I would argue that this is a matter of preference and the arguments on "principle" for one side or another are not particularly compelling. When the "=" was introduced for assignment, an argument was made that name=value function arguments are also implicitly a kind of assignment. While Duncan has pointed out a typical example of how this could be ambiguous, <- also has its problems. A syntactic confusion with "<-" arises in expressions like x<-3 which could be read either as an assignment or as a logical expression comparing x to -3. Perhaps obviously ambiguous when written naked like this but when buried in a larger expression, it's easy to write an expression like that and discover that you have overwritten x. Some might (and have, most emphatically) advise that we should routinely insert spaces in our typing in a way that disambiguates such expressions but I find an argument that relies on spaces, which are usually syntactically unmeaningful, not very compelling. Besides, I just find that clumsy two-character arrow ugly! This is an esthetic matter -- reminds me too much of an emoticon. :-( For over 10 years I used the alternative "_" underscore for S assignment (nice as a single character with no competing syntactic meaning) but that has gone away, as far as I can tell primarily due to discomfort (disdain?) of developers who find it unattractive because of the use of "_" as a connecting special category in OTHER contexts (C and shell programming). However, a mutually satisfactory solution is at hand!! If growth in the number of R programmers continues exponentially at its current rate, by the year 2097 the number of R programmers will exceed the population of the earth. At that point they will rise up and demand the restoration of the APL arrow key (remembered by some doddering guru who heard about it from her grandfather) to the standard keyboard, and our problem will be solved. (But there will be a minor irritation because in the New Zealand keyboard that key code will have been assigned to the locally popular sheep icon.) Alan Zaslavsky
Is there any difference between <- and =
3 messages · Alan Zaslavsky, Wacek Kusnierczyk
Alan Zaslavsky wrote:
I would argue that this is a matter of preference and the arguments on "principle" for one side or another are not particularly compelling.
indeed; i have argued (i think...) for treating them as equals, the vhoice being a matter of taste.
When the "=" was introduced for assignment, an argument was made that name=value function arguments are also implicitly a kind of assignment.
sure they are. you assign (or not, depending on whether the arguments are actually used) to function-call-local variables, that is, the function's parameters.
While Duncan has pointed out a typical example of how this could be
ambiguous, <- also has its problems. A syntactic confusion with "<-"
arises in expressions like
x<-3
which could be read either as an assignment or as a logical expression
comparing x to -3.
ha! cool.
Perhaps obviously ambiguous when written naked like this but when buried in a larger expression, it's easy to write an expression like that and discover that you have overwritten x.
even worse if the code is processed in some way that might remove spaces, thus turning < - into <-.
Some might (and have, most emphatically) advise that we should routinely insert spaces in our typing in a way that disambiguates such expressions but I find an argument that relies on spaces, which are usually syntactically unmeaningful, not very compelling. Besides, I just find that clumsy two-character arrow ugly!
:)
This is an esthetic matter -- reminds me too much of an emoticon. :-( For over 10 years I used the alternative "_" underscore for S assignment (nice as a single character with no competing syntactic meaning) but that has gone away, as far as I can tell primarily due to discomfort (disdain?) of developers who find it unattractive because of the use of "_" as a connecting special category in OTHER contexts (C and shell programming). However, a mutually satisfactory solution is at hand!! If growth in the number of R programmers continues exponentially at its current rate, by the year 2097 the number of R programmers will exceed the population of the earth. At that point they will rise up and demand the restoration of the APL arrow key (remembered by some doddering guru who heard about it from her grandfather) to the standard keyboard, and our problem will be solved. (But there will be a minor irritation because in the New Zealand keyboard that key code will have been assigned to the locally popular sheep icon.)
by that time r programs will be scanned directly from your head, i suppose, and the intelligent scanner will as gladly take <- as it will =, so the problem will rather vanish. vQ
thanks for your supportive comments! by that time r programs will be scanned directly from your head, i suppose, and the intelligent scanner will as gladly take <- as it will =, so the problem will rather vanish. Yes, and maybe the scanner will be more intelligent than the programmer so when the programmer is confused about what he/she wants, the scanner will figure it out! :-)