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module.exports = compile;
var BaseFuncs = require("boolbase"), trueFunc = BaseFuncs.trueFunc, falseFunc = BaseFuncs.falseFunc;
/* returns a function that checks if an elements index matches the given rule highly optimized to return the fastest solution */ function compile(parsed){ var a = parsed[0], b = parsed[1] - 1;
//when b <= 0, a*n won't be possible for any matches when a < 0
//besides, the specification says that no element is matched when a and b are 0
if(b < 0 && a <= 0) return falseFunc;
//when a is in the range -1..1, it matches any element (so only b is checked)
if(a ===-1) return function(pos){ return pos <= b; }; if(a === 0) return function(pos){ return pos === b; }; //when b <= 0 and a === 1, they match any element
if(a === 1) return b < 0 ? trueFunc : function(pos){ return pos >= b; };
//when a > 0, modulo can be used to check if there is a match
var bMod = b % a; if(bMod < 0) bMod += a;
if(a > 1){ return function(pos){ return pos >= b && pos % a === bMod; }; }
a *= -1; //make `a` positive
return function(pos){ return pos <= b && pos % a === bMod; }; }
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