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YAML Overview

Before writing CloudSlang code it helps to have a good working knowledge of YAML. The following is a brief overview of some of the YAML specification. See the full YAML specification for more information.

Whitespace

Unlike many programming, markup, and data serialization languages, whitespace is syntactically significant. Indentation is used to denote scope and is always achieved using spaces. Never use tabs.

Example: a CloudSlang task (in this case named divider) contains do, publish and navigate keys

- divider:
    do:
      divide:
        - dividend: input1
        - divisor: input2
    publish:
      - answer: quotient
    navigate:
      ILLEGAL: FAILURE
      SUCCESS: printer

Lists

Lists are denoted with a hypen (-) and a space preceding each list item.

Example: a CloudSlang flow's possible results are defined using a list mapped to the results key

results:
  - ILLEGAL
  - SUCCESS

Maps

Maps are denoted use a colon (:) and a space between each key value pair.

Example: a CloudSlang task's navigate key is mapped to a mapping of results and their targets

navigate:
  ILLEGAL: FAILURE
  SUCCESS: printer

Strings

Strings can be denoted in several ways: unquoted, single quoted and double quoted. The best method for any given string depends on whether it includes any special characters, leading or trailing whitespace, spans multiple lines, along with other factors.

Strings that span multiple lines can be written using a pipe (|) to preserve line breaks or a greater than symbol (>) where each line break will be converted to a space.

Example: a name of a CloudSlang flow is defined using the unquoted style

flow:
  name: hello_world

Example: the single or double quoted style is used in CloudSlang to pass a Python string, which is quoted using the other style, to an input parameter

- sayHi:
    do:
      print:
        - text: "'Hello, World'"

Example: the pipe is used in CloudSlang to indicate a multi-line Python script

action:
  python_script: |
    if divisor == '0':
      quotient = 'division by zero error'
    else:
      quotient = float(dividend) / float(divisor)

Comments

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