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json

JavaScript Object Notation (JSON)

Description

JSON is a structured data-type within Murex. It is the standard format for all structured data within Murex however other formats such as YAML, TOML and CSV are equally first class citizens.

Examples

Example JSON document taken from Wikipedia

{
  "firstName": "John",
  "lastName": "Smith",
  "isAlive": true,
  "age": 27,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021-3100"
  },
  "phoneNumbers": [
    {
      "type": "home",
      "number": "212 555-1234"
    },
    {
      "type": "office",
      "number": "646 555-4567"
    },
    {
      "type": "mobile",
      "number": "123 456-7890"
    }
  ],
  "children": [],
  "spouse": null
}

Detail

Tips when writing JSON inside for loops

One of the drawbacks (or maybe advantages, depending on your perspective) of JSON is that parsers generally expect a complete file for processing in that the JSON specification requires closing tags for every opening tag. This means it’s not always suitable for streaming. For example

» ja [1..3] -> foreach i { out ({ "$i": $i }) }
{ "1": 1 }
{ "2": 2 }
{ "3": 3 }

What does this even mean and how can you build a JSON file up sequentially?

One answer if to write the output in a streaming file format and convert back to JSON

» ja [1..3] -> foreach i { out (- "$i": $i) }
- "1": 1
- "2": 2
- "3": 3

» ja [1..3] -> foreach i { out (- "$i": $i) } -> cast yaml -> format json
[
    {
        "1": 1
    },
    {
        "2": 2
    },
    {
        "3": 3
    }
]

What if I’m returning an object rather than writing one?

The problem with building JSON structures from existing structures is that you can quickly end up with invalid JSON due to the specifications strict use of commas.

For example in the code below, each item block is it’s own object and there are no [ ... ] encapsulating them to denote it is an array of objects, nor are the objects terminated by a comma.

» config -> [ shell ] -> formap k v { $v -> alter /Foo Bar }
{
    "Data-Type": "bool",
    "Default": true,
    "Description": "Display the interactive shell's hint text helper. Please note, even when this is disabled, it will still appear when used for regexp searches and other readline-specific functions",
    "Dynamic": false,
    "Foo": "Bar",
    "Global": true,
    "Value": true
}
{
    "Data-Type": "block",
    "Default": "{ progress $PID }",
    "Description": "Murex function to execute when an `exec` process is stopped",
    "Dynamic": false,
    "Foo": "Bar",
    "Global": true,
    "Value": "{ progress $PID }"
}
{
    "Data-Type": "bool",
    "Default": true,
    "Description": "ANSI escape sequences in Murex builtins to highlight syntax errors, history completions, {SGR} variables, etc",
    "Dynamic": false,
    "Foo": "Bar",
    "Global": true,
    "Value": true
}
...

Luckily JSON also has it’s own streaming format: JSON lines (jsonl). We can cast this output as jsonl then format it back into valid JSON:

» config -> [ shell ] -> formap k v { $v -> alter /Foo Bar } -> cast jsonl -> format json
[
    {
        "Data-Type": "bool",
        "Default": true,
        "Description": "Write shell history (interactive shell) to disk",
        "Dynamic": false,
        "Foo": "Bar",
        "Global": true,
        "Value": true
    },
    {
        "Data-Type": "int",
        "Default": 4,
        "Description": "Maximum number of lines with auto-completion suggestions to display",
        "Dynamic": false,
        "Foo": "Bar",
        "Global": true,
        "Value": "6"
    },
    {
        "Data-Type": "bool",
        "Default": true,
        "Description": "Display some status information about the stop process when ctrl+z is pressed (conceptually similar to ctrl+t / SIGINFO on some BSDs)",
        "Dynamic": false,
        "Foo": "Bar",
        "Global": true,
        "Value": true
    },
...

foreach will automatically cast it’s output as jsonl if it’s stdin type is json

» ja [Tom,Dick,Sally] -> foreach name { out Hello $name }
Hello Tom
Hello Dick
Hello Sally

» ja [Tom,Dick,Sally] -> foreach name { out Hello $name } -> debug -> [[ /Data-Type/Murex ]]
jsonl

» ja [Tom,Dick,Sally] -> foreach name { out Hello $name } -> format json
[
    "Hello Tom",
    "Hello Dick",
    "Hello Sally"
]

Default Associations

• Extension: json
• MIME: application/json
• MIME: application/x-json
• MIME: text/json
• MIME: text/x-json

Supported Hooks

• Marshal() Writes minified JSON when no TTY detected and human readable JSON when stdout is a TTY
• ReadArray() Works with JSON arrays. Maps are converted into arrays
• ReadArrayWithType() Works with JSON arrays. Maps are converted into arrays. Elements data-type in Murex mirrors the JSON type of the element
• ReadIndex() Works against all properties in JSON
• ReadMap() Works with JSON maps
• ReadNotIndex() Works against all properties in JSON
• Unmarshal() Supported
• WriteArray() Works with JSON arrays

See Also

• Define Type (cast): Alters the data-type of the previous function without altering its output
• Get Nested Element ([[ Element ]]): Outputs an element from a nested structure
• Open File (open): Open a file with a preferred handler
• Prettify JSON: Prettifies JSON to make it human readable
• Reformat Data type (format): Reformat one data-type into another data-type
• Shell Runtime (runtime): Returns runtime information on the internal state of Murex
• hcl: HashiCorp Configuration Language (HCL)
• jsonc: Concatenated JSON
• jsonl: JSON Lines
• toml: Tom’s Obvious, Minimal Language (TOML)
• yaml: YAML Ain’t Markup Language (YAML)
• index: Outputs an element from an array, map or table
• mxjson: Murex-flavoured JSON (deprecated)

Read more about type hooks

• ReadIndex() (type): Data type handler for the index, [, builtin
• ReadNotIndex() (type): Data type handler for the bang-prefixed index, ![, builtin
• ReadArray() (type): Read from a data type one array element at a time
• WriteArray() (type): Write a data type, one array element at a time
• ReadMap() (type): Treat data type as a key/value structure and read its contents
• Marshal() (type): Converts structured memory into a structured file format (eg for stdio)
• Unmarshal() (type): Converts a structured file format into structured memory

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This document was generated from builtins/types/json/json_doc.yaml.