Number generation in words from any arbitrary number

Once I needed to write the generation of the amount in words for one project. The search for ready-made solutions led nowhere; as a result, a small C ++ class was born that generates a capital equivalent of a number. As a nice bonus, I added there to support rubles and dollars (this was required for that project). Under the cut a bit of theory and a link to the Git-repository.

Theory

Names of Numbers

In Russian, the numbers from 1 to 9 (the so-called ones ) and from 10 to 20 (the second row of ones) have individual names. After 20 individual names have dozens , and the number is formed by adding to the name tens of the number of categories from the category of units.

Example:

• 5 - five
• 17 - seventeen
• 23 - twenty three
• 48 - forty eight

Hundreds include tens and units , and thousands contain all of the above names. And so, as the order of the number increases, that is, each new order includes all the previous ones.
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Female and male gender order names

There is the following feature. When forming a number less than 100, there are no problems, but when forming a capital equivalent of large sums, you will have words denoting orders of hundreds, tens and units, namely thousands, millions, etc.

There are such variants of numbers:

• one thousand
• one million
• two million
• two thousand
• five thousand

etc.

The rules are:

1. For the names of feminine orders, it is necessary to modify 1 and 2 ( one , two );
2. For both genera, the endings of the names of the orders for the number 1, groups from 2 to 4 and further to 20 (including the second row of units from 11 to 19) are differently inclined.

Example:

• 1 (one) thousand a
• 2-3-4 thousand and
• 5-19 thousand

• 1 million
• 2-3-4 million a
• 5-20 million s

Knowing these features, it is possible to draw up the logic of the generator of the capital number.

Class

The number generation mechanism works as follows:

1. Having received a number at the input, we determine the digit of the number (millions, thousands or less);
2. For each order except we generate hundreds, tens and units, appending the name of the order at the end.

This is how the C ++ class Propis was born . From a double value, the output is a string with an uppercase value and a currency of the number (if available) with an accuracy of hundredths. The generation of numbers up to 1 billion is implemented, if necessary, you can easily make support for billions and above. It depends only on the standard cmath and std :: string library.

Example of use in C ++ code:

Propis *propis = new Propis; double value = 345.12; //        std::string resultString = propis->conv(value, Propis::Dollar); // "   ,  " 

An example of use in an iOS program:

 - (IBAction)valueChanged:(UITextField *)sender { Propis propis; double value = [sender.text doubleValue]; std::string stdResultString = propis.conv(value, Propis::NoCurrency); NSString *resultString = [NSString stringWithUTF8String:stdResultString.c_str()]; self.resultView.text = resultString; } 

The git repository with class source code is here . I would be glad if someone come in handy.