Built-in Functions

A few functions are predefined, meaning you don’t have to include any packageto get access to them. lists them all.⁶

Pre-defined functions in Go.

These built-in functions are documented in the builtin pseudo package that is included in recent Go releases. Let’s go over thesefunctions briefly.

• close
• is used in channel communication. It closes a channel. We’ll learn more about this in .
• delete
• is used for deleting entries in maps.
• len and cap
• are used on a number of different types, len isused to return the lengths of strings, maps, slices, andarrays. In the next section we’ll look at slices,arrays and the function cap.
• new
• is used for allocating memory for user defineddata types. See .
• make
• is used for allocating memory for built-intypes (maps, slices, and channels). See .
• copy, append
• copy is for copying slices. And append is for concatenating slices. See in this chapter.
• panic, recover
• are used for an exception mechanism. See for more.
• print, println
• are low level printing functions that can be used without reverting to thefmt package. These are mainly used for debugging.built-in,println)
• complex, real, imag
• all deal with complex numbers. We will not use complex numbers in this book.