I am trying to create a regex to match several different dimensional patterns and their units.

Below are examples of the patterns. The numbers can be an integer, or a decimal. The dimensional separator can be: "x", "by" or "transverse by". The units are cm or mm

3.4 x 2 cm

3.4 by 2 cm

3.4 mm x 2.0 mm

3.4 cm x 2.0 cm x 2 cm

3.4 x 2 x 2.0 x 2 cm

3.4 cm x 2 cm transverse by 2.0 cm

3.4 transverse by 2.0 cm

3.4 mm transverse by 2.0 mm

4 cm

4.5 cm

So far I have the following:

(\d (\.\d |)\s?(x|by)\s?\d (\.\d |)(\s?(x|by)\s?\d*(\.?\d |))?) (cm|mm)

But it doesn't pick up "transverse by", 3.4 mm x 2.0 mm, or 3 mm

Thanks in advance!

CodePudding user response：

I'm assuming you are using JavaScript or a Perl-compatible library. The following Regex uses pretty common features, so you should be good with most.

See an example on regexr

((\d*\.)?\d (\s*(cm|mm))?\s*(x|(transverse )?by)\s*)*(\d*\.)?\d (\s*(cm|mm))?

Explanation

Let's start with the end:

(\d*\.)?\d (\s*(cm|mm))?

This will match a decimal value ((\d*\.)?\d ) followed by an optional unit (cm or mm).

This will match simple text like:

• 4 cm
• 4.5 cm

Next is the prefix expression:

((\d*\.)?\d (\s*(cm|mm))?\s*(x|(transverse )?by)\s*)*

This breaks down into two parts:

The same expression we used before to match a number with a unit:

(\d*\.)?\d (\s*(cm|mm))?

followed by some separator (e.g. " x ", " by " and " transverse by ") text:

\s*(x|(transverse )?by)\s*

Zero more prefixes are allowed, so you could match n-dimensional sizes:

• 4.5 cm x 55 mm by 105.3 transverse by 12.001 cm x 9 mm

If you want to constrain to 3-dimensional shapes, then instead of a * you can use {,2}:

((\d*\.)?\d (\s*(cm|mm))?\s*(x|(transverse )?by)\s*){,2}

CodePudding user response：

To get the full matches, you can write the pattern as:

^\d (?:\.\d )?(?:\s [cm]m)?(?:\s (?:x|(?:transverse\s )?by)\s \d(?:\.\d )?(?:\s [cm]m)?)*$

Explanation

• ^ Start of string
• \d (?:\.\d )? Match 1 digits with an optional decimal part
• (?:\s [cm]m)?
• (?: Non capture group to repeat as a whole part with alternations
  • \s Match 1 whitespace chars
  • (?:x|(?:transverse\s )?by) Match either x or transverse by or by
  • \s Match 1 whitespace chars
  • \d(?:\.\d )? Match 1 digits with an optional decimal part
  • (?:\s [cm]m)? Optionally match 1 whitespace chars and either cm or mm
• )* Close the non capture group and optionally repeat
• $ End of string

See a regex demo.

If you also want to match decimals starting with a dot like .5 mm

^(\d*\.)?\d (?:\s [cm]m)?(?:\s (?:x|(?:transverse\s )?by)\s (\d*\.)?\d (?:\s [cm]m)?)*$

Regex demo