javascript - Polymer bind conditional attribute and evaluate attribute -

i wondering if possible using polymer expressions both bind attribute conditionally element while assigning value if bind true?

i know how both seperately:

pattern?="{{someboolean}}"  pattern="{{someboolean ? 'value if true' : 'value if false'}}"

but have been unsuccessful in accomplishing both without using javascript defined in element's prototype.

any assistance or advice appreciated!

edit:

in above example

if (someboolean) <input pattern="value if true"/> else if (!someboolean) //pattern attribute not bound , attribute assignment not occur <input/>

you can

<template if="{{ boolean }}">   {{ patterniftrue }} </template>

however think might changing in polymer 0.8.

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