====== CATCH ======
/* Remove the comments after creating content for each section.*/

Marks the beginning of a code block to be executed if an exception happens in the main portion of a subroutine

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*/

**Implemented by:** [[:basics:Gambas:]]

**With variations:** 

**Also written as: ** 

===== Usage =====
/* For inline examples of syntax, write the keyword between '' and '' (two single quotes) */

CATCH is used in the body of a subroutine, right before its [[END]], for defining a portion of code that must be executed if an exception/error occurs somewhere in the subroutine out of a [[TRY]] block.

It is important to notice that a CATCH block in Gambas must be placed //after// an occasional [[FINALLY]] block in the subroutine. The following example is found in Gambas documentation:

<code gambas>
SUB PrintFile(FileName AS STRING)

  DIM hFile AS File
  DIM sLig AS STRING

  hFile = OPEN FileName FOR READ

  WHILE NOT EOF(hFile)
    LINE INPUT #hFile, sLig
    PRINT sLig
  WEND

FINALLY ' Always executed, even if a error is raised. Warning: FINALLY must come before CATCH!
  CLOSE #hFile

CATCH ' Executed only if there is an error
  PRINT "Cannot print file "; FileName

END
</code>

/*
==== Variations ====



===== Examples =====
*/
/*
  Below is an example of a code block, using GeSHi syntax highlighting for //gwbasic//. Other styles of interest might be
  //basic4gl//, //blitzbasic//, //freebasic//, //gambas//, //locobasic//, //purebasic//, //qbasic//, //sdlbasic//,
  //thinbasic//, //vb//, //vbnet//, //xbasic// or //zxbasic//. 

  <code gwbasic>
  10 PRINT "HELLO"
  </code>
*/



===== Comments =====
/* Origin of the keyword, opinions, history... */
At the time of this writing, CATCH seemed to be an oddity of [[:basics:gambas|Gambas]] only — alas, in most BASICs error handling is not exactly an area of excellence.

The fact that a [[FINALLY]] block must //precede// a CATCH block is counter-intuitive, and not by fortune different of every other programming language that implements "try-catch-finally" error handling. 

===== Related keywords =====
/* Keywords that are often or always used along this one */

  * [[FINALLY]]

===== Similar keywords =====
/* Keywords with the same or similar functionality found in other versions of BASIC */

  * [[TRY]]
  * [[ERROR]]
  * [[ON_ERROR|ON ERROR]]

===== In other languages... =====
/* For parallels and comparisons with other modern-day languages */
Most languages that have a //catch// statement use it as part of a //try// block. Quite often, multiple //catch// blocks can be used for treating different types of errors or exceptions. Java and PHP are some examples.

Tcl had a //catch// command long before it had //try// blocks, but it works somehow like a traditional //try//. 

===== References =====
/* If you used the ((citation)) syntax elsewhere in the text, they will appear under this section. But you can write some recommendations of books, magazines, etc */

  * https://gambaswiki.org/wiki/lang/catch , last check 2024-03-06
  * https://gambaswiki.org/wiki/cat/error , last check 2024-03-06

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