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Command vs. Expression Mode

Table of Contents
From Command Mode to Expression Mode
From Expression Mode to Command Mode
Does that mean that functions arguments can’t be globs?

Here is a list of places we switch modes:

From Command Mode to Expression Mode


var x = 1 + f(x)    # RHS of var/setvar
setvar x = 1 + f(x)
setvar x = obj.method()   

x = 1 + f(x)   # when parse_equals is on, = becomes special

do parses in expression mode, and throws away the return value:

do 1 + f(x)
do obj.method()

Arguments to Inline function calls:

echo $strfunc(x, y + f(z))
echo @arrayfunc(x, y + f(z))

Parameter Lists

func add(x = 5, y = 2) {  # what's between () is in expression mode
  return x + y   # this part is in command mode

Oil if/while/for

if (x > 0) { ... }
while (x > 0) { ... }
for (x, y in pairs) { ... }

From Expression Mode to Command Mode

var x = func(x) { echo hi; return x +1 }   # everything between {} is in command mode


Braced Vars in Double Quotes:

echo ${f(x)}

This is an incomplete list. Double quoted strings are yet another lexer mode I didn't list.

Does that mean that functions arguments can’t be globs?

For example:


Good question, yes in expressions globs have to be quoted:


ls *.py
echo $myfunc('*.py')
if (x ~ '*.py') {  # ~ operator also matches globs, not implemented yet
  echo yes


echo '*.py'  # not a glob
echo $myfunc(*.py)  # syntax error

So yeah you do have to have an awareness of what's an expression and what's a "word/command", which is why I highlighted it.

Right I should have clarified – they don’t turn globbing back on. It’s just a string. It’s up to the function that is called to interpret as a glob or not.

It’s exactly like the difference between:

from glob import glob; glob('*.py')  # yes glob
os.listdir('*.py')  # no glob because it's not how listdir() works

in Python. Single quoted strings in Oil are just like string literals in Python. Does that make sense?

I’m not sure what you mean by myEcho? Both of these work in Oil just like they do in sh:

echo *
echo '*'

Because you’ve never entered expression mode. You’re still in command mode.

Generated on Sun Jan 19 22:59:37 PST 2020