Rounding using .ceil only checks the first decimal

[andydolan94]

I'm currently attempting to use the rounding methods from this library and I'm finding that the ceil function doesn't provide the desired output

Expected Behavior

const numberToRound = new Decimal128(100.05);
console.log(numberToRound.round(0, "floor").toNumber());
// outputs 100
console.log(numberToRound.round(0, "ceil").toNumber());
// outputs 101

Current Behavior

const numberToRound = new Decimal128(100.05);
console.log(numberToRound.round(0, "floor").toNumber());
// outputs 100
console.log(numberToRound.round(0, "ceil").toNumber());
// outputs 100 - incorrect

Context (Environment)

Using the latest version of Decimal128 17.0.0 on Deno 1.46.3

[jessealama]

Can you try using "100.05" rather than 100.05? I suspect the difficulty is that 100.05 (without the quotes) is getting rounded rather badly.

[jessealama]

You might be interested to know that 100.05 is one of those "wicked" values that leads to trouble. See the discussion in the decimal proposal repo.

[jessealama]

Can you try this again with "100.05", in quotes, rather than 100.05?

[amoshydra]

This is reproducible when the input is a string:
https://codepen.io/amoshydra/pen/NPKXrGB?editors=0010

The output below round using "ceil" rounding mode

current:

"100.1" rounding to 0 decimals = "101"
"100.05" rounding to 0 decimals = "100"
"100.05" rounding to 1 decimals = "100.1"
"100.005" rounding to 1 decimals = "100"

expected:

"100.1" rounding to 0 decimals = "101"
"100.05" rounding to 0 decimals = "101"
"100.05" rounding to 1 decimals = "100.1"
"100.005" rounding to 1 decimals = "100.1"

[amoshydra]

I have added more tests for round and precision at #128. It is currently still in draft. But we should be able to verify the correctness of the tests first.

In the PR I have found the following unexpected cases for .round for the various rounding mode

rounding non-decimal > mode: floor > -1 round(0) to be -1
    
    Expected: "-1"
    Received: "-2"

rounding non-decimal > mode: floor > -1 round(1) to be -1
    
    Expected: "-1"
    Received: "-1.1"

rounding non-decimal > mode: floor > -1 round(10) to be -1
    
    Expected: "-1"
    Received: "-1.0000000001"

rounding non-decimal > mode: floor > -1.11e+10 round(0) to be -11100000000
    
    Expected: "-11100000000"
    Received: "-11100000001"

rounding non-decimal > mode: floor > -1.11e+10 round(1) to be -11100000000
    
    Expected: "-11100000000"
    Received: "-11100000000.1"

rounding non-decimal > mode: floor > -1.11e+10 round(10) to be -11100000000
    
    Expected: "-11100000000"
    Received: "-11100000000.0000000001"

rounding non-decimal > mode: floor > -0.011e+10 round(0) to be -110000000
    
    Expected: "-110000000"
    Received: "-110000001"

rounding non-decimal > mode: floor > -0.011e+10 round(1) to be -110000000
    
    Expected: "-110000000"
    Received: "-110000000.1"

rounding non-decimal > mode: floor > -0.011e+10 round(10) to be -110000000
    
    Expected: "-110000000"
    Received: "-110000000.0000000001"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -0.5 round(1) to be -0.5
    
    Expected: "-0.5"
    Received: "-0.6"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -1.5 round(1) to be -1.5
    
    Expected: "-1.5"
    Received: "-1.6"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -0.15 round(2) to be -0.15
    
    Expected: "-0.15"
    Received: "-0.16"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -1.15 round(2) to be -1.15
    
    Expected: "-1.15"
    Received: "-1.16"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -0.1000000000000000000000000000000015 round(34) to be -0.1000000000000000000000000000000015
    
    Expected: "-0.1000000000000000000000000000000015"
    Received: "-0.1000000000000000000000000000000016"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -0.100000000000000000000000000000001 round(34) to be -0.100000000000000000000000000000001
    
    Expected: "-0.100000000000000000000000000000001"
    Received: "-0.1000000000000000000000000000000011"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -1.000000000000000000000000000000015 round(33) to be -1.000000000000000000000000000000015
    
    Expected: "-1.000000000000000000000000000000015"
    Received: "-1.000000000000000000000000000000016"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -1.00000000000000000000000000000001 round(33) to be -1.00000000000000000000000000000001
    
    Expected: "-1.00000000000000000000000000000001"
    Received: "-1.000000000000000000000000000000011"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -0.100000000000000015 round(34) to be -0.100000000000000015
    
    Expected: "-0.100000000000000015"
    Received: "-0.1000000000000000150000000000000001"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -0.10000000000000001 round(34) to be -0.10000000000000001
    
    Expected: "-0.10000000000000001"
    Received: "-0.1000000000000000100000000000000001"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -1.00000000000000015 round(33) to be -1.00000000000000015
    
    Expected: "-1.00000000000000015"
    Received: "-1.000000000000000150000000000000001"

rounding decimals > unnecessary rounding should return the same output as the input > mode: floor > -1.0000000000000001 round(33) to be -1.0000000000000001
    
    Expected: "-1.0000000000000001"
    Received: "-1.000000000000000100000000000000001"

rounding decimals > "Symbol(NoExplicitMode)" > rounding decimal to integer > input: "-0.6" > decimals: "0" > output: "-1"
    
