Hi Christophe, > That the results are analog, but different. To obtain exactly the same > results that pil32, > I had to write: > > seed () > long n = (Seed = initSeed(ex.Cdr.Car.eval()) * 6364136223846793005L) >>> > 32; > return new Number(n%2==0 ? n/2 : -(n-1)/2);
Is it really so important that the random generators give the same results? I had never intended that. The reason is that the random generator should be as simple (fast) as possible, and all four implementations represent numbers differently: 1. pil32 has only bignums, where the random generator restricts itself to a single cell. Each bignum cell can hold 32 bits, where the sign bit is in bit 0 (no two's complement!). Therefore, the value is multiplied by 2, and the sign bit is added. 2. pil64 has bignums with 64 bits in each cell, and short numbers with 60 bits plus a sign bit in bit 3 (bits 0 - 2 are tag bits). Random numbers are placed into short numbers. 3. miniPicoLisp has only short numbers (in two's complement, either 30 bit on 32-bit machines, or 62 bits on 64-bit machines including the sign). 4. Ersatz uses BigIntegers for bignums, and 'int's for short numbers. Thus, a random number is a two's complement 32-bit integer. So there is no "natural" way to get completely equal results. ♪♫ Alex -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
