2022-09-26

26th September 2022

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Write a function to output the ordinal suffix of a positive integer concatenated to an inputted number.

Example:

> ordinal(3)
> '3rd'

> ordinal(57)
> '57th'

Solution

Take number, get the value for the ones and the tens. Use modulo operator to figure out the value. Because the inputs are uint64 to enforce positive integerness and large enough space and make it easy to deal with FormatUint method, I can divide that by 10 which will discard the ones, so I can modulo that number to get the tens.

In English, rules for ordinals are:

• every number that ends in a 1 gets a "st" suffix
• except numbers that end in 11, which get a "th" suffix
• numbers that end in 2 get a "nd" suffix
• except numbers that end in 12, they get "th"
• numbers that end in 3 get a "rd" suffix
• except numbers that end in 13, they get "th"

Switch rules:

• if the value of tens is 1, get a th
• if the value of ones is 1, get a st
• if the value of ones is 2, get a nd
• if the value of ones is 3, get a rd
• everything else gets a th