1 | initial version |

You can do

```
sage slopes.sage
```

to run the file from the command line. The bad interaction is probably between the ipython readline interface and a non-tty stdin, not with the preparser. Note that IPython does some undesirable things for file input. For one thing, it uses auto-indent, which makes it hard or impossible to input some more complicated loops (unless you use %cpaste).

Sage or Ipython could check if stdin is a tty and revert to "file processing" (i.e., not use readline etc.) if it's not, but apparently (judging from your example) it doesn't.

In any case, the preparser does apply a few more efficient tricks (such as factoring out constants) when you use `sage <file>`

, so it's better to use that if you can, rather than redirect the input. It has the side-effect of writing `slopes.sage.py`

into the current directory, though.

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