    Expected: "-1"
    Received: "1"

rounding decimals > "Symbol(NoExplicitMode)" > rounding decimal (1) > input: "-0.06" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "0.1"

rounding decimals > "ceil" > rounding decimal to integer > input: "-0.4" > decimals: "0" > output: "-0"
    
    Expected: "-0"
    Received: "1"

rounding decimals > "ceil" > rounding decimal to integer > input: "-0.5" > decimals: "0" > output: "-0"
    
    Expected: "-0"
    Received: "1"

rounding decimals > "ceil" > rounding decimal to integer > input: "-0.6" > decimals: "0" > output: "-0"
    
    Expected: "-0"
    Received: "1"

rounding decimals > "ceil" > rounding decimal (1) > input: "-0.04" > decimals: "1" > output: "-0"
    
    Expected: "-0"
    Received: "0.1"

rounding decimals > "ceil" > rounding decimal (1) > input: "-0.05" > decimals: "1" > output: "-0"
    
    Expected: "-0"
    Received: "0.1"

rounding decimals > "ceil" > rounding decimal (1) > input: "-0.06" > decimals: "1" > output: "-0"
    
    Expected: "-0"
    Received: "0.1"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "0.0004" > decimals: "1" > output: "0.1"
    
    Expected: "0.1"
    Received: "0"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "0.0005" > decimals: "1" > output: "0.1"
    
    Expected: "0.1"
    Received: "0"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "0.0006" > decimals: "1" > output: "0.1"
    
    Expected: "0.1"
    Received: "0"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "0.0004" > decimals: "2" > output: "0.01"
    
    Expected: "0.01"
    Received: "0"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "0.0005" > decimals: "2" > output: "0.01"
    
    Expected: "0.01"
    Received: "0"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "0.0006" > decimals: "2" > output: "0.01"
    
    Expected: "0.01"
    Received: "0"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "5.0004" > decimals: "1" > output: "5.1"
    
    Expected: "5.1"
    Received: "5"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "5.0005" > decimals: "1" > output: "5.1"
    
    Expected: "5.1"
    Received: "5"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "5.0006" > decimals: "1" > output: "5.1"
    
    Expected: "5.1"
    Received: "5"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "5.0004" > decimals: "2" > output: "5.01"
    
    Expected: "5.01"
    Received: "5"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "5.0005" > decimals: "2" > output: "5.01"
    
    Expected: "5.01"
    Received: "5"

rounding decimals > "ceil" > rounding decimal (1) on number with much higher (> 2) precision > input: "5.0006" > decimals: "2" > output: "5.01"
    
    Expected: "5.01"
    Received: "5"

rounding decimals > "floor" > rounding decimal to integer > input: "-0.4" > decimals: "0" > output: "-1"
    
    Expected: "-1"
    Received: "-0"

rounding decimals > "floor" > rounding decimal to integer > input: "-0.5" > decimals: "0" > output: "-1"
    
    Expected: "-1"
    Received: "-0"

rounding decimals > "floor" > rounding decimal to integer > input: "-0.6" > decimals: "0" > output: "-1"
    
    Expected: "-1"
    Received: "-0"

rounding decimals > "floor" > rounding decimal (1) > input: "-0.04" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "-0"

rounding decimals > "floor" > rounding decimal (1) > input: "-0.05" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "-0"

rounding decimals > "floor" > rounding decimal (1) > input: "-0.06" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "-0"

rounding decimals > "floor" > rounding decimal (1) on number with much higher (> 2) precision > input: "-0.0004" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "-0"

rounding decimals > "floor" > rounding decimal (1) on number with much higher (> 2) precision > input: "-0.0005" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "-0"

rounding decimals > "floor" > rounding decimal (1) on number with much higher (> 2) precision > input: "-0.0006" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "-0"

rounding decimals > "floor" > rounding decimal (1) on number with much higher (> 2) precision > input: "-0.0004" > decimals: "2" > output: "-0.01"
    
    Expected: "-0.01"
    Received: "-0"

rounding decimals > "floor" > rounding decimal (1) on number with much higher (> 2) precision > input: "-0.0005" > decimals: "2" > output: "-0.01"
    
    Expected: "-0.01"
    Received: "-0"

rounding decimals > "floor" > rounding decimal (1) on number with much higher (> 2) precision > input: "-0.0006" > decimals: "2" > output: "-0.01"
    
    Expected: "-0.01"
    Received: "-0"

rounding decimals > "halfExpand" > rounding decimal to integer > input: "-0.5" > decimals: "0" > output: "-1"
    
    Expected: "-1"
    Received: "1"

rounding decimals > "halfExpand" > rounding decimal to integer > input: "-0.6" > decimals: "0" > output: "-1"
    
    Expected: "-1"
    Received: "1"

rounding decimals > "halfExpand" > rounding decimal (1) > input: "-0.05" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "0.1"

rounding decimals > "halfExpand" > rounding decimal (1) > input: "-0.06" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "0.1"

rounding decimals > "halfEven" > rounding decimal to integer > input: "-0.6" > decimals: "0" > output: "-1"
    
    Expected: "-1"
    Received: "1"

rounding decimals > "halfEven" > rounding decimal (1) > input: "-0.06" > decimals: "1" > output: "-0.1"
    
    Expected: "-0.1"
    Received: "0.1"