regex101: LDraw valid numbers and invalid formats capture

Positive Lookbehind(?<=[ \t])

Character Class[ \t]

the literal (32₁₀ / 40₈ / 20₁₆)

\ta tab character (ASCII 9)

-?optionally matches the literal - (45₁₀ / 55₈ / 2D₁₆)

Non-Capturing Group(?: (?: \d |[1-9]\d+ |[1-9]\d*\.\d{1,3}(?<!0) |\.\d{1,3}(?<!0) )|(?: (\.0*)0 |(0+)\.\d{0,2}[1-9] |(0+)(?:0|[1-9]\d*)\.?\d* |\d+(\.0*) |\d*\.(?:[1-9]|\d[1-9])?(0+) |\d*\.\d{3}(\d+) ) )

1st Alternative (?: \d |[1-9]\d+ |[1-9]\d*\.\d{1,3}(?<!0) |\.\d{1,3}(?<!0) )

Non-Capturing Group(?: \d |[1-9]\d+ |[1-9]\d*\.\d{1,3}(?<!0) |\.\d{1,3}(?<!0) )

1st Alternative \d

\da digit

2nd Alternative[1-9]\d+

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

\d+a digit, repeated at least once

3rd Alternative[1-9]\d*\.\d{1,3}(?<!0)

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

\d*a digit, repeated any number of times

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

Negative Lookbehind(?<!0)

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

4th Alternative\.\d{1,3}(?<!0)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{1,3}a digit, repeated between 1 and 3 times

Negative Lookbehind(?<!0)

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

2nd Alternative(?: (\.0*)0 |(0+)\.\d{0,2}[1-9] |(0+)(?:0|[1-9]\d*)\.?\d* |\d+(\.0*) |\d*\.(?:[1-9]|\d[1-9])?(0+) |\d*\.\d{3}(\d+) )

Non-Capturing Group(?: (\.0*)0 |(0+)\.\d{0,2}[1-9] |(0+)(?:0|[1-9]\d*)\.?\d* |\d+(\.0*) |\d*\.(?:[1-9]|\d[1-9])?(0+) |\d*\.\d{3}(\d+) )

1st Alternative (\.0*)0

Group 1(\.0*)

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

0*the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated any number of times

0 the literal text 0

2nd Alternative(0+)\.\d{0,2}[1-9]

Group 2(0+)

0+the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated at least once

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d{0,2}a digit, repeated between 0 and 2 times

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

3rd Alternative(0+)(?:0|[1-9]\d*)\.?\d*

Group 3(0+)

0+the literal 0 (48₁₀ / 60₈ / 30₁₆) , repeated at least once

Non-Capturing Group(?:0|[1-9]\d*)

1st Alternative0

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

2nd Alternative[1-9]\d*

Character Class[1-9]

\d*a digit, repeated any number of times

\.?optionally matches the literal . (46₁₀ / 56₈ / 2E₁₆)

\d*a digit, repeated any number of times

4th Alternative\d+(\.0*)

5th Alternative\d*\.(?:[1-9]|\d[1-9])?(0+)

6th Alternative\d*\.\d{3}(\d+)

Positive Lookahead(?=[ \t]|$)

Character Class[ \t]?

Global pattern flags

x modifier: extended. Ignores unescaped whitespace and comments outside character classes

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Search reference

Regular Expression

(?<=[ \t])-?
(?:
(?:
	\d
	|[1-9]\d+
	|[1-9]\d*\.\d{1,3}(?<!0)
	|\.\d{1,3}(?<!0)
)|(?:
	(\.0*)0
	|(0+)\.\d{0,2}[1-9]
	|(0+)(?:0|[1-9]\d*)\.?\d*
	|\d+(\.0*)
	|\d*\.(?:[1-9]|\d[1-9])?(0+)
	|\d*\.\d{3}(\d+)
)
)
(?=[ \t]|$)[ \t]?

New

Valid:
* Integers
 0 1 10 123
 -0 -1 -10 -123
* Floats <1, without leading zero, (1<=precision<=3)
 .1 .01 .001 .12 .123
 -.1 -.01 -.001 -.12 -.123
* Floats >1, (1<=precision<=3)
 1.1 1.01 1.001 1.12 1.123 12.1 12.12 12.123 123.1 123.12 123.123
 -1.1 -1.01 -1.001 -1.12 -1.123 -12.1 -12.12 -12.123 -123.1 -123.12 -123.123

Invalid (in order of capture):
* [1] Zero as float with only trailing zeros
 .0 .00 .000
 -.0 -.00 -.000
* [2] Floats <1, with leading zero
 0.1 0.01 0.001 0.12 0.123
 -0.1 -0.01 -0.001 -0.12 -0.123
* [3] Integers with leading zeros
 00 01 012 0123 000 001 0012 00123 0000 0001 00012 000123
 -00 -01 -012 -0123 -000 -001 -0012 -00123 -0000 -0001 -00012 -000123
* [4] Integers as float ('fake floats')
 0. 1. 12. 123.
 0.0 0.00 0.000 0.0000
 1.0 1.00 1.000
 -0. -1. -12. -123.
 -0.0 -0.00 -0.000 -0.0000
 -1.0 -1.00 -1.000
* [5] Floats with trailing zeros
 1.10 1.100 1.120 .10 .100 .120
 -1.10 -1.100 -1.120 -.10 -.100 -.120
* [6] Any float with precision >3
 0.0001 0.0012 0.0123 0.1234
 1.0001 1.0012 1.0123 1.1234
 10.0001 10.0012 10.0123 10.1234
 100.0001 100.0012 100.0123 100.1234
 -0.0001 -0.0012 -0.0123 -0.1234
 -1.0001 -1.0012 -1.0123 -1.1234
 -10.0001 -10.0012 -10.0123 -10.1234
 -100.0001 -100.0012 -100.0123 -100.1234