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digitalmars.D.learn - What's the rationale for considering "0x1.max" as invalid ?

reply Basile B. <b2.temp gmx.com> writes:
0x1.max // exponent expected in hex float
0x1 .max // OK
1.max // OK

What's the ambiguity when it's an hex literal ?
Apr 05 2016
next sibling parent Basile B. <b2.temp gmx.com> writes:
On Tuesday, 5 April 2016 at 19:00:43 UTC, Basile B. wrote:
 0x1.max // exponent expected in hex float
 0x1 .max // OK
 1.max // OK

 What's the ambiguity when it's an hex literal ?
https://issues.dlang.org/show_bug.cgi?id=15880
Apr 05 2016
prev sibling parent reply Alex Parrill <initrd.gz gmail.com> writes:
On Tuesday, 5 April 2016 at 19:00:43 UTC, Basile B. wrote:
 0x1.max // exponent expected in hex float
 0x1 .max // OK
 1.max // OK

 What's the ambiguity when it's an hex literal ?
It's potentially ambiguous with hexadecimal floating point numbers 0xdeadbeef.p5 // hex float or hex int + method? dlang.org/spec/lex.html#HexFloat
Apr 05 2016
parent reply Basile B. <b2.temp gmx.com> writes:
On Tuesday, 5 April 2016 at 20:56:54 UTC, Alex Parrill wrote:
 On Tuesday, 5 April 2016 at 19:00:43 UTC, Basile B. wrote:
 0x1.max // exponent expected in hex float
 0x1 .max // OK
 1.max // OK

 What's the ambiguity when it's an hex literal ?
It's potentially ambiguous with hexadecimal floating point numbers 0xdeadbeef.p5 // hex float or hex int + method? dlang.org/spec/lex.html#HexFloat
Yes but it's pointless to allow the decimal separator to be followed by the exponent: void main() { import std.stdio; writeln( typeof(0x1p5).stringof ); // double writeln( typeof(0x1.p5).stringof ); // double }
Apr 05 2016
parent reply Basile B. <b2.temp gmx.com> writes:
On Tuesday, 5 April 2016 at 21:10:47 UTC, Basile B. wrote:
 On Tuesday, 5 April 2016 at 20:56:54 UTC, Alex Parrill wrote:
 On Tuesday, 5 April 2016 at 19:00:43 UTC, Basile B. wrote:
 0x1.max // exponent expected in hex float
 0x1 .max // OK
 1.max // OK

 What's the ambiguity when it's an hex literal ?
It's potentially ambiguous with hexadecimal floating point numbers 0xdeadbeef.p5 // hex float or hex int + method? dlang.org/spec/lex.html#HexFloat
Yes but it's pointless to allow the decimal separator to be followed by the exponent: void main() { import std.stdio; writeln( typeof(0x1p5).stringof ); // double writeln( typeof(0x1.p5).stringof ); // double }
I mean that the rule could be: the decimal separator must be followed by a second group of digits. The second group of digits must be followed by an exponent. The first group of digits can be followed by an exponent. 0x1.0p5 // valid 0xp5 // valid 0x1.p5 // invalid (p is not a hex digit) 0x1.ap5 // valid
Apr 05 2016
parent Alex Parrill <initrd.gz gmail.com> writes:
On Tuesday, 5 April 2016 at 21:40:59 UTC, Basile B. wrote:
 On Tuesday, 5 April 2016 at 21:10:47 UTC, Basile B. wrote:
 On Tuesday, 5 April 2016 at 20:56:54 UTC, Alex Parrill wrote:
 On Tuesday, 5 April 2016 at 19:00:43 UTC, Basile B. wrote:
 0x1.max // exponent expected in hex float
 0x1 .max // OK
 1.max // OK

 What's the ambiguity when it's an hex literal ?
It's potentially ambiguous with hexadecimal floating point numbers 0xdeadbeef.p5 // hex float or hex int + method? dlang.org/spec/lex.html#HexFloat
Yes but it's pointless to allow the decimal separator to be followed by the exponent: void main() { import std.stdio; writeln( typeof(0x1p5).stringof ); // double writeln( typeof(0x1.p5).stringof ); // double }
I mean that the rule could be: the decimal separator must be followed by a second group of digits. The second group of digits must be followed by an exponent. The first group of digits can be followed by an exponent. 0x1.0p5 // valid 0xp5 // valid 0x1.p5 // invalid (p is not a hex digit) 0x1.ap5 // valid
Looks like that's how it works for decimal floats; I.e. 1.e5 is an int and property lookup, while 1.0e5 is 100000f. Curiously, 1. Is 1.0. I agree that floats should be parsed consistently. For now, you can do (0x1).max or typeof(0x1).max.
Apr 06 2016