3.3 Sage Preparsing

The following files are relevant to preparsing in Sage:

SAGE_ROOT/local/bin/sage-sage,
SAGE_ROOT/local/bin/sage-preparse,
SAGE_ROOT/devel/sage/sage/misc/preparser.py

In particular, the file preparser.py contains the Sage preparser code. Here are some , and the following are some notes from it:

In Sage, methods can be called on integer and real literals - note that in pure Python this would be a syntax error. For example:
```
    sage: 16.sqrt()
    4
    sage: 87.factor()
    3 * 29
```
Raw literals are not preparsed, which can be useful from an efficiency point of view. Just like Python ints are denoted by an L, in Sage raw integer and floating literals are followed by an ``r'' (or ``R'') for raw, meaning not preparsed. Example:
```
    sage: a = 393939r
    sage: a
    393939
    sage: type(a)
    <type 'int'>
    sage: b = 393939
    sage: type(b)
    <type 'sage.rings.integer.Integer'>
    sage: a == b
    True
```
Raw literals can be very useful in certain cases. For instance, Python integers can be more efficient than Sage integers when they are very small; large Sage integers are much more efficient than Python integers, since they are implemented using the GMP C library.

Consult the file preparser.py for more details about Sage preparsing, more examples involving raw literals, etc.

When a file foo.sage is loaded in a Sage session, a preparsed version of foo.sage is created titled foo.py. The beginning of foo.py states: This file was *autogenerated* from the file foo.sage.

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