[PATCH v3 3/6] userdiff-cpp: tighten word regex

["Johannes Sixt via GitGitGadget" <gitgitgadget@xxxxxxxxx>]

From: Johannes Sixt <j6t@xxxxxxxx>

Generally, word regex can be written such that they match tokens
liberally and need not model the actual syntax because it can be assumed
that the regex will only be applied to syntactically correct text.

The regex for cpp (C/C++) is too liberal, though. It regards these
sequences as single tokens:

   1+2
   1.5-e+2+f

and the following amalgams as one token:

   .l      as in str.length
   .f      as in str.find
   .e      as in str.erase

Tighten the regex in the following way:

- Accept + and - only in one position in the exponent. + and - are no
  longer regarded as the sign of a number and are treated by the
  catcher-all that is not visible in the driver's regex.

- Accept a leading decimal point only when it is followed by a digit.

For readability, factor hex- and binary numbers into an own term.

As a drive-by, this fixes that floating point numbers such as 12E5
(with upper-case E) were split into two tokens.

Signed-off-by: Johannes Sixt <j6t@xxxxxxxx>
---
 t/t4034/cpp/expect | 16 ++++++++--------
 userdiff.c         |  8 +++++++-
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/t/t4034/cpp/expect b/t/t4034/cpp/expect
index 63e53a61e62..46c9460a968 100644
--- a/t/t4034/cpp/expect
+++ b/t/t4034/cpp/expect
@@ -3,24 +3,24 @@
 <BOLD>--- a/pre<RESET>
 <BOLD>+++ b/post<RESET>
 <CYAN>@@ -1,30 +1,30 @@<RESET>
-Foo() : x(0<RED>&&1<RESET><GREEN>&42<RESET>) { <RED>foo0<RESET><GREEN>bar<RESET>(x<RED>.f<RESET><GREEN>.F<RESET>ind); }
+Foo() : x(0<RED>&&1<RESET><GREEN>&42<RESET>) { <RED>foo0<RESET><GREEN>bar<RESET>(x.<RED>find<RESET><GREEN>Find<RESET>); }
 cout<<"Hello World<RED>!<RESET><GREEN>?<RESET>\n"<<endl;
-<GREEN>(<RESET>1 <RED>-1e10<RESET><GREEN>+1e10<RESET> 0xabcdef<GREEN>)<RESET> '<RED>x<RESET><GREEN>y<RESET>'
+<GREEN>(<RESET>1 <RED>-<RESET><GREEN>+<RESET>1e10 0xabcdef<GREEN>)<RESET> '<RED>x<RESET><GREEN>y<RESET>'
 // long double<RESET>
 <RED>3.141592653e-10l<RESET><GREEN>3.141592654e+10l<RESET>
 // float<RESET>
-120<RED>E5f<RESET><GREEN>E6f<RESET>
+<RED>120E5f<RESET><GREEN>120E6f<RESET>
 // hex<RESET>
-<RED>0xdeadbeaf+8<RESET><GREEN>0xdeadBeaf+7<RESET>ULL
+<RED>0xdeadbeaf<RESET><GREEN>0xdeadBeaf<RESET>+<RED>8ULL<RESET><GREEN>7ULL<RESET>
 // octal<RESET>
 <RED>01234567<RESET><GREEN>01234560<RESET>
 // binary<RESET>
 <RED>0b1000<RESET><GREEN>0b1100<RESET>+e1
 // expression<RESET>
