&DOWHILE

&DOWHILE builds a conditional loop with the test at the top.

&DOWHILE expression [ AND | OR expression .... ]

The &DOWHILE loop is executed repetitively while the conditions specified in the expressions are true.

If initially false, the loop is not executed.

When the test fails, execution continues past the &DOEND statement paired with the &DOWHILE statement.

Operands:

expression

This expression acts as the test for the &DOWHILE condition and is evaluated at the top of the loop:

If true the &DOWHILE loop executes.
If the expression is false, execution continues past the associated &DOEND statement.

Compounded expressions is used, joined with AND, or OR operators, but parentheses cannot be used.

Examples: &DOWHILE

&DOWHILE &A << 10  AND &A >> &B  
  &B = &B + 2  
  &A = &A + 1
&DOEND

This simple loop is repeated while &A is less than 10, and while &A is greater than &B.

&LINECNT = 1
&GOSUB .GETDATALINE
&DOWHILE &LINECNT <= 20 AND &RETCODE EQ 0
   &LINE&LINECNT = &DATALINE
   &LINECNT = &LINECNT + 1
   &GOSUB .GETDATALINE
&DOEND
&IF &LINECNT <= 20 &THEN +
   &LINE&LINECNT = &STR **END**

This example sets up the variables &LINE1 to &LINE20 to data returned from the .GETDATALINE subroutine (which can read records from a file, for example). The loop is terminated by either reaching the end of the data available (that is, the routine .GETDATALINE returns a non-zero return code) or when all the variables have been set (that is, when all the variables have been set (that is, when &LINECNT reaches a value of 21). These variables can then be displayed on a panel.

Notes:

&DOWHILE groups must be terminated by an &DOEND statement, that is, &DO and &DOEND statements must be paired. Unbalanced pairs cause syntax errors at load time.

&LOOPCTL is provided to control runaway looping. Iterations of loops during &DOWHILE and &DOUNTIL processing are included in &LOOPCTL calculations.

More information:

&DO

&DOUNTIL