2.9 KiB
| isHidden | menupriority | kind | created_at | title | author_name | author_uri |
|---|---|---|---|---|---|---|
| false | 1 | article | 2011-09-27T15:15:23+02:00 | Higher order function in zsh | Yann Esposito | yannesposito.com |
<%= blogimage("main.jpg","Title image") %>
begindiv(intro)
<%= tldr %> some simple implementation of higher order function for zsh.
enddiv
# for each directory in projects dir
for toProject in /path/to/projects/*(/N); do
# toProject is /path/to/projects/foo
# project become foo (:t for tail)
project=${toProject:t}
for toResource in $toProject/resources/*.gif(.N); do
convert $toResource ${toResource:r}.png
\rm -f $toResource
done
done
gif_to_png() { convert $1 ${1:r}.png && \rm -f $1 }
handle_resources() { map gif_to_png $1/resources/*.gif(.N) }
map handle_resources /path/to/projects/*(/N)
Before ⇒
for toProject in Projects/*; do
project=$toProject:t
if print -- project | grep -v s >/dev/null
then
print $project
for toResource in $toProject/*(.N); do
if print -- ${toResource:t} | grep $project >/dev/null; then
print -- "X $toResource"
fi
done
fi
done
After ⇒
contain_no_s() { print $1 | grep -v s }
function verify_file_name {
local project=$1:t
contains_project_name() { print $1:t | grep $project }
map "print -- X" $(filter contains_project_name $1/*(.N))
}
map show_project_matchin_file $( filter contain_no_s Projects/* )
Also, the first verstion is a bit easier to read. But the second one is clearly far superior in architecture. Why?
#!/usr/bin/env zsh
Provide higer-order functions
usage:
$ foo(){print "x: $1"}
$ map foo a b c d
x: a
x: b
x: c
x: d
function map {
local func_name=$1
shift
for elem in $@; print -- $(eval $func_name $elem)
}
$ bar() { print $(($1 + $2)) }
$ fold bar 0 1 2 3 4 5
15
-- but also
$ fold bar 0 $( seq 1 100 )
function fold {
if (($#<2)) {
print -- "ERROR fold use at least 2 arguments" >&2
return 1
}
if (($#<3)) {
print -- $2
return 0
} else {
local acc
local right
local func_name=$1
local init_value=$2
local first_value=$3
shift 3
right=$( fold $func_name $init_value $@ )
acc=$( eval "$func_name $first_value $right" )
print -- $acc
return 0
}
}
usage:
$ baz() { print $1 | grep baz }
$ filter baz titi bazaar biz
bazaar
function filter {
local predicate=$1
local result
typeset -a result
shift
for elem in $@; do
if eval $predicate $elem >/dev/null; then
result=( $result $elem )
fi
done
print $result
}