Roku Developer Program

[daleus]

I made a sandbox app to test simple pieces of code and I found out something interesting about string concatenation. I'm curious as to why it's implemented in this way.

The code:

sub RunUserInterface()

	mainScreen	= CreateObject("roPosterScreen")
	msgPort	= CreateObject("roMessagePort")
	mainScreen.SetMessagePort(msgPort)
	
	adjective = "funny"
	mainScreen.ShowMessage("this is a "+adjective+" test")          ' *** concatenation works correctly
	print "this is a "+adjective+" test"                            ' *** concatenation works correctly

	mainScreen.Show()

	while true
		msg = Wait(0, mainScreen.GetMessagePort())
		
		if type(msg) = "roPosterScreenEvent"
			if msg.isScreenClosed()
				exit while
			end if
		end if
	end while
	
	mainScreen.Close()

end sub

You can see that both the ShowMessage() function and the print statement uses a plus (+) sign to concatenation strings. I am able to change the code so that the print statement uses a semi-colon (;) instead, but if I also try that on the ShowMessage() function, I get a syntax error.

sub RunUserInterface()

	mainScreen	= CreateObject("roPosterScreen")
	msgPort	= CreateObject("roMessagePort")
	mainScreen.SetMessagePort(msgPort)
	
	adjective = "funny"
	mainScreen.ShowMessage("this is a ";adjective;" test")          ' *** concatenation does not work (syntax error)
	print "this is a ";adjective;" test"                            ' *** concatenation works correctly

	mainScreen.Show()

	while true
		msg = Wait(0, mainScreen.GetMessagePort())
		
		if type(msg) = "roPosterScreenEvent"
			if msg.isScreenClosed()
				exit while
			end if
		end if
	end while
	
	mainScreen.Close()

end sub

[RokuJoel]

Print has features that let you format your output. Showmessage does not, so with Showmessage, you have to have create a string and pass it to the show message function like myposterscreen.ShowMessage("This is a "+chr(34)+" quote character")

- Joel

[daleus]

Oh, I see.

Thanks for clearing that up.

[EnTerr]

"daleus" wrote:
You can see that both the ShowMessage() function and the print statement uses a plus (+) sign to concatenation strings. I am able to change the code so that the print statement uses a semi-colon (;) instead

"print" is a BASIC statement, not a function/procedural call with variable number of arguments and as such has somewhat free syntax. In particular, if i remember, "," separates printed arguments with extra spaces (or \t) - when ";" prints them "glued" together