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contextScientificNotation.pl - Allows entry of scientific notation.

This file implements a context in which students can enter answers in scientific notation. It tries hard to report useful error messages when the student's answer is not in the proper format, and it also allows you to control how many decimal digits they are allowed/required to enter, and how many the system will display.

This probably should be called LimitedScientificNotation since it does not allow any operations other than the ones needed in Scientific notation. In the future it may be renamed if we produce a computational scientific notation context.

To use this context, add

` loadMacros("contextScientificNotation.pl");`

to the top of your problem file, and then use

` Context("ScientificNotation");`

to select the context and make it active. You can create values in scientific notation in two ways:

` $n1 = Compute("1.23 x 10^3");`

or

` $n2 = ScientificNotation(1.23 * 10**3);`

(or even $n2 = ScientificNotation(1230), and it will be converted).

You can control how many digits are displayed by setting the snDigits flag in the context. For example,

` Context()->flags->set(snDigits=>2);`

sets the context to display at most 2 digits. The default is 6. By default, trailing zeros are removed, but you can ask that they be retained by issuing the command

` Context()->flags->set(snTrimZeros=>0);`

It is also possible to specify how many decimal digits the student must enter. For example,

` Context()->flags->set(snMinDigits=>3);`

would require the student to enter at least 3 digits past the decimal place (for a total of 4 significant digits, including the one to the left of the decimal). The default is 1 digit beyond the decimal. A value of 0 means that a decimal point and decimal values is optional.

Similarly,

` Context()->flags->set(snMaxDigits=>6);`

sets the maximum number to 6, so the student can't enter more than that. Setting this to 0 means no decimal places are allowed, effectively meaning students can only enter the numbers 0 through 9 (times a power of 10). Setting this to a negative number means that there is no upper limit on the number of digits the student may enter (this is the default).

As an example, in order to force a fixed precision of three digits of precision, use

```
Context()->flags->set(
snDigits => 3,
snTrimZeros => 0,
snMinDigