I've just been shown a brilliant calculator app called Soulver which is only available on Mac OS X

Maths on a Mac as it should be

Soulver is a new kind of calculator application which uses a simple yet powerful word-processor style interface instead of the traditional "button" approach to doing math.

Main Features

• No equals button - Soulver instantly calculates as you type.
• Multiple lines - Soulver lets you do math over multiple lines and edit previous expressions.
• Flexible to words - Soulver doesn't mind if you include words or labels between numbers.
• Basic functions - Soulver includes every standard calculator function, like sin(), cos() & tan()
• Clever English functions - Soulver includes some "English" math functions. For instance you can type "10% off $200" and get $180
• Floating palettes - Soulver's answer & stats palettes will give you conversions and statistics on your work as your type
• Save your work - like a word processor, Soulver allows you to save and reopen your work

This is a fantastic concept and I would really like to find it's equivalent for Windows and/or Linux.

Any suggestions?