Changes: Search for a C-style for statement

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Tip 1320 Printable Monobook Previous Next

created 2006 · complexity intermediate · author QBerrt · version 5.7

Q: How to do a search that will find both of the following examples?

for (
  int i=0;
  i<3;
  i++
)

and

for ( int i=0; i<3; i++)

A: Use this pattern

\<for\>[ ^I\n]\{-0,}([ ^I\n]\{-0,}.*;[ ^I\n]\{-0,}.*;[ ^I\n]\{-0,}.*[ ^I\n]\{-0,})

Explanation:

\<for\> //Match the word "for"
[ ^I\n]\{-0,} //Match any whitespace (space " ", tab "^I", newline "\n") 0 or more times with a non-greedy search (the negative makes it non-greedy)

Why go to all this trouble instead of searching for \<for\>?

Let's say I wanted to find all places where I do a for loop against MAX_INT. I could say:

/\<for\>[ ^I\n]\{-0,}([ ^I\n]\{-0,}.*;[ ^I\n]\{-0,}.*MAX_INT.*;[ ^I\n]\{-0,}.*[ ^I\n]\{-0,})

Comments[]

Another possibility using \_, which adds newline matching to various patterns:

\<for\>\_s*(\_s*.\{-};\_s*.\{-};\_s.\{-}\_s*)

May or may not satisfy your requirement exactly, but works for the given examples.

This may suffice as well for the first 2 examples:

\<for\>\_s*(\(\_s*.*;\)\{2}\_s.*\_s*)

@@ Line 4: / Line 4: @@
 |previous=1319
 |next=1321
-|created=September 6, 2006
+|created=2006
 |complexity=intermediate
 |author=QBerrt
 |version=5.7
 |rating=0/2
+|category1=C
+|category2=C++
+|category3=Searching
 }}
 '''Q:''' How to do a search that will find both of the following examples?
@@ Line 14: / Line 17: @@
 for (
   int i=0;
-  i&lt;3;
+  i<3;
   i++
 )
@@ Line 21: / Line 24: @@
 and
 <pre>
-for ( int i=0; i&lt;3; i++)
+for ( int i=0; i<3; i++)
 </pre>
 '''A:''' Use this pattern
 <pre>
-\&lt;for\&gt;[ ^I\n]\{-0,}([ ^I\n]\{-0,}.*;[ ^I\n]\{-0,}.*;[ ^I\n]\{-0,}.*[ ^I\n]\{-0,})
+\<for\>[ ^I\n]\{-0,}([ ^I\n]\{-0,}.*;[ ^I\n]\{-0,}.*;[ ^I\n]\{-0,}.*[ ^I\n]\{-0,})
 </pre>
 Explanation:
-*<tt>\&lt;for\&gt;</tt> //Match the word "for"
+*<code>\<for\></code> //Match the word "for"
-*<tt>[ ^I\n]\{-0,}</tt> //Match any whitespace (space " ", tab "^I", newline "\n") 0 or more times with a non-greedy search (the negative makes it non-greedy)
+*<code>[ ^I\n]\{-0,}</code> //Match any whitespace (space " ", tab "^I", newline "\n") 0 or more times with a non-greedy search (the negative makes it non-greedy)
-Why go to all this trouble instead of searching for <tt>\&lt;for\&gt;</tt>?
+Why go to all this trouble instead of searching for <code>\<for\></code>?
 Let's say I wanted to find all places where I do a for loop against MAX_INT. I could say:
 <pre>
-/\&lt;for\&gt;[ ^I\n]\{-0,}([ ^I\n]\{-0,}.*;[ ^I\n]\{-0,}.*MAX_INT.*;[ ^I\n]\{-0,}.*[ ^I\n]\{-0,})
+/\<for\>[ ^I\n]\{-0,}([ ^I\n]\{-0,}.*;[ ^I\n]\{-0,}.*MAX_INT.*;[ ^I\n]\{-0,}.*[ ^I\n]\{-0,})
 </pre>
@@ Line 43: / Line 46: @@
 Another possibility using \_, which adds newline matching to various patterns:
 <pre>
-\&lt;for\&gt;\_s*(\_s*.\{-};\_s*.\{-};\_s.\{-}\_s*)
+\<for\>\_s*(\_s*.\{-};\_s*.\{-};\_s.\{-}\_s*)
 </pre>
@@ Line 51: / Line 54: @@
 This may suffice as well for the first 2 examples:
 <pre>
-\&lt;for\&gt;\_s*(\(\_s*.*;\)\{2}\_s.*\_s*)
+\<for\>\_s*(\(\_s*.*;\)\{2}\_s.*\_s*)
 </pre>
 ----
-[[Category:C]]
-[[Category:C++]]
-[[Category:Searching]]