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Procs are shell like-functions, but they can have parameters, and lack dynamic scope.
proc foo(x) {
echo "[$x]"
}
foo bar # prints [bar]
Blocks are fragments of code within { } that can be passed to builtins (and
eventually procs):
cd /tmp {
echo $PWD # prints /tmp
}
echo $PWD # prints original dir
Shell-like open procs that accept arbitrary numbers of arguments:
proc open {
write 'args are' @ARGV
}
# All valid:
open
open 1
open 1 2
Stricter closed procs:
proc closed(x) {
write 'arg is' $x
}
closed # runtime error: missing argument
closed 1 # valid
closed 1 2 # runtime error: too many arguments
TODO:
'' to null for string argument defaults.@ is "splice" at the call site. Or also "rest" parameters.: for ref params& for blocks?
These forms work:
cd / {
echo $PWD
}
cd / { echo $PWD }
cd / { echo $PWD }; cd / { echo $PWD }
These are syntax errors:
a=1 { echo bad }; # assignments can't take blocks
>out.txt { echo bad }; # bare redirects can't take blocks
break { echo bad }; # control flow can't take blocks
Runtime error:
local a=1 { echo bad }; # assignment builtins can't take blocks
Caveat: Blocks Are Space Sensitive
cd {a,b} # brace substitution
cd { a,b } # tries to run command 'a,b', which probably doesn't exist
Quoting of { } obeys the normal rules:
echo 'literal braces not a block' \{ \}
echo 'literal braces not a block' '{' '}'
TODO: This section has to be implemented and tested.
yield keyword?)proc p(&block) {
echo '>'
$block # call it?
# or maybe just 'block' -- it's a new word in the "proc" namespace?
echo '<'
}
# Invoke it
p {
echo 'hello'
}
# Output:
# >
# hello
# <
How to get the value?
var namespace = evalblock('name', 1+2, up=1)
# _result is set if there was a return statement!
# namespace has all vars except those prefixed with _
var result = namespace->_result
TODO: Subinterpreters?
return? What about break?return accepts Oil expressions (not shell-like words) ?Can block can set vars in enclosing scope?
setref('name', 1+2, up=1)
Evaluates to JSON (like YAML and TOML):
server foo {
port = 80
}
And can also be serialized as command line flags.
Replaces anti-patterns:
BEGIN {
end
}
when x {
}
rule foo.c : foo.bar {
cc -o out @srcs
}
Probably use a block format. Compare with Python's optparse.o
See issue.
Haven't decided on this yet.
check {
}
In addition to shell-like procs, Oil also has Python-like functions:
var x = len(ARGV) + 1
For now, we only have a few builtin functions like len().
There are two kinds of composition / code units in Oil:
argv array and returning exit code. I think of proc as procedure or
process.procs are called with a "command line":
myproc arg1 arg2 arg3
funcs are called with Python/JS-like Oil expressions:
var x = myfunc(42, 'foo')
do myfunc(42, 'foo') # throw away the return value.
This is NOT legal:
myfunc(42, 'foo')
TODO:
Shell is really the "main", if that makes sense. procs can call funcs, but
funcs won't be able to call procs (except for some limited cases like log and
die).
People may tend to prefer funcs because they're more familiar. But shell composition with proc is very powerful!
They have at least two kinds of composition that functions don't have. See #shell-the-good-parts on Bernstein chaining and "point-free" pipelines.
Here are some complicated examples from the tests. It's not representative of what real code looks like, but it shows all the features.
proc:
proc name-with-hyphen (x, y, @names) {
echo $x $y
echo names: @names
}
name-with-hyphen a b c
func:
shopt -s oil:basic
func f(a, b=0, ...args; c, d=0, ...named) {
echo __ args: @args
echo __ named:
echo @named | sort
if (named) {
return [a, b, c, d]
} else {
return a + b + c + d
}
}
var a = [42, 43]
var n = {x: 99, y: 100}
echo ____
echo string $f(0, 1, ...a, c=2, d=3)
# Now get a list back
echo ____
echo array @f(5, 6, ...a, c=7, d=8; ...n)