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bash-fun

by ssledz

ssledz / bash-fun

Functional programming in bash

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Introduction

Introduction to fun.sh library

Quick start

#!/bin/bash
.  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

$ list 1 2 3
1
2
3


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

take/drop/ltail/lhead/last

$ 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

$ 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

$ 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

$ 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

$ seq 1 10 | filter λ a . '[[ $(mod $a 2) -eq 0 ]] && ret true || ret false'
2
4
6
8
10

foldl/foldr

$ 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

$ seq 1 4 | foldl λ acc el . 'echo $(($acc + $el))'
10

$ 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

$ tup a 1
(a,1)


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


$ tup , 1 3
(u002c,1,3)

$ 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

$ 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

$ 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

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


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

buff

$ 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

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

$ list a b c d e f | lzip $(seq 1 10) | last | tupr
6

curry

add2() {
    echo $(($1 + $2))
}

$ curry inc add2 1

$ inc 2
3


$ seq 1 3 | map λ a . 'inc $a'
2
3
4

peek

$ 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

$ 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

$ list Hello | maybe
(Just,Hello)


$ list "   " | maybe
(Nothing)


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


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



try/catch


$ 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

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

$ echo 'expr 2 / 2' | catch λ _ _ val . 'tupl $val'
1



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))' | last
15



with_trampoline/res/call


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


}

$ time factorial 30 | fold -w 70
265252859812191058636308480000000


real    0m1.854s
user    0m0.072s
sys     0m0.368s

time factorial 60 | fold -w 70
8320987112741390144276341183223364380754172606361245952449277696409600
000000000000


real    0m3.635s
user    0m0.148s
sys     0m0.692s

$ time factorial 90 | fold -w 70
1485715964481761497309522733620825737885569961284688766942216863704985
393094065876545992131370884059645617234469978112000000000000000000000


real    0m4.371s
user    0m0.108s
sys     0m0.436s



Examples


processNames() {


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


  list [email protected] 
    | 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

Adam,Monika,Slawek,Daniel,Bartek



Running tests


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

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