What Makes Some C Stream Manipulators 'Sticky' While Others Are Not?

Manipulators with 'Sticky' Behavior

When utilizing manipulators in C for stream formatting, it's crucial to understand their behavior, especially regarding "stickiness." In this article, we'll explore why certain manipulators are considered "sticky," as well as their differences and potential impacts on code.

Why is std::setw() Unusually Handled?

std::setw(), a manipulator used for setting the field width, is notable for its "transient" behavior. Unlike other manipulators, its effects are not persistent for subsequent insertions, requiring explicit adjustment unless desired.

Are Other Manipulators Sticky?

The majority of manipulators indeed exhibit stickiness. Manipulators that return objects, such as:

• setiosflags
• resetiosflags
• setbase
• setfill
• setprecision

are inherently sticky, modifying the stream's state for all subsequent insertions.

Conversely, manipulators that return the stream object itself, like:

• boolalpha/noboolalpha
• showbase/noshowbase
• showpoint/noshowpoint
• showpos/noshowpos
• skipws/noskipws
• unitbuf/nounitbuf
• uppercase/nouppercase

are considered permanent and remain in effect until altered.

Distinguishing std::ios_base::width() and std::setw()

std::ios_base::width() is a method of the std::ios_base class, which represents the stream's base settings. Unlike std::setw(), it persists until explicitly reset. This distinction ensures that formatted output operations, which often use width settings, can be properly controlled.

Documentation and Resources

For a comprehensive overview of manipulator behavior, refer to the documentation for your specific implementation. Additionally, community forums and resources provide valuable insights and code examples.

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