Module parse_bif_coalesce

{:coalesce; … :}

Output the first non-empty (non-zero length) of a block list. Nothing may be displayed if all blocks are empty.

{:coalesce;
    {:;varname1:}
    {:;varname2:}
    {:;varname3:}
:}

{:coalesce;
    {:code;
        {:code; ... :}
        {:code; ... :}
        {:code; ... :}
    :}
    {:code;
        {:code; ... :}
    :}
    {:;varname:}
:}

Modifiers:

{:+coalesce; varname >> ... :}
{:^coalesce; varname >> ... :}

For more details about the “+” modifier see “modifiers”.

Modifier: ^ (upline)

Eliminates previous whitespaces, (See “unprintable” for examples.)

No flags

Nesting

Can be nested (no limit):

{:coalesce;
    {:coalesce;
        {:code; ... :}
        {:code; ... :}
        {:code; ... :}
    :}
    {:code;
        {:code; ... :}
    :}
:}

Blocks

Each block can be a single Bif, or a nested set of them:

                {:coalesce;
              .---- {:code;
              |         {:code; ... :}
    Block --> |         {:code; ... :}
              |         {:code; ... :}
              `---- :}
              .---- {:code;
    Block --> |         {:code; ... :}
              `---- :}
    Block --------> {:;varname:}
                :}

Spaces

A variable with spaces is not a zero length string, the following example will show the contents of spaces:

{:coalesce;
    {:;spaces:}
    {:code;
        Hello
    :}
:}

In reality, spaces will not be displayed, the output will be empty, since the default behavior of neutral is to ignore spaces.

If the variable with spaces was nested, then the result would be an empty block, the following will show “Hello”:

{:coalesce;
    {:code;
        {:;spaces:}
    :}
    {:code;
        Hello
    :}
:}

Unprintable Bif {:;:} is not a zero length string, the following will show nothing:

{:coalesce;
    {:code;
        {:;:}
    :}
    {:code;
        Hello
    :}
:}

Do not show anything if a condition is given:

{:coalesce;
    {:defined; varname >>
        {:;:}
    :}
    {:code;
        Hello
    :}
:}

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