On Mon, 28 Feb 2000, Dan Ingalls wrote:
who of you really would expect that 16r1e5 equals 1048576 while 16r1E5 is 485? If not too many, I propose to make hex numbers case independent, and exponent notation, too.
I have a problem with this, Bert. The way it is, there is a simple syntactic rule for numbers. Your changes imply a rule that is not syntactic, but value-dependent:
16r1E5 = 485, but 14r1E5 = 537824
I know. But the current solution is value-dependent, too. 14r1E5, according to syntactic rules, is a number. But if parsed, it is a message send with selector #E5 to the number 14r1. (I'm referring to http://minnow.cc.gatech.edu/squeak/SqueakLanguageDefinition).
I just keep running into case problems because I usually use lower case letters in hex numbers. It took me ten minutes to find out why the html color code "#00ee00" was not green.
What if we define that the exponent notation is only valid if the base is <= 10? It's a semantic, value dependant rule, more flexible, but IMHO not more ambiguous than the current one. Exponent notation is only currently used for base 10 floats and base 2 integers, so we wouldn't break anything.
The current definition for number is --------old-------- number = [radix "r"]["-"]digits["." digits]["e"["-"]exponent].
NOTE: the set of digits allowed in a number of radix N is the first N characters of the string '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'; default radix = 10, for all others you must explicitly specify the radix;
digit = decimal_digit | uppercase. --------old--------
This could be changed to:
--------new-------- number = [radix ("R"|"r")]["-"]digits["." digits][("E"|"e")["-"]exponent].
NOTE: the set of digits allowed in a number of radix N is the first N characters of the string '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ' in upper or lower case; the exponent notation is only allowed if radix is <= 10; default radix = 10, for all others you must explicitly specify the radix;
digit = decimal_digit | letter. --------new--------
What does the ANSI standard say? I guess it's the "old" definition. But even then, if exporting to the Smalltalk interchange format, literals could be brought into the canonical form.
-Bert-