SAS9新体验－在DATA STEP中使用perl 正则表达式支持（Regular Expressions）

sas自9版开始支持perl（Perl 5.6.1 ） 正则表达式支持，极大的方便了数据校验的简易性、可靠性
在没有Regular Expressions（RE）前，只能使用index,substr,tranwrd等函数对字符串进行操作，但这些函数对动态字符串的操作是缺乏弹性且效率较低
故SAS9推出RE，以方便的进行字符串校验、替换、提取
Regexp是由一组被称为metacharacters的特殊字符组成，这些特殊字符代表着特殊的匹配规则，具体请参考
http://www.perldoc.com/perl5.6.1/pod/perlre.html

各种使用案例如下：
1、对客户数据中的电话号码进行数据校验
data _null_;
   retain re;
   length first last home business $ 16;

   if _N_ = 1 then do;
      /*设置电话匹配模式1 (XXX) XXX-XXXX */
      paren = "/([2-9]/d/d/) ?[2-9]/d/d-/d/d/d/d";
   
      /*设置电话匹配模式2 XXX-XXX-XXXX */
      dash = "[2-9]/d/d-[2-9]/d/d-/d/d/d/d";

      /* 合并两种匹配模式，使用【|】特殊符号 */
      regexp = "/(" || paren || ")|(" || dash || ")/";
   /*判断是否为正确的正则表达式*/
      re = prxparse(regexp);
      if missing(re) then do;
         putlog "ERROR: Invalid regexp " regexp;
         stop;
      end;
   end;

   input first last home business;
 /*启用正则匹配，如果匹配失败则返回missing*/
   if ^prxmatch(re, home) then
      putlog "NOTE: Invalid home phone number for " first last home;
   if ^prxmatch(re, business) then
      putlog "NOTE: Invalid business phone number for " first last business;
datalines;
Jerome Johnson (919)319-1677 (919)846-2198
Romeo Montague 800-899-2164 360-973-6201
Imani Rashid (508)852-2146 (508)366-9821
Palinor Kent . 919-782-3199
Ruby Archuleta . .
Takei Ito 7042982145 .
Tom Joad 209/963/2764 2099-66-8474
;
输出结果如下:
NOTE: Invalid home phone number for Palinor Kent
NOTE: Invalid home phone number for Ruby Archuleta
NOTE: Invalid business phone number for Ruby Archuleta
NOTE: Invalid home phone number for Takei Ito 7042982145
NOTE: Invalid business phone number for Takei Ito
NOTE: Invalid home phone number for Tom Joad 209/963/2764
NOTE: Invalid business phone number for Tom Joad 2099-66-84

2、替换字符串，把<替换为<把>替换为>
data _null_;
   retain lt_re gt_re;
   if _N_ = 1 then do;
     /*设置替换模式 格式为：s/正则匹配表达式/替换的文本/*/
      lt_re = prxparse('s/</');
     
      gt_re = prxparse('s/>/>/');
      if missing(lt_re) or missing(gt_re) then do;
         putlog "ERROR: Invalid regexp.";
         stop;
      end;
   end;

   input;
   /*启用这则替换*/
   call prxchange(lt_re, -1, _infile_);
   call prxchange(gt_re, -1, _infile_);

   put _infile_;
datalines4;
The bracketing construct ( ... ) creates capture buffers.
To refer to the digit'th buffer use / within the match.
Outside the match use "$" instead of "/". (The /
notation works in certain circumstances outside the match.
See the warning below about /1 vs $1 for details.) Referring
back to another part of the match is called a backreference.
;;;;

输出结果如下:
The bracketing construct ( ... ) creates capture buffers.
To refer to the digit'th buffer use /<digit> within the match.
Outside the match use "$" instead of "/". (The /<digit>
notation works in certain circumstances outside the match.
See the warning below about /1 vs $1 for details.) Referring
back to another part of the match is called a backreference.
3、从客户信息中提取客户的办公电话文本
data _null_;
   retain re areacode_re;
   length first last home business $ 16;
   length areacode $ 3;

   if _N_ = 1 then do;
      /* (XXX) XXX-XXXX */
      paren = "/(([2-9]/d/d)/) ?[2-9]/d/d-/d/d/d/d";

      /* XXX-XXX-XXXX */
      dash = "([2-9]/d/d)-[2-9]/d/d-/d/d/d/d";

      /* Combine two phone patterns into one with a | */
      regexp = "/(" || paren || ")|(" || dash || ")/";

      re = prxparse(regexp);
      if missing(re) then do;
         putlog "ERROR: Invalid regexp " regexp;
         stop;
      end;

      areacode_re = prxparse("/828|336|704|910|919|252/");
      if missing(areacode_re) then do;
         putlog "ERROR: Invalid area code regexp";
         stop;
      end;
   end;

   input first last home business;

   if ^prxmatch(re, home) then
      putlog "NOTE: Invalid home phone number for " first last home;
 
   if prxmatch(re, business) then do;
     /*返回最后匹配结果的信息*/
      which_format = prxparen(re);
      /*从匹配结果中提取字符串*/
      call prxposn(re, which_format, pos, len);
      areacode = substr(business, pos, len);
      /*判断提取出的字符串的区号是否匹配，匹配则输出结果*/
      if prxmatch(areacode_re, areacode) then
         put "In North Carolina: " first last business;
   end;
   else
      putlog "NOTE: Invalid business phone number for " first last business;
datalines;
Jerome Johnson (919)319-1677 (919)846-2198
Romeo Montague 800-899-2164 360-973-6201
Imani Rashid (508)852-2146 (508)366-9821
Palinor Kent 704-782-4673 704-782-3199
Ruby Archuleta 905-384-2839 905-328-3892
Takei Ito 704-298-2145 704-298-4738
Tom Joad 515-372-4829 515-389-2838
;

输出结果如下:
In North Carolina: Jerome Johnson (919)846-2198
In North Carolina: Palinor Kent 704-782-3199
In North Carolina: Takei Ito 704-298-4738

以上源代码来自SAS网站，我只是稍微加了点注释，便于初次接触者了解，详情请参考SAS网站