CODEWITHSUNDEEP
javascriptboolean
Musixauce3000
Musixauce3000

Reputation: 559

Why does the statement `0 < 0.5 < 1` reduce to false?

I recently discovered the ECMAScript Spec, which I was able to use to answer a question I've had about Math.random() for a while; namely whether or not it would ever generate 0 without the help of Math.floor().

The ECMAScript Spec specifies that 0 <= Math.random() < 1, unlike literally anyone else for some reason. I hopped over to the console and ran a test before saving it in my notes but noticed that statement reduces to false.

Below is a function that tests everything about comparison statements that I thought might be causing this lie. I call the function twice to generate two arrays of Boolean values, and the results seem to imply that literally this statement: 0 <= Math.random() < 1 - and this statement alone, returns FALSE where it should return TRUE. Especially when you consider bonus round where I test the exact same statement but with an additional comparison tacked onto the end, and it also returns true

function getTruths( a, b, c ) {
  
  return [
    
    a + 1 < b + 1,
    a + 1 < c + 1,
    b + 1 < c + 1,
    a + 1 < b + 1 < c + 1,
    
    a + 0 < b + 0,
    a + 0 < c + 0,
    b + 0 < c + 0,
    a + 0 < b + 0 < c + 0
    
  ];
  
}

function demonstrate() {
  
  // array of truth
  console.log( getTruths( 0, 1, 2 ) );
  
  // array of lies
  console.log( getTruths( 0, 0.5, 1 ) );
  
  // bonus round
  return [ 0 < 0.5 < 1 < 1.5 ];
  
}

demonstrate();

So I did some more plucking around and learned that it isn't just that. it seems that a and b can actually be any value lower that one and equal to or greater than zero, just as long as b is still bigger than a, and c is still equal to 1 of course... and given those parameters, no matter what, the return is still FALSE. If you add 1 to everything though suddenly you're in good shape again, just as in the function provided above.

Anyway can someone explain this to me? Thanks.

Upvotes: 0

Views: 167

Answers (1)

Pointy
Pointy

Reputation: 413737

a < b < c

is interpreted as

(a < b) < c

The result value from a relational operator like < is a boolean, either true or false. If c is a number, then, that boolean will be converted to a number, either 1 (true) or 0 (false). Thus c is compared to either 0 or 1, not the values of either a or b.

The proper way to write "is b strictly between a and c" is

a < b && b < c

Upvotes: 4

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