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spir schrieb:
On Sat, 23 Jan 2010 20:34:39 +0100 spir <denis.spir@free.fr> wrote:Hello, Is "maxInt == 1e14-1" true? (found by trying to display -- higher values get exp notation)PS: Just read at http://stackoverflow.com/questions/945731/what-is-the-maximum-value-of-a-number-in-lua that the mantissa is 52-bit wide. This should allow slightly bigger integers, no? (0xfffffffffffff ~ 4.5035996273705e+15, if I'm right)Is there any available tool for bigger (accurate) integers / for arbitrary long integers?I will need integers which width is n*24 bits, where n is not yet known, but for sure >= 3. Denis ________________________________ la vita e estrany http://spir.wikidot.com/
In lua/llimits.h you find (a code snippet): ... 00018 /* 00019 ** try to find number of bits in an integer 00020 */ 00021 #ifndef BITS_INT 00022 /* avoid overflows in comparison */ 00023 #if INT_MAX-20 < 32760 00024 #define BITS_INT 16 00025 #else 00026 #if INT_MAX > 2147483640L 00027 /* machine has at least 32 bits */ 00028 #define BITS_INT 32 00029 #else 00030 #error "you must define BITS_INT with number of bits in an integer" 00031 #endif 00032 #endif 00033 #endif ... So it is clear, that "maxInt == 1e14-1" never can be true!2^32 = 4294967296, that means you have a limit of 2147483648 in two complement representation (because of the bisectioning of the binary number circle to + and - sign) say a representation of positive numbers 0 to +2147483647 and negative numbers -1 to -2147483648, that is much smaller than the 1e14-1 you expected. From where did you get that huge number? May be you mixed up integer representation and IEEE floating point format?
May be I completely misunderstand your posting and your goal with the equality test? BTW, an equality test with other formats as integer always is eval, better use barriers.
Example:
for (i=0.0; i==1; i+=0.1) {...} - looks fine.
A float representation of 1.0 usually gives 0.99999999 in a bunary
representation and 0.999999999 == 1 ? True or false?
Regards BB