11.3.3 Operator Line-Up Functions

The line-up functions here calculate the indentation for lines which start with an operator, by lining it up with something on the previous line.

Function: c-lineup-argcont

Line up a continued argument. E.g:

foo (xyz, aaa + bbb + ccc
          + ddd + eee + fff);  <- c-lineup-argcont

Only continuation lines like this are touched, nil is returned on lines which are the start of an argument.

Within a gcc asm block, : is recognized as an argument separator, but of course only between operand specifications, not in the expressions for the operands.

Works with:  arglist-cont, arglist-cont-nonempty.

Function: c-lineup-arglist-operators

Line up lines starting with an infix operator under the open paren. Return nil on lines that don’t start with an operator, to leave those cases to other line-up functions. Example:

if (  x < 10
   || at_limit (x,     <- c-lineup-arglist-operators
                list)  <- c-lineup-arglist-operators returns nil
   )

Since this function doesn’t do anything for lines without an infix operator you typically want to use it together with some other lineup settings, e.g. as follows (the arglist-close setting is just a suggestion to get a consistent style):

(c-set-offset 'arglist-cont
              '(c-lineup-arglist-operators 0))
(c-set-offset 'arglist-cont-nonempty
              '(c-lineup-arglist-operators c-lineup-arglist))
(c-set-offset 'arglist-close
              '(c-lineup-arglist-close-under-paren))

Works with:  arglist-cont, arglist-cont-nonempty.

Function: c-lineup-assignments

Line up the current line after the assignment operator on the first line in the statement. If there isn’t any, return nil to allow stacking with other line-up functions. If the current line contains an assignment operator too, try to align it with the first one.

Works with:  topmost-intro-cont, statement-cont, arglist-cont, arglist-cont-nonempty.

Function: c-lineup-math

Like c-lineup-assignments but indent with c-basic-offset if no assignment operator was found on the first line. I.e. this function is the same as specifying a list (c-lineup-assignments +). It’s provided for compatibility with old configurations.

Works with:  topmost-intro-cont, statement-cont, arglist-cont, arglist-cont-nonempty.

Function: c-lineup-ternary-bodies

Line up true and false branches of a ternary operator (i.e. ?:). More precisely, if the line starts with a colon which is a part of a said operator, align it with the corresponding question mark. For example:

return arg % 2 == 0 ? arg / 2
                    : (3 * arg + 1);    <- c-lineup-ternary-bodies

Works with:  arglist-cont, arglist-cont-nonempty and statement-cont.

Function: c-lineup-cascaded-calls

Line up “cascaded calls” under each other. If the line begins with -> or . and the preceding line ends with one or more function calls preceded by the same token, then the arrow is lined up with the first of those tokens. E.g:

r = proc->add(17)->add(18)
        ->add(19) +         <- c-lineup-cascaded-calls
  offset;                   <- c-lineup-cascaded-calls (inactive)

In any other situation nil is returned to allow use in list expressions.

Works with:  topmost-intro-cont, statement-cont, arglist-cont, arglist-cont-nonempty.

Function: c-lineup-streamop

Line up C++ stream operators (i.e. ‘<<’ and ‘>>’).

Works with:  stream-op.

Function: c-lineup-string-cont

Line up a continued string under the one it continues. A continued string in this sense is where a string literal follows directly after another one. E.g:

result = prefix + "A message "
                  "string.";    <- c-lineup-string-cont

nil is returned in other situations, to allow stacking with other lineup functions.

Works with:  topmost-intro-cont, statement-cont, arglist-cont, arglist-cont-nonempty.