Solving Math Expressions

Solving Math Expressions on Github

/spec/workflow-yaml/foreach/

This example shows how we can iterate over data using the ForEach state. Which executes an action that solves a math expression. The flow data input are the expressions you want to solve as a string array.

The example demonstrates the use of an action isolate to solve a number of mathematical expressions using a foreach state. For each expression in the input array, the isolate will be run once.

Solver Flow

# Example Input:
# {
#  "expressions": [
#    "4+10",
#    "15-14",
#    "100*3",
#    "200/2"
#  ]
# }
#
# Example Output:
# The results of this foreach loop will be a json array of strings that have the solved answers.
# {
#   "solved": [
#     "14",
#     "1",
#     "300",
#     "100"
#   ]
# }

direktiv_api: workflow/v1

description: |
  Executes an action that solves a math expression. 
  The workflow data input are the expressions you want to solve as a string array.

functions:
- id: solve-math-expression
  image: direktiv/bash:dev
  type: knative-workflow

states:
  - id: validate-input
    type: validate
    schema:
      type: object
      required:
      - expressions
      properties:
        expressions:
          type: array
          description: expressions to solve
          title: Expressions
          items:
            type: string
    transition: solve

  #
  # Execute solve action.
  #
  - id: solve
    type: foreach
    array: 'jq([.expressions[] | { expression: . }])'
    action:
      function: solve-math-expression
      input: 
        commands: 
        - command: bash -c "echo $((jq(.expression)))"
    transform: 'jq({ solved: [.return[] | .bash[0].result ] })'

Input

{
  "expressions": [
    "4+10",
    "15-14",
    "100*3",
    "200/2"
  ]
}

The results of this foreach loop will be a json array of strings that have the solved answers.

Output

{
  "solved": [
    "14",
    "1",
    "300",
    "100"
  ]
}

Note: The array for a foreach state must be passed as an array of objects. This is why to iterate over the expressions string array, we must pipe it and construct a new array of objects using [.expressions[] | { expression: . }].

jq: .expressions

[
  "4+10",
  "15-14",
  "100*3",
  "200/2"
]

jq: [.expressions[] | { expression: . }]

[
  {
    "expression": "4+10"
  },
  {
    "expression": "15-14"
  },
  {
    "expression": "100*3"
  },
  {
    "expression": "200/2"
  }
]