number.md

Example: <number>

The following example parses floating-point numbers and integers. In both the scientific notation can be used.

entry {
    <raw-num> = [(\d)+]
    <num-sign> = [ '+' | '-' ]
    <scientific-notation> = ['e' <num-sign>? <raw-num>]
    <scientific-num> = [<raw-num> <scientific-notation>?]
    
    default [object:
    
        # Well that's optional
        def sign = [<num-sign>]?

        # Decimal
        [
            def num = [<raw-num>]? '.' 
            def decimal = [<scientific-num>]
        ] |
    
        # Non-decimal
        def num = [<scientific-num>]
    ]
}

The definition contains three tags:

1. num contains the preceding number.
2. decimal contains the decimal-place.
3. sign contains (an optional) preceding sign (+ or -).

Valid inputs:

Input	Output
parse('10')	{sign: null, num: '10', decimal: null}
parse('-25')	{sign: '-', num: '25', decimal: null}
parse('14.5')	{sign: null, num: '14', decimal: '5'}
parse('20e+55')	{sign: null, num: '20e+55', decimal: null}
parse('10.5e6')	{sign: null, num: '10', decimal: '5e6'}
parse('-.5e2')	{sign: '-', num: null, decimal: '5e2'}
parse('.23e-232')	{sign: null, num: null, decimal: '23e-232'}

Invalid inputs:

Input	Output
parse(g)	null (not a number)
parse(.35.34)	null (number cannot contain two decimal places)
parse(2e5.3e5)	null (scientific notation cannot be used in both places)
parse(-+5)	null (two preceding signs are not allowed)