28.6.4.3 Using loop structures

Mif2Go 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

“While” loops

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).

“Until” loops

Because “until” is really the same as “while not”, the <$_while> runaway-prevention limit also applies to <$_until> loops:

[HtmlOptions]

WhileMax=128

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).

“Repeat” loops

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>.

Nest loops

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>

Move around within loops

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.

---

> 28 Working with macros > 28.6 Using expressions in macros > 28.6.4 Using control structures in expressions > 28.6.4.3 Using loop structures