5.2.2.3 expr="..." attribute

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5.2.2.3 `expr="..."` attribute

For `text`, `password`, `submit`, `reset`, `hidden`, and `button` input field types the expression in the `expr` attribute is evaluated and the result is used to generate the `value` (5.2.2.11) attribute. If the result is `None` then no `value` attribute will be written.

For `radio` and `checkbox` input field types the expression in the `expr` attribute is evaluated and the result is compared with the generated `value` attribute to determine whether or not the `checked` (5.2.2.2) attribute should be written.

Refer to the documentation for individual input types for more details.