YAML basics¶

The YAML format is the only input format supported by exaStamp. This page recalls the basics of plain YAML. exaStamp and the underlying onika/exaNBody platform add a few extensions on top of it (reserved keys, file inclusion, component overriding, etc.), which are described in YAML extensions.

Basic types¶

YAML is a human-readable data serialization often used for writing configuration files and in applications where data is being stored or transmitted by/between operators. Recursive definition of YAML document is pretty simple and a YAML document usually contains three types of elements:

• scalars: text, number, boolean
• lists: an ensemble of ordered elements
• dictionaries: an ensemble, ordered or not, of tuples each with a key and an associated value

For more information about the YAML framework, please visit the following links:

• YAML Tutorials
• YAML Online Parser
• YAML Wiki

Below are some examples of scalar, list or dictionary definitions in YAML format.

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# Scalar definition examples
val: "text only"
val: 3.5
val: true

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# List definition examples
list: ["list", "with", 5, true, "elements"]
list:
  - "list"
  - "with"
  - 5
  - true
  - elements

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# Dictionary definition examples
dict: {A: "value", B: 3, C: false}
dict:
  A: "value"
  B: 3
  C: false

Combining types¶

In addition, you can combine multiple types (scalar, list, dictionary):

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# Multiple types combination in a dictionary
dictA:   
  key1: { A: "value", B: 3 }
  key2: [ "aaa", "bbb" ]
  key3: 4.67
  key4:
    A: [ 5, 6 ]
    B: { X: 1, Y: 2 }

# Alternative format  
dictA: { key1: { A: "value", B: 3 }, key2: [ "aaa", "bbb" ], key3: 4.67, key4: { A: [ 5, 6 ], B: { X: 1, Y: 2 } } }

Here, key1 is bound to a value of type dictionary, key2 is bound to a value of type list, key3 is bound to a value of type scalar, key4 is bound to a value of type dictionary.