Re: Operations on RegularExpression matches
- To: mathgroup at smc.vnet.net
- Subject: [mg120001] Re: Operations on RegularExpression matches
- From: Albert Retey <awnl at gmx-topmail.de>
- Date: Tue, 5 Jul 2011 05:09:23 -0400 (EDT)
- References: <ius5nq$2g4$1@smc.vnet.net>
Hi, > > I have string of all lower case letters: > > string = "this is a string" > > I wish to capitalize the first letter: > > StringReplace[string, StartOfString ~~ x_ -> ToUpperCase[x]] (* Does want I want *) > > Now I try to do the same thing using RegularExpression: > > StringReplace[string, RegularExpression["(^.)"] -> ToUpperCase["$1"]] > > which fails (returns original string without capitalization). > > I know the match is occurring since > > StringReplace[string, RegularExpression["(^.)"] -> ToUpperCase["$1X"]] > > returns > > "tXhis is a string" > > What am I missing about using the matched part of a regular expression? the problem is that ToUpperCase is done on the pattern, not the match. You need RuleDelayed so that ToUpperCase is done on the matching string: StringReplace[string, RegularExpression["(^.)"] :> ToUpperCase["$1"]] this is not necessary with the StringExpression approach since then ToUpperCase[x] remains unevaluated since x is no string. hth, albert