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- Default value
- Binary encoding of real numbers
- Thousand separator
- Precision issues with reals
- PHP-specific features
- Differences with WINDEV/WEBDEV 5.5
Real (Variable type) In french: Real
The Real type allows you to perform calculations on real values using up to 15 significant digits. This type might suffer from loss of precision. For accurate calculations, use " Currency". Syntax
<Variable name> is real
<Variable name 1>, <Variable name 2> are reals
<Variable name>: Name of the variable to declare. This variable will be an 8-byte real. A real can contain up to 15 significant digits. The value of a real corresponds to:- Minimum value:1.7*10-308
- Maximum value: 1.7*10+308
<Variable name> is 4-byte real
<Variable name 1>, <Variable name 2> are 4-byte reals
<Variable name>: Name of the variable to declare. This variable will be a 4-byte real. A 4-byte real can contain up to 6 significant digits.
The value of a 4-byte real corresponds to:- Minimum value: 3.4*10-38
- Maximum value: 3.4*10+38
Remarks Default value A "Real" variable that is declared but not initialized is equal to 0. Binary encoding of real numbers All the reals contain the same number of significant digits (15). If the result of a calculation performed on reals involves more than 15 significant digits, this result will be automatically rounded to 15 significant digits. For a better precision, use the Currency or Numeric type. Thousand separator You can use spaces and underscore characters to separate thousands in numbers. For example: num1 is real
num1 = 123 456.478
num2 is real
num2 = 7_014.478
Precision issues with reals Operations with the "Real" type are not precise because of the computer representation of real numbers. Two reals that are equal mathematically speaking are not necessarily equal computer-wise and the ">", "<" or "=" operators can return results that are "false" mathematically speaking. To solve some of these problems: - the "=" operator achieves a precision of 10e-6 on reals. Therefore, for two reals that are relatively close, the "=" and ">" operators (or "=" and "<") can return True for the same values.
- the conversion of real values to strings uses a complex algorithm. This is why, in most cases, the data displayed in the trace is correct.
To avoid these problems, use the Currency or Numeric type, which uses an exact memory representation.
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