How can I improve my regular expressions?

Here are two txt files(frt_susp_sub.txt and rr_susp_sub.txt) and I'd like to extract spring and damper name from each file as shown in the picture below.

This is my code

clc

clear all

str1 = fileread('frt_susp_sub.txt');

frt_spr_assy_xpr = '(?<=SPRING_ASSEMBLY.+?springs.tbl/).+?(?=.spr)';

frt_dpr_assy_xpr = '(?<=DAMPER_ASSEMBLY.+?dampers.tbl/).+?(?=.dpr)';

frt_spr_assy = regexp(str1, frt_spr_assy_xpr, 'match', 'once');

frt_dpr_assy = regexp(str1, frt_dpr_assy_xpr, 'match', 'once');

str2 = fileread('rr_susp_sub.txt');

rr_spr_assy_xpr = '(?<=SPRING_ASSEMBLY.+?springs.tbl/).+?(?=.spr)';

rr_dpr_assy_xpr = '(?<=DAMPER_ASSEMBLY.+?dampers.tbl/).+?(?=.dpr)';

rr_spr_assy = regexp(str2, rr_spr_assy_xpr, 'match', 'once');

rr_dpr_assy = regexp(str2, rr_dpr_assy_xpr, 'match', 'once');

It works well as I expected but the performance is pretty bad.

How can I improve my code?

Answer 1

[Stephen23]

Get rid of the look-behind expressions. They don't restrict which block of data is being read anyway.

Also note that '.' matches any character, whereas '\.' matches a period character only.

Also get rid of cargo-cult CLC and CLEAR ALL.

str1 = fileread('frt_susp_sub.txt');
frt_spr_assy = regexp(str1, '\w+(?=\.spr)', 'match', 'once')

frt_spr_assy = 'name13'

frt_dpr_assy = regexp(str1, '\w+(?=\.dpr)', 'match', 'once')

frt_dpr_assy = 'name14'

It may be faster to avoid the look-ahead:

tmp = regexp(str1, '(\w+)\.spr', 'tokens', 'once');
frt_spr_assy = tmp{1}

frt_spr_assy = 'name13'

[Munho Noh]

Thank you Stephen. It works much faster.