Functional bash, just a little :-) add to .bashrc: source fun.sh

fun.sh

#!/bin/bash
print() {
    while read x; do
        echo $x
    done
}

list() {
    for elem; do
        echo "$elem"
    done
}

unlist() {
    foldl λ a b → 'echo "$a $b"'
}

map() {
    while read x; do
        echo $x | $@
    done
}

foldl() {
    f="$@"
    read acc;
    while read elem; do
        acc="$(echo -e "$acc\n$elem" | $f)"
    done
    echo "$acc"
}

scanl() {
    f="$@"
    read acc
    while read elem; do
        acc="$(echo -e "$acc\n$elem" | $f)"
        echo "$acc"
    done
}

function lambda () {
    lam() {
        for last; do
            shift
            if [[ $last = "." || $last = ":" || $last = "->" || $last = "→" ]]; then
                echo "$@"
                return
            else
                echo "read $last;"
            fi
        done
    }
    y="stdin"
    for i in "$@"; do
        if [[ $i = "." || $i = ":" || $i = "->" || $i = "→" ]]; then
            y="args"
        fi
    done
    if [[ "$y" = "stdin" ]]; then
        read fun
        eval $(lam "$@ → $fun")
    else
        eval $(lam "$@")
    fi
}

### Let's define some "functional" functions :) ###
function λ() { lambda "$@"; }

sum() {
    foldl λ a b → 'echo $(($a + $b))'
}

product() {
    foldl λ a b → 'echo $(expr $a \* $b)'
}

factorial() {
    seq 1 $1 | product
}

special-lambda() {
    echo λ
}