README.md in csv_decision-0.0.3 vs README.md in csv_decision-0.0.4
- old
+ new
@@ -2,41 +2,43 @@
============
[](https://badge.fury.io/rb/csv_decision)
[](https://travis-ci.org/bpvickers/csv_decision)
[](https://coveralls.io/github/bpvickers/csv_decision?branch=master)
-<a href="https://codeclimate.com/github/bpvickers/csv_decision/maintainability"><img src="https://api.codeclimate.com/v1/badges/466a6c52e8f6a3840967/maintainability" /></a>
+[](https://codeclimate.com/github/bpvickers/csv_decision/maintainability)
+[](#license)
### CSV based Ruby decision tables (a lightweight Hash transformation gem)
`csv_decision` is a RubyGem for CSV (comma separated values) based
[decision tables](https://en.wikipedia.org/wiki/Decision_table).
It accepts decision tables implemented as a
[CSV file](https://en.wikipedia.org/wiki/Comma-separated_values),
which can then be used to execute complex conditional logic against an input hash,
producing a decision as an output hash.
- ### `csv_decision` features
+ ### CSV Decision features
* Fast decision-time performance (see `benchmark.rb`).
- * In addition to simple string matching, can use regular expressions,
- numeric comparisons and Ruby-style ranges.
+ * In addition to simple string matching, can match common Ruby constants,
+ regular expressions, numeric comparisons and Ruby-style ranges.
+ * Can use column symbols in comparisons for guard conditions -- e.g., > :column.
* Accepts data as a file, CSV string or an array of arrays. (For safety all input data is
force encoded to UTF-8, and non-ascii strings are converted to empty strings.)
* All CSV cells are parsed for correctness, and helpful error messages generated for bad
inputs.
* Either returns the first matching row as a hash, or accumulates all matches as an
array of hashes.
### Planned features
- `csv_decision` is currently a work in progress, and will be enhanced to support
+ `csv_decision` is still a work in progress, and will be enhanced to support
the following features:
* Input columns may be indexed for faster lookup performance.
* May use functions in the output columns to formulate the final decision.
* Input hash values may be conditionally defaulted using a constant or a function call
* Use of column symbol references or built-in guard functions in the input
columns for matching.
- * Output columns may used interpolated strings referencing column symbols.
+ * Output columns may use interpolated strings referencing column symbols.
* May be extended with user-defined Ruby functions for tailored logic.
* Can use post-match guard conditions to filter the results of multi-row
decision output.
### Why use `csv_decision`?
@@ -147,30 +149,61 @@
`lib/csv_decision/parse.rb` and `lib/csv_decision/table.rb`.
### Constants other than strings
Although `csv_decision` is string oriented, it does recognise other types of constant
present in the input hash. Specifically, the following classes are recognized:
- `Integer`, `BigDecimal` and `NilClass`.
+ `Integer`, `BigDecimal`, `NilClass`, `TrueClass` and `FalseClass`.
This is accomplished by prefixing the value with one of the operators `=`, `==` or `:=`.
(The syntax is intentionally lax.)
For example:
```ruby
data = <<~DATA
- in :constant, out :type
- :=nil, NilClass
- ==false, FALSE
- =true, TRUE
- = 0, Zero
- :=100.0, 100%
+ in :constant, out :value
+ :=nil, :=nil
+ ==false, ==false
+ =true, =true
+ = 0, = 0
+ :=100.0, :=100.0
DATA
table = CSVDecision.parse(data)
- table.decide(constant: nil) # returns type: 'NilClass'
- table.decide(constant: 0) # returns type: 'Zero'
- table.decide(constant: BigDecimal.new('100.0')) # returns type: '100%'
+ table.decide(constant: nil) # returns value: nil
+ table.decide(constant: 0) # returns value: 0
+ table.decide(constant: BigDecimal('100.0')) # returns value: BigDecimal('100.0')
```
+
+ ### Column header symbols
+ All input and output column names are symbolized, and can be used to form simple
+ expressions that refer to values in the input hash.
+
+ For example:
+ ```ruby
+ data = <<~DATA
+ in :node, in :parent, out :top?
+ , == :node, yes
+ , , no
+ DATA
+
+ table = CSVDecision.parse(data)
+ table.decide(node: 0, parent: 0) # returns top?: 'yes'
+ table.decide(node: 1, parent: 0) # returns top?: 'no'
+ ```
+
+ Note that there is no need to include an input column for `:node` in the decision
+ table - it just needs to be present in the input hash. Also, `== :node` can be
+ shortened to just `:node`, so the above decision table may be simplified to:
+
+ ```ruby
+ data = <<~DATA
+ in :parent, out :top?
+ :node, yes
+ , no
+ DATA
+ ```
+ These comparison operators are also supported: `!=`, `>`, `>=`, `<`, `<=`.
+ For more simple examples see `spec/csv_decision/examples_spec.rb`.
### Testing
`csv_decision` includes thorough [RSpec](http://rspec.info) tests: