SWI-Prolog -- json

Availability::- use_module(library(http/json)).

[det]json_write(+Stream, +Term, +Options)

Write a JSON term to Stream. The JSON object is of the same format as produced by json_read/2, though we allow for some more flexibility with regard to pairs in objects. All of Name=Value, Name-Value and Name(Value) produce the same output. In addition to the options recognised by json_read/3, we process the following options are recognised:

width(+Width): Width in which we try to format the result. Too long lines switch from horizontal to vertical layout for better readability. If performance is critical and human readability is not an issue use Width = 0, which causes a single-line output.
step(+Step): Indentation increnment for next level. Default is 2.
tab(+TabDistance): Distance between tab-stops. If equal to Step, layout is generated with one tab per level.