Question

I was writing a small console application in Delphi (XE), and by mistake wrote:

for I := 0to aList.Count-1 do 

Note the missing space between “0” and “to”

I didn’t notice this until after I had run the program, and I was surprised the compiler accepted this. It’s probably no big deal, but it made me curious.

Why does Delphi accept this typo?

Answer 1

It’s for the same reason that you don’t need spaces around the . or the -. Since a t can never come after an initial 0 in any recognisable token, the lexical analyser simply returns the 0 as an integer-literal token, and then recognises the to as a distinct keyword token. If you had made a different mistake instead — for I := 0 to10 — you’d now have a problem, since to10 is recognised as a valid identifier, which is illegal immediately after the 0.