Revisions to '100' is a magic number - Code Review Stack Exchange

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edited May 13, 2014 at 3:30

Jamal

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Speaking as a human programmer (i.e. I am not Lint software), your use of "100" there looks fine to me.

Wikipedia has an article (without citations) titled Accepted limited use of magic numbers: IMO your "100" is in the same category as these other "accepted" magic numbers.

This Wiki describing magic numbers says two things.

Firstly,

Practical Magic Number rule: A literal is a not a magic number if the most meaningful variable name for it is the same as the spoken name of the literal.

That's applicable here: you're looking for a named constant like HUNDREDHUNDRED or CENTUMCENTUM.

Secondly, it also suggests loading "magic" numbers (e.g. a "discount rate") from a configuration file:

static final double DISCOUNT_PERCENT = getProperty( "sales.discount_percent" );
static final double DISCOUNT_FACTOR = 1 - (DISCOUNT_PERCENT / 100);

// ...

salePrice = DISCOUNT_FACTOR * regularPrice;

Note that though this example code carefully loaded DISCOUNT_PERCENTDISCOUNT_PERCENT from a configuration, the "100" used to calculate the DISCOUNT_FACTORDISCOUNT_FACTOR is hard-coded.

If you use "100" instead of HUNDREDHUNDRED, it's easier for a programmer to understand, and to verify that it's correct.

IMO the only benefit to using HUNDREDHUNDRED is to find the several methods which use the same magic number (in your example it's used by getPercentgetPercent and getRategetRate).

Speaking as a human programmer (i.e. I am not Lint software), your use of "100" there looks fine to me.

Wikipedia has an article (without citations) titled Accepted limited use of magic numbers: IMO your "100" is in the same category as these other "accepted" magic numbers.

This Wiki describing magic numbers says two things.

Firstly,

Practical Magic Number rule: A literal is a not a magic number if the most meaningful variable name for it is the same as the spoken name of the literal.

That's applicable here: you're looking for a named constant like HUNDRED or CENTUM.

Secondly, it also suggests loading "magic" numbers (e.g. a "discount rate") from a configuration file:

static final double DISCOUNT_PERCENT = getProperty( "sales.discount_percent" );
static final double DISCOUNT_FACTOR = 1 - (DISCOUNT_PERCENT / 100);

// ...

salePrice = DISCOUNT_FACTOR * regularPrice;

Note that though this example code carefully loaded DISCOUNT_PERCENT from a configuration, the "100" used to calculate the DISCOUNT_FACTOR is hard-coded.

If you use "100" instead of HUNDRED, it's easier for a programmer to understand, and to verify that it's correct.

IMO the only benefit to using HUNDRED is to find the several methods which use the same magic number (in your example it's used by getPercent and getRate).

Speaking as a human programmer (i.e. I am not Lint software), your use of "100" there looks fine to me.

Wikipedia has an article (without citations) titled Accepted limited use of magic numbers: IMO your "100" is in the same category as these other "accepted" magic numbers.

This Wiki describing magic numbers says two things.

Firstly,

Practical Magic Number rule: A literal is a not a magic number if the most meaningful variable name for it is the same as the spoken name of the literal.

That's applicable here: you're looking for a named constant like HUNDRED or CENTUM.

Secondly, it also suggests loading "magic" numbers (e.g. a "discount rate") from a configuration file:

static final double DISCOUNT_PERCENT = getProperty( "sales.discount_percent" );
static final double DISCOUNT_FACTOR = 1 - (DISCOUNT_PERCENT / 100);

// ...

salePrice = DISCOUNT_FACTOR * regularPrice;

Note that though this example code carefully loaded DISCOUNT_PERCENT from a configuration, the "100" used to calculate the DISCOUNT_FACTOR is hard-coded.

If you use "100" instead of HUNDRED, it's easier for a programmer to understand, and to verify that it's correct.

IMO the only benefit to using HUNDRED is to find the several methods which use the same magic number (in your example it's used by getPercent and getRate).

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edited Mar 11, 2014 at 10:41

ChrisW

13.1k
1
35
76

Speaking as a human programmer (i.e. I am not Lint software), your use of "100" there looks fine to me.

Wikipedia has an article (without citations) titled Accepted limited use of magic numbers: IMO your "100" is in the same category as these other "accepted" magic numbers.

This Wiki describing magic numbers says two things.

Firstly,

Practical Magic Number rule: A literal is a not a magic number if the most meaningful variable name for it is the same as the spoken name of the literal.

That's applicable here: you're looking for a named constant like HUNDRED or CENTUM.

Secondly, it also suggests loading "magic" numbers (e.g. a "discount rate") from a configuration file:

static final double DISCOUNT_PERCENT = getProperty( "sales.discount_percent" );
static final double DISCOUNT_FACTOR = 1 - (DISCOUNT_PERCENT / 100);

// ...

salePrice = DISCOUNT_FACTOR * regularPrice;

Note that though this example code carefully loaded DISCOUNT_PERCENT from a configuration, the "100" used to calculate the DISCOUNT_FACTOR is hard-coded.

If you use "100" instead of HUNDRED, it's easier for a programmer to understand, and to verify that it's correct.

IMO the only benefit to using HUNDRED is to find the several methods which use the same magic number (in your example it's used by getPercent and getRate).

Speaking as a human programmer (i.e. I am not Lint software), your use of "100" there looks fine to me.

Wikipedia has an article (without citations) titled Accepted limited use of magic numbers: IMO your "100" is in the same category as these other "accepted" magic numbers.

Speaking as a human programmer (i.e. I am not Lint software), your use of "100" there looks fine to me.

Wikipedia has an article (without citations) titled Accepted limited use of magic numbers: IMO your "100" is in the same category as these other "accepted" magic numbers.

This Wiki describing magic numbers says two things.

Firstly,

Practical Magic Number rule: A literal is a not a magic number if the most meaningful variable name for it is the same as the spoken name of the literal.

That's applicable here: you're looking for a named constant like HUNDRED or CENTUM.

Secondly, it also suggests loading "magic" numbers (e.g. a "discount rate") from a configuration file:

static final double DISCOUNT_PERCENT = getProperty( "sales.discount_percent" );
static final double DISCOUNT_FACTOR = 1 - (DISCOUNT_PERCENT / 100);

// ...

salePrice = DISCOUNT_FACTOR * regularPrice;

Note that though this example code carefully loaded DISCOUNT_PERCENT from a configuration, the "100" used to calculate the DISCOUNT_FACTOR is hard-coded.

If you use "100" instead of HUNDRED, it's easier for a programmer to understand, and to verify that it's correct.

IMO the only benefit to using HUNDRED is to find the several methods which use the same magic number (in your example it's used by getPercent and getRate).

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answered Mar 11, 2014 at 10:21

ChrisW

13.1k
1
35
76

Speaking as a human programmer (i.e. I am not Lint software), your use of "100" there looks fine to me.

Wikipedia has an article (without citations) titled Accepted limited use of magic numbers: IMO your "100" is in the same category as these other "accepted" magic numbers.

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