'inc $a'

2

3

4

```



## *peek*



```bash

$ list 1 2 3 \

    | peek lambda a . echo 'dbg a : $a' \

    | map lambda a . 'mul $a 2' \

    | peek lambda a . echo 'dbg b : $a' \

    | sum



dbg a : 1

dbg a : 2

dbg a : 3

dbg b : 2

dbg b : 4

dbg b : 6

12

```



```bash

$ a=$(seq 1 4 | peek lambda a . echo 'dbg: $a' | sum)



dbg: 1

dbg: 2

dbg: 3

dbg: 4



$ echo $a



10

```



## *maybe/maybemap/maybevalue*



```bash

$ list Hello | maybe

(Just,Hello)



$ list "   " | maybe

(Nothing)



$ list Hello | maybe | maybemap λ a . 'tr oH Oh <<<$a'

(Just,hellO)



$ list "   " | maybe | maybemap λ a . 'tr oH Oh <<<$a'

(Nothing)



$ echo bash-fun rocks | maybe | maybevalue DEFAULT

bash-fun rocks



$ echo | maybe | maybevalue DEFAULT

DEFAULT



```



## *not/isint/isempty*



```bash

$ 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*



```bash

$ 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

```



## *try/catch*



```bash

$ echo 'expr 2 / 0' | try λ _ . 'echo 0'

0



$ echo 'expr 2 / 0' | try λ status . 'echo $status'

2



$ echo 'expr 2 / 2' | try λ _ . 'echo 0'

1

```



```bash

try λ  _ . 'echo some errors during pull; exit 1' < <(echo git pull)

```



```bash

$ echo 'expr 2 / 0' \

    | LANG=en catch λ cmd status val . 'echo cmd=$cmd,status=$status,val=$val'

cmd=expr 2 / 0,status=2,val=(expr:,division,by,zero)

```



```bash

$ echo 'expr 2 / 2' | catch λ _ _ val . 'tupl $val'

1

```



## *scanl*



```bash

$ seq 1 5 | scanl lambda acc el . 'echo $(($acc + $el))'

1

3

6

10

15

```



```bash

$ seq 1 5 | scanl lambda a b . 'echo $(($a + $b))' | last

15

```



## *with_trampoline/res/call*



```bash

factorial() {

    fact_iter() {

        local product=$1

        local counter=$2

        local max_count=$3

        if [[ $counter -gt $max_count ]]; then

            res $product

        else

            call fact_iter $(echo $counter\*$product | bc) $(($counter + 1)) $max_count

        fi

    }



    with_trampoline fact_iter 1 1 $1

}

```



```bash

$ time factorial 30 | fold -w 70

265252859812191058636308480000000



real    0m1.854s

user    0m0.072s

sys     0m0.368s

```



```bash

time factorial 60 | fold -w 70

8320987112741390144276341183223364380754172606361245952449277696409600

000000000000



real    0m3.635s

user    0m0.148s

sys     0m0.692s

```



```bash

$ time factorial 90 | fold -w 70

1485715964481761497309522733620825737885569961284688766942216863704985

393094065876545992131370884059645617234469978112000000000000000000000



real    0m4.371s

user    0m0.108s

sys     0m0.436s

```



# Examples



```bash

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' \

    | map λ name . 'uppercase $name' \

    | foldl λ acc el . 'echo $acc,$el'



}



processNames adam monika s slawek d daniel Bartek j k

```



```bash

Adam,Monika,Slawek,Daniel,Bartek

```



# Running tests



```bash

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



# Resources

* [Inspiration](https://quasimal.com/posts/2012-05-21-funsh.html)

* [Functional Programming in Bash](https://medium.com/@joydeepubuntu/functional-programming-in-bash-145b6db336b7)