DITA2Go supports “while” loops, “repeat” loops, and “until” loops:
<$_while (expr)>...<$_endwhile> loops while expr is not 0 (zero)
<$_repeat (expr)>...<$_endrepeat> loops for the count
of expr
<$_until (expr)>...<$_enduntil> loops while expr is false
For <$_while>, a runaway-prevention feature ends the loop after the maximum count specified in the following setting:
[Macros]
; WhileMax = maximum count for <$_while>, to prevent runaways;
the
; current count can be accessed using predefined macro variable
; <$$_wcount>
WhileMax=128
Predefined variable <$$_wcount> contains the loop count, starting with 1 (one).
Because “until” is really the same as “while not”, the <$_while> runaway-prevention limit also applies to <$_until> loops:
For example, a loop controlled by <$_until (0)> goes to the WhileMax limit, unless you include an effective <$_break>. Predefined variable <$$_wcount> contains the loop count, starting with 1 (one).
For <$_repeat>, the runaway-prevention limit comes into play only if the count is set to zero:
[Macros]
; RepeatMax = maximum count for <$_repeat> when value is not given,
so
; that loop continues until a <$_break condition> is met
RepeatMax=128
The current loop count is held in predefined variable <$$_count>, and the down-count starting with expr is in predefined variable <$$_dcount>.
You cannot nest a <$_while> in a <$_while>, or a <$_repeat> in a <$_repeat>, in the same macro. Nor can you nest a <$_while> in an <$_until>, or an <$_until> in a <$_while>. Instead you can call another macro to run a sub-loop. However, you can nest a <$_while> in a <$_repeat>, or a <$_repeat> in a <$_while>, and you can use one layer of <$_if> in the mix:
<$_while (expr)>
<$_if (expr)>
<$_repeat (expr)>...<$_endrepeat>
<$_else>
<$_repeat (expr)>...<$_endrepeat>
<$_endif>
<$_endwhile>
You can use <$_break> to skip to the end of the loop, and <$_continue> to jump back to the start of the next iteration. Although you can invoke these control elements in <$_if>s, it is simpler to use the following constructs:
<$_break if (expr)>
<$_continue if (expr)>
Use only a single space before each if, and a minimum of one space after each if. These constructs work even in nested <$_while> or <$_repeat> loops, where they apply to the innermost of the loops where they occur.