Allow integer seeds.

Author: mbostock

README.md

@@ -117,4 +117,4 @@ random(); // -0.6253955998897069
 
 <a name="randomLcg" href="#randomLcg">#</a> d3.<b>randomLcg</b>([<i>seed</i>]) · [Source](https://github.com/d3/d3-random/blob/master/src/lcg.js), [Examples](https://observablehq.com/@d3/d3-randomlcg)
 
-Returns a [linear congruential generator](https://en.wikipedia.org/wiki/Linear_congruential_generator); this function can be called repeatedly to obtain pseudorandom values well-distributed on the interval [0,1) and with a long period (up to 1 billion numbers), similar to Math.random. A *seed* can be specified as a number in the interval [0,1). Two generators instanced with the same seed generate the same sequence, allowing to create reproducible pseudo-random experiments. If the *seed* is not specified, one is chosen using Math.random.
+Returns a [linear congruential generator](https://en.wikipedia.org/wiki/Linear_congruential_generator); this function can be called repeatedly to obtain pseudorandom values well-distributed on the interval [0,1) and with a long period (up to 1 billion numbers), similar to Math.random. A *seed* can be specified as a real number in the interval [0,1) or as any integer. In the latter case, only the lower 32 bits are considered. Two generators instanced with the same seed generate the same sequence, allowing to create reproducible pseudo-random experiments. If the *seed* is not specified, one is chosen using Math.random.

src/lcg.js

@@ -1,10 +1,9 @@
 // https://en.wikipedia.org/wiki/Linear_congruential_generator#Parameters_in_common_use
 const mul = 0x19660D;
 const inc = 0x3C6EF35F;
-const eps = 1/0x100000000;
+const eps = 1 / 0x100000000;
 
 export default function lcg(seed = Math.random()) {
-  if (!(0 <= seed && seed < 1)) throw new RangeError("invalid seed");
-  let state = seed / eps | 0;
+  let state = (0 <= seed && seed < 1 ? seed / eps : Math.abs(seed)) | 0;
   return () => (state = mul * state + inc | 0, eps * (state >>> 0));
 }