# String#sub with ascii string fails to cache Regexp

**URL:** <https://www.ruby-forum.com/t/string-sub-with-ascii-string-fails-to-cache-regexp/129124>\
**Category:** Development\
**Created:** [February 14, 2008, 5:27pm UTC](https://www.ruby-forum.com/t/string-sub-with-ascii-string-fails-to-cache-regexp/129124 "2008-02-14T17:27:36Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Yusuke\_ENDOH](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/y/c89c15/32.png) [@Yusuke\_ENDOH](https://www.ruby-forum.com/u/Yusuke_ENDOH)\
**Post date:** [February 14, 2008, 5:27pm UTC](https://www.ruby-forum.com/t/string-sub-with-ascii-string-fails-to-cache-regexp/129124/1 "2008-02-14T17:27:36Z")

</div>

e$B1sF#$G$9!#e(B

sub e$B$de(B gsub e$B$OBh0l0z?t$,J8;zNs$N;~!"$=$NJ8;zNs$re(B  
rb\_reg\_quote  
e$B$7$?$b$N$re(B rb\_reg\_regcomp e$B$G%-%c%C%7%e$7$^$9!#e(B

$ time LANG=C ./ruby -ve ‘n = “\u3042” \* 1000; 30000.times { “”.sub!(n,  
“”) }’  
ruby 1.9.0 (2008-02-14 revision 15475) [i686-linux]

real 0m1.340s  
user 0m1.300s  
sys 0m0.030s

e$B$G$b!"$=$NJ8;zNs$,e(B ascii  
e$B$N$\_$G$"$k\>l9g$O%-%c%C%7%e$K\<:GT$9$ke(B  
e$B$h$&$G$9!#e(B

$ time LANG=C ./ruby -ve ‘n = “abc” \* 1000; 30000.times { “”.sub!(n, “”)  
}’  
ruby 1.9.0 (2008-02-14 revision 15475) [i686-linux]

real 0m32.840s  
user 0m32.560s  
sys 0m0.030s

rb\_reg\_quote e$B$NJV$7$?J8;zNs$N%(%s%3!\<%G%#%s%0$,e(B ASCII-8BIT  
e$B$G!“e(B  
e$B%-%c%C%7%e$Ne(B Regexp e$B$N%(%s%3!\<%G%#%s%0$,e(B US-ASCII  
e$B$G?)$$0c$C$Fe(B  
e$B$$$k$?$a!”%-%c%C%7%e$Ne(B Regexp e$B$,:FMxMQ$5$l$J$$$h$&$G$9!#e(B