Speedcrunch unsigned multiplication3/28/2023 ![]() When adding, multiplying, or otherwise manipulating units, SpeedCrunch will track the dimension and raise an error if it detects an invalid operation. Indeed, the dimension of second is time, while meter denotes a length, thus they cannot be compared, added, etc. Simply put, it prevents comparing apples and pears: If you try to convert seconds to meters, SpeedCrunch will complain, stating that the dimensions of second and meter do not match. The order explicit by using newton / (centi meter).įor the same reasons, expressions like 500 gram / 20 gram and (500 gram) / (20 gram) yield different results.Īn important feature of SpeedCrunch’s unit system is dimensional checking. ‘newtons per centimeter’, don’t simply type newton / centi meter – this will be interpreted as (newton / centi) meter! Instead, make For instance, if you intend to express the unit Means that their use follows the same rules of precedence as any other mathematical operation. This limitation (or feature, depending on your point of view) In SpeedCrunch (unlike in textbook notation), prefixes can be used on their own. In that case, the imaginary part of these numbers is discarded when passing them as an argument to a built-in function. However, previously stored variables may still contain complex values. When complex numbers are disabled, the constant j is not available. However, when given a real argument, cbrt() will always return the real cubic root, regardless of whether or not complex numbers are enabled. With complex number support enabled, the power operation x^(1/3) will return the first complex cubic root of x which is usually non-real. Refer to a function’s documentation for more information.Ĭaution is advised when using functions like cbrt() or any fractional power operation with complex numbers. ![]() Not every function in SpeedCrunch supports complex arguments. Simply defining i=j allows you to use i as an alias for j. Although SpeedCrunch does not support this notation by default, it is added easily enough. Some users (especially mathematicians or physicists) may prefer to use the letter i for the imaginary unit. If necessary, consider writing the multiplication explicitly, i.e. so you can't easily use non-widening imul if you want to detect when the full unsigned result didn't fit.J ^ 2 = -1 ( 5 + 3 j ) / ( 8 - 2 j ) = 0.5+0.5jĪ note on the syntax of complex numbers: 5j denotes the number 5*j while j5 is a variable named ‘j5’. (Or if you want FLAGS set according to unsigned overflow of the low half, instead of signed overflow. Only widening multiply needs a separate form. The low half of signed and unsigned multiply is the same, that's why x86 for example only has immediate and 2-operand forms of imul, not also mul. Widening signed-multiply doesn't involve any truncation. ![]() Or for another example, see Why are signed and unsigned multiplication different instructions on x86(-64)? But the full signed result is not always the operand-size truncation of the unsigned product.įor example, -128 * 127 is -16256, or as 16-bit 2's complement, 0xc080.īut 0x80 * 0x7f is + 16256, i.e. (249-256) * (243-256) = 0x005b, a small positive result that happens to fit in the low half of the full result. I think your choice of example misled you into thinking the signed product could be obtained by truncating the 8x8 => 16-bit unsigned product down to 8 bits.
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