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Standard Libraries

Gno comes with a set of standard libraries which are included to ease development and provide extended functionality to the language. These include:

  • standard libraries as we know them in classic Go, i.e. encoding/binary, strings, testing, etc.
  • a special std package, which contains types, interfaces, and APIs created to handle blockchain-related functionality.

Standard libraries differ from on-chain packages in terms of their import path structure. Unlike on-chain packages, standard libraries do not incorporate a domain-like format at the beginning of their import path. For example:

  • import "encoding/binary" refers to a standard library
  • import "gno.land/p/demo/avl" refers to an on-chain package.

To see concrete implementation details & API references, see the reference section.

Accessing documentation​

Apart from the official documentation you are currently reading, you can also access documentation for the standard libraries in several other different ways. You can obtain a list of all the available standard libraries with the following commands:

$ cd gnovm/stdlibs # go to correct directory

$ find -type d
./testing
./math
./crypto
./crypto/chacha20
./crypto/chacha20/chacha
./crypto/chacha20/rand
./crypto/sha256
./crypto/cipher
...

All the packages have automatically generated documentation through the use of the gno doc command, which has similar functionality and features to go doc:

$ gno doc encoding/binary
package binary // import "encoding/binary"

Package binary implements simple translation between numbers and byte sequences
and encoding and decoding of varints.

[...]

var BigEndian bigEndian
var LittleEndian littleEndian
type AppendByteOrder interface{ ... }
type ByteOrder interface{ ... }
$ gno doc -u -src encoding/binary littleEndian.AppendUint16
package binary // import "encoding/binary"

func (littleEndian) AppendUint16(b []byte, v uint16) []byte {
        return append(b,
                byte(v),
                byte(v>>8),
        )
}

gno doc will work automatically when used within the Gno repository or any repository which has a go.mod dependency on github.com/gnolang/gno.

Another alternative is setting your environment variable GNOROOT to point to where you cloned the Gno repository.

export GNOROOT=$HOME/gno