This started as a comment, but it became too long, so I post it as an answer.

You say you don't want Python, but Python *would* be quick and complete, and to compare Python and MATLAB in "full-blown"-ity is quite harsh. I believe it would also fare well speed wise compared the the C# and Perl suggestions among the comments and answers.

I use the one-liner:

```
python -ic "from __future__ import division; from math import *;"
```

which I've bound to a keyboard shortcut which opens a terminal with this command, which gives me a lightning-fast competent calculator with `exp()`

, `sqrt()`

, `sin()`

, `log()`

, `pi`

, `e`

, etc.

If you just want a "`calc 5+7`

" variant, the *nix variete would be:

```
python -c "from __future__ import division; from math import *; print $*"
```

and on Windows you probably just need to replace `$*`

with `%*`

.

`from __future__ import division`

makes division use floating point instead of integer division as default, which is expected of a calculator. This is not needed if one uses Python 3 (which is what the `__future__`

part means).

`from math import *`

imports all math functions into the main namespace, so you can do `sin(2*pi)`

instead of `math.sin(2*pi)`

.

As an encore: to have a script that can be started in either interactive or direct mode:

```
#!/bin/sh
if [ ${#} = 0 ]; then
python -ic "from __future__ import division; from math import *;"
else
python -c "from __future__ import division; from math import *; print ${*};"
fi
```

(most probably trivially converted to Windows).