no ambiguity in assignments

[flying-sheep]

Some parsing ambiguities are resolved by considering whitespace around operators. See and despair: x<-y (assignment) is parsed differently than x < -y (comparison)!

but that’s not ambiguous. <- is simply a symbol, so if it occurs together, it’s always the assignment operator. (afaik)

[Protonk]

The ambiguity stems from the somewhat leaky convention that whitespace isn't significant. In this case, whitespace is not significant until it is interposed between two characters which comprise a single symbol.

[flying-sheep]

but identifiers are also single symbols separated by whitespace, and are like this in most programming languages that are considered without significant whitespace. so are keywords: else if≠ elseif

[kevinushey]

The point is, novice R programmers might write something like

x=1;
y=2;
if(y<-x) print(1) else print(2) ## what? y isn't less than negative x, why do we print 1?

It's ambiguous in that there are two possible ways to parse y<-x, but the parser chooses the '<- is a symbol' case (rightly so). A novice R programmer who doesn't realize <- is used for assignment and hates whitespace would run into surprises like this.

[flying-sheep]

You’re right. Could be a bit clearer on the page, but now i got it :)