binary-decision-diagram/src/minimal-string/string-format.ts

A library to create, minimize and optimize binary decision diagrams

/*
let t = 0;
while (t < 10000) {
    const char = String.fromCharCode(t);
    console.log(t + ' : ' + char);
    t++;
}
*/

/*

To have a really small string representation, we have to hack some stuff
which makes is complicated but effective.

Rules for the string:
- The string starts with a number like '23' that defines how many leaf-nodes we have
- leaf nodes consist of two chars like 'ab'
    - the first char is the id
    - the second the value is a number you can get via String.charCodeAt()
- Internal nodes have four chars like 'abcd'
    - the first char is the id
    - the second char is the id of the 0-branch
    - the third char is the id of the 1-branch
    - the last char is the id of the boolean-function (= level)
- The last 3 chars of the string is the root node like 'abc'
    - it looks like the internal-node but without the id (first char)

*/

// we use this because 39 is the quotes which causes problems
export const CHAR_CODE_OFFSET = 40; // String.fromCharCode(33) === ')'


export function getCharOfLevel(level: number): string {
    const charCode = CHAR_CODE_OFFSET + level;
    return String.fromCharCode(charCode);
}

export function getNumberOfChar(char: string): number {
    const charCode = char.charCodeAt(0);
    return charCode - CHAR_CODE_OFFSET;
}

export function getCharOfValue(value: number): string {
    const charCode = CHAR_CODE_OFFSET + value;
    return String.fromCharCode(charCode);
}


export const FIRST_CHAR_CODE_FOR_ID = 97; // String.fromCharCode(97) === 'a'

export function getNextCharId(lastCode: number): {
    char: string,
    nextCode: number
} {

    // jump these codes because they look strange
    if (lastCode >= 128 && lastCode <= 160) {
        lastCode = 161;
    }

    const char = String.fromCharCode(lastCode);
    return {
        char,
        nextCode: lastCode + 1
    };
}