why emacs lisp's regex has 2-steps escapes?

[Xah]

emacs regex has a odd pecularity in that it needs a lot backslashes.
More specifically, a string first needs to be properly escaped, then
this passed to the regex engine.

For example, suppose you have this text “Sin[x] + Sin[y]” and you need
to capture the x or y.

In emacs i need to use
“\\(\\[[a-z]\\]\\)”
for the actual regex
“\(\[[a-z]\]\)”.

Here's somewhat typical but long regex for matching a html image tag

(search-forward-regexp "<img +src=\"\\([^\"]+\\)\" +alt=\"\\([^\"]+\\)?
\" +width=\"\\([0-9]+\\)\" +height=\"\\([0-9]+\\)\" ?>" nil t)

The toothpick syndrom gets crazy making already difficult regex syntax
impossible to read and hard to code.

My question is, why is elisp's regex has this 2-steps process? Is this
some design decision or just happened that way historically?

Second question: can't elisp create some like “regex-string” wrapper
function that automatically takes care of the quoting? I can't see how
this migth be difficult?

Thanks.

  Xah
∑ http://xahlee.org/

☄