Difference between revisions of "DEFSNG"

From QB64 Wiki
Jump to navigation Jump to search
imported>Clippy
m
m (Text replacement - "==Legacy support==" to "{{PageLegacySupport}}")
 
(8 intermediate revisions by 3 users not shown)
Line 1: Line 1:
The '''DEFSNG''' statement defines all designated undefined variables AS [[SINGLE]] variables.  
+
The [[DEFSNG]] statement defines all variables with names starting with the specified letter (or letter range) AS [[SINGLE]] variables.
 +
 
 +
 
 +
{{PageLegacySupport}}
 +
* '''DEF''' statements ([[DEFDBL]], [[DEFSNG]], [[DEFLNG]], [[DEFINT]], [[DEFSTR]]) were used when storage space was a concern in older computers, as their usage could save up typing. Instead of {{InlineCode}}'''DIM a AS SINGLE, a2 AS SINGLE, a3 AS SINGLE'''{{InlineCodeEnd}}, simply having {{InlineCode}}'''DEFSNG A'''{{InlineCodeEnd}} in the code before using variables starting with letter '''A''' would do the same job.
 +
* '''For clarity, it is recommended to declare variables with meaningful names'''.
  
  
 
{{PageSyntax}}
 
{{PageSyntax}}
:: DEFSNG firstletters
+
: [[DEFSNG]] {{Parameter|letter}}[-{{Parameter|range}}], {{Parameter|letter2}}[-{{Parameter|range2}}], [...]
 +
 
 +
 
 +
{{PageDescription}}
 +
* Undeclared variables with no type suffix are of type [[SINGLE]] by default.
 +
* {{Parameter|letter}} (or {{Parameter|range}}) can be from A-Z or any other range, like '''G-M'''.
 +
* You can also use commas for specific undefined variable first letters.
 +
* Variables [[DIM]]ensioned as another variable type or that use type suffixes are not affected by [[DEFSNG]].
 +
* [[DEFSNG]] sets the [[Variable Types|type]] of all variable names with the starting letter(s) or letter ranges when encountered in the progression of the program (even in conditional statement blocks not executed and subsequent [[SUB]] procedures).
 +
* '''Warning: QBasic keyword names cannot be used as numerical variable names with or without the type suffix.'''
  
  
 +
{{PageQBasic}}
 +
* QBasic's IDE would add DEF statements before any [[SUB]] or [[FUNCTION]]. QB64 (like QBasic) will change all variable types in subsequent sub-procedures to that default variable type without giving a [[ERROR Codes|"Parameter Type Mismatch"]] warning or adding DEF statement to subsequent procedures. If you do not want that to occur, either remove that DEF statement or add the proper DEF type statements to subsequent procedures. May also affect [[$INCLUDE]] procedures.
  
* The variable first letters can be from A-Z or any other range.
 
* You can also use commas for specific untyped variable first letters.
 
* Variables [[DIM]]ensioned as another variable type or that use type suffixes are not defined otherwise.
 
* DEFSNG is normally the Qbasic default assignment for undefined variables anyhow.
 
* '''Qbasic's IDE may add DEF statements before any [[SUB]] or [[FUNCTION]]. QB64(like QB) will change all variable types in subsequent sub-procedures to that default variable type without giving a [[ERROR Codes|"Parameter Type Mismatch"]] warning or adding the proper DEF statement to subsequent procedures! If you do not want that to occur, either remove that DEF statement or add the proper DEF type statements to subsequent procedures. May also affect [[$INCLUDE]] procedures!'''
 
* '''Warning: Qbasic keyword names cannot be used as numerical variable names with or without the type suffix!'''
 
  
 +
{{PageExamples}}
 +
{{CodeStart}}
 +
{{Cl|DEFSNG}} A, F-H, M
  
''Example:'' DEFSNG A-D, S
+
'With the above, all variables with names starting with A, F, G, H and M
 +
'will be of type SINGLE, unless they have a type suffix
 +
'indicating another type or they are {{Cl|DIM|dimensioned}} differently
 +
{{CodeEnd}}
  
  
''See also:''
+
{{PageSeeAlso}}
* [[DEFINT]], [[DEFDBL]], [[DEFLNG]], [[DEFSTR]]
+
* [[DEFDBL]], [[DEFLNG]], [[DEFINT]], [[DEFSTR]]
 
* [[_DEFINE]]
 
* [[_DEFINE]]
  
  
 
{{PageNavigation}}
 
{{PageNavigation}}

Latest revision as of 18:46, 15 February 2021

The DEFSNG statement defines all variables with names starting with the specified letter (or letter range) AS SINGLE variables.


Legacy support

  • DEF statements (DEFDBL, DEFSNG, DEFLNG, DEFINT, DEFSTR) were used when storage space was a concern in older computers, as their usage could save up typing. Instead of DIM a AS SINGLE, a2 AS SINGLE, a3 AS SINGLE, simply having DEFSNG A in the code before using variables starting with letter A would do the same job.
  • For clarity, it is recommended to declare variables with meaningful names.


Syntax

DEFSNG letter[-range], letter2[-range2], [...]


Description

  • Undeclared variables with no type suffix are of type SINGLE by default.
  • letter (or range) can be from A-Z or any other range, like G-M.
  • You can also use commas for specific undefined variable first letters.
  • Variables DIMensioned as another variable type or that use type suffixes are not affected by DEFSNG.
  • DEFSNG sets the type of all variable names with the starting letter(s) or letter ranges when encountered in the progression of the program (even in conditional statement blocks not executed and subsequent SUB procedures).
  • Warning: QBasic keyword names cannot be used as numerical variable names with or without the type suffix.


QBasic/QuickBASIC

  • QBasic's IDE would add DEF statements before any SUB or FUNCTION. QB64 (like QBasic) will change all variable types in subsequent sub-procedures to that default variable type without giving a "Parameter Type Mismatch" warning or adding DEF statement to subsequent procedures. If you do not want that to occur, either remove that DEF statement or add the proper DEF type statements to subsequent procedures. May also affect $INCLUDE procedures.


Examples

DEFSNG A, F-H, M 'With the above, all variables with names starting with A, F, G, H and M 'will be of type SINGLE, unless they have a type suffix 'indicating another type or they are dimensioned differently


See also



Navigation:
Keyword Reference - Alphabetical
Keyword Reference - By Usage
Main Wiki Page