Re: Added `continue` keyword to Lua 5.4 [code review requested].
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- Subject: Re: Added `continue` keyword to Lua 5.4 [code review requested].
- From: Sean Conner <sean@...>
- Date: 2023年3月18日 04:28:04 -0400
It was thus said that the Great GoldenKnightFly once stated:
> `continue` is useful if you're working with input checking. For example
> you're checking user input through stdin, you want to check if it's valid
> if not do the input again.
>
> while true do
> io.write "Please input an ascii code: "
> local input = io.read()
>
> if not input:match "^%d+$" then
> print "Not a number"
> continue
> end
>
> local ok,ch = pcall(string.char,tonumber(input))
> if not ok and ch then
> print("Failed to parse code:",ch)
> continue
> end
>
> print("Char: "..ch)
> break
> end
> end
I get around the lack of a continue in Lua by using the fact that Lua
supports tail-call optimization. I would recode the above to be:
function foo()
io.write "Please input an ASCII code: "
local input = io.read()
if not input:match "^%d+$" then
print "Not a number"
return foo()
end
local ok,ch = pcall(string.char,tonumber(input))
if not okay and ch then
print("Failed to parse code: ",ch)
return foo()
end
print("Char: " .. ch)
end
foo()
This works across Lua versions 5.1 and higher.
-spc