-<RED>1.5-e+2+f<RESET><GREEN>1.5-e+3+f<RESET>
+1.5-e+<RED>2<RESET><GREEN>3<RESET>+f
 // another one<RESET>
-str<RED>.e+65<RESET><GREEN>.e+75<RESET>
-[a] b<RED>-><RESET><GREEN>->*<RESET>v d<RED>.e<RESET><GREEN>.*e<RESET>
+str.e+<RED>65<RESET><GREEN>75<RESET>
+[a] b<RED>-><RESET><GREEN>->*<RESET>v d<RED>.<RESET><GREEN>.*<RESET>e
 <GREEN>~<RESET>!a <GREEN>!<RESET>~b c<RED>++<RESET><GREEN>+<RESET> d<RED>--<RESET><GREEN>-<RESET> e*<GREEN>*<RESET>f g<RED>&<RESET><GREEN>&&<RESET>h
 a<RED>*<RESET><GREEN>*=<RESET>b c<RED>/<RESET><GREEN>/=<RESET>d e<RED>%<RESET><GREEN>%=<RESET>f
 a<RED>+<RESET><GREEN>++<RESET>b c<RED>-<RESET><GREEN>--<RESET>d
@@ -30,6 +30,6 @@ a<RED>==<RESET><GREEN>!=<RESET>b c<RED>!=<RESET><GREEN>=<RESET>d
 a<RED>^<RESET><GREEN>^=<RESET>b c<RED>|<RESET><GREEN>|=<RESET>d e<RED>&&<RESET><GREEN>&=<RESET>f
 a<RED>||<RESET><GREEN>|<RESET>b
 a?<GREEN>:<RESET>b
-a<RED>=<RESET><GREEN>==<RESET>b c<RED>+=<RESET><GREEN>+<RESET>d <RED>e-=f<RESET><GREEN>e-f<RESET> g<RED>*=<RESET><GREEN>*<RESET>h i<RED>/=<RESET><GREEN>/<RESET>j k<RED>%=<RESET><GREEN>%<RESET>l m<RED><<=<RESET><GREEN><<<RESET>n o<RED>>>=<RESET><GREEN>>><RESET>p q<RED>&=<RESET><GREEN>&<RESET>r s<RED>^=<RESET><GREEN>^<RESET>t u<RED>|=<RESET><GREEN>|<RESET>v
+a<RED>=<RESET><GREEN>==<RESET>b c<RED>+=<RESET><GREEN>+<RESET>d e<RED>-=<RESET><GREEN>-<RESET>f g<RED>*=<RESET><GREEN>*<RESET>h i<RED>/=<RESET><GREEN>/<RESET>j k<RED>%=<RESET><GREEN>%<RESET>l m<RED><<=<RESET><GREEN><<<RESET>n o<RED>>>=<RESET><GREEN>>><RESET>p q<RED>&=<RESET><GREEN>&<RESET>r s<RED>^=<RESET><GREEN>^<RESET>t u<RED>|=<RESET><GREEN>|<RESET>v
 a,b<RESET>
 a<RED>::<RESET><GREEN>:<RESET>b
diff --git a/userdiff.c b/userdiff.c
index d9b2ba752f0..ce2a9230703 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -54,8 +54,14 @@ PATTERNS("cpp",
 	 /* functions/methods, variables, and compounds at top level */
 	 "^((::[[:space:]]*)?[A-Za-z_].*)$",
 	 /* -- */
+	 /* identifiers and keywords */
 	 "[a-zA-Z_][a-zA-Z0-9_]*"
-	 "|[-+0-9.e]+[fFlL]?|0[xXbB]?[0-9a-fA-F]+[lLuU]*"
+	 /* decimal and octal integers as well as floatingpoint numbers */
+	 "|[0-9][0-9.]*([Ee][-+]?[0-9]+)?[fFlLuU]*"
+	 /* hexadecimal and binary integers */
+	 "|0[xXbB][0-9a-fA-F]+[lLuU]*"
+	 /* floatingpoint numbers that begin with a decimal point */
+	 "|\\.[0-9]+([Ee][-+]?[0-9]+)?[fFlL]?"
 	 "|[-+*/<>%&^|=!]=|--|\\+\\+|<<=?|>>=?|&&|\\|\\||::|->\\*?|\\.\\*"),
 PATTERNS("csharp",
 	 /* Keywords */
-- 
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