Table of Contents

1 library(yaml): Process YAML data

This module parses YAML serialized data into a Prolog term with structure that is compatible with the JSON library. This library is a wrapper around the C library libyaml. This library forms the basis of the YAML support in several languages and thus guarantees compatibility of our YAML support with other languages.

[det]yaml_read(+Input, -DOM)

Parse Input to a YAML DOM. The DOM representation uses the following mapping:

• A YAML sequence is mapped to a Prolog List.
• A YAML mapping is mapped to a Prolog dict.
• Untagged scalars follow the implicit tag rules defined by YAML, providing numbers (int, float and special floats), null and the booleans true and false. Other untagged values are returned as a Prolog string. Tagged values are returned as tag(Tag, String) which is processed by yalm_tagged/3. This internal predicate calls the user hook yaml:tagged/3 with the same arguments and, if the hook fails, provides the following defaults:
  • !!binary converts the Base64 to a string of bytes.
  • !!str explicitly keeps a string
  • !!null translates "null" to null
  • !!bool translates to true and false
  • !!int translates to an integer
  • !!float translates to a float
  • Anything else is returned as tag(Tag, String)

Input

is one of (1) a stream, (2) a term string(Data) or (3) a file name.

bug

YAML defines that floats do not require a digit after the decimal dot. We use the Prolog parser which does require the decimal dot to be followed by at least one digit. Because the YAML spec intends to match JSON which does require a digit, we ignore this incompatibility, expecting it will be addressed in the next YAML version.

[det]yaml_write(+Out:stream, +DOM)

[det]yaml_write(+Out:stream, +DOM, +Options)

Emit a YAML DOM object as a serialized YAML document to the stream Out. Options processed are:

canonical(+Boolean)

Use canonical representation. Default is false.

unicode(+Boolean)

Use unicode Default is true.

implicit(+Boolean)

Use implicit or explicit representation. Currently only affects the opening and closing the document. Default is true. Use false for embedded documents.

factorize(+Boolean)

If true, minimize the term by factoring out common structures and use &anchor and *anchor. Factorization is always used if DOM is a cyclic term.

[semidet,multifile]tagged(+Tag, ?String, ?Value)

Hook that allows convering !!tag values to be decoded or encoded.

Index

?

tagged/3

yaml_read/2

yaml_write/2

yaml_write/3