when I'm converting string '-0'in float it returns float type -0
example
$x = '-0';
$y = (float)$x;
result => float -0
why -0 is float number ?
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Anri
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You are explicitly casting it to `(float)`, are you not? – Sergiu Paraschiv Aug 12 '14 at 08:15
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in my mind -0 can not be float value ... – Anri Aug 12 '14 at 08:16
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you are casting it to float. and asking why it is float now. – Satish Sharma Aug 12 '14 at 08:16
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2*Why* can it not be a float value? – deceze Aug 12 '14 at 08:18
2 Answers
5
The IEEE 754 standard, which is how almost all computer languages implement floating point numbers, has both a +0 and a -0 value.
For most operations, +0 and -0 can be used interchangeably.
However, operations that error out to infinity, use +0 or -0 to go to +Infinity and -Infinity.
Because -0 is a valid floating point number, it makes perfect sense that casting -0 to a float would do exactly as you asked --- returning a floating point number with a value of exactly -0.
Jeremy J Starcher
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what is different between -0 and +0 ? what will output if(-0 == +0) TRUE or FALSE ? – Anri Aug 12 '14 at 08:19
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2@Anri - 30 seconds with PHP would answer that question faster than it takes to ask it here. – Jeremy J Starcher Aug 12 '14 at 08:21
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They are equal. "PHP typically uses the IEEE 754 double precision format" - Read this thread: http://stackoverflow.com/questions/5095968/does-float-have-a-negative-zero-0f – Sergiu Paraschiv Aug 12 '14 at 08:21
