Regular Expression Replacement

apoch632

I have a basic enough question regarding regular expression

I have a number that begins with 8 and that may have any number of following digits

I want to be able to replace that first digit (which will always be 8) with a 5.

The code I have so far to extract the 8 is

^(8)\d+

Can anyone describe to me how to change this first digit to a 5?

Webmonkey

apoch632 wrote: »

I have a basic enough question regarding regular expression

I have a number that begins with 8 and that may have any number of following digits

I want to be able to replace that first digit (which will always be 8) with a 5.

The code I have so far to extract the 8 is

^(8)\d+

Can anyone describe to me how to change this first digit to a 5?

We aren't psychic you know! What language are you working with?

syklops

Im psychic. Its ruby he is referring to. :cool:

boblong

syklops wrote: »

Im psychic. Its ruby he is referring to. :cool:

Really?

I'm not cool enough to know Ruby, but would a simple:

>> a = "8544321"
=> "8544321"
>> a.sub(/8/,"5")
=> "5544321"

... not work? I'm don't know if your "numbers" are strings or whatever or why you want to use a regex but there you go - "gsub" should replace ALL "8"s with "5"s if that's what you want.

Others:

>> a.sub(/./,"5")
=> "5544821"

Depending on what it is you want exactly.

Sorry if I've misinterpreted your question, I'm a bit tired

apoch632

My apologies, it is ruby I am using

I don't want to replace all instances of 8 just the first one

Webmonkey

If 8 will always be the first number why don't you just replace it without using reg expressions.

Don't know ruby but

str[0] = "5"?

Or am I mis reading your question.

boblong

apoch632 wrote: »

My apologies, it is ruby I am using

I don't want to replace all instances of 8 just the first one

Regexes are a bit of an odd fit, but yes using sub() will only replace the first '8'. gsub() will replace all of the '8's.

stesh

boblong wrote: »

Regexes are a bit of an odd fit, but yes using sub() will only replace the first '8'. gsub() will replace all of the '8's.

With the first '8' not necessarily being the first digit of the number.