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Heads up!

When writing conditions, be sure to use floating-point numbers. For example, use "== 8.0" instead of "== 8".

Name	Type	Description
`formula`	`string`	A formula of pre-defined variables to be evaluated.
`condition`	`string`	A binary condition upon which `formula` will trigger an alert.

metric enforces arbitrary formulas based on pre-defined, built-in variables.

yaml
extends: metric
message: 'Try to keep the Flesch-Kincaid grade level (%s) below 8.'
link: |
  https://en.wikipedia.org/wiki/Flesch%E2%80%93Kincaid_readability_tests

formula: |
  (0.39 * (words / sentences)) + (11.8 * (syllables / words)) - 15.59

condition: '> 8.0'

Variables

The table below summarizes all available variables:

Variable	Description
`blockquote`	The number of `blockquote` tags.
`characters`	The number of characters.
`complex_words`	The number of polysyllabic words without common suffixes (`es`, `ed`, `ing`, …).
`heading.h{n}`	The number of headings at the specified level (for example, `heading.h1`).
`list`	The number of `ol` and `ul` tags.
`long_words`	The number of words with more than 6 characters.
`paragraphs`	The number of paragraphs.
`polysyllabic_words`	The number of words with more than 2 syllables.
`pre`	The number of `pre` tags.
`sentences`	The number of sentences.
`syllables`	The number of syllables.
`words`	The number of words.

Since the pre-defined variables are calculated using the entire document, all metric-based rules are summary-scoped.

Operators

In addition to using the variables listed above, a formula may also use the following operators:

Operator	Description
`+`	Addition
`-`	Subtraction
`*`	Multiplication
`/`	Division
`math.sqrt(x)`	Square root of `x`
`math.abs(x)`	Absolute value of `x`

A condition may use one of >, <, ==, >=, and <=.

message

The result of a formula will be compared to its condition and inserted into its message format specifier (%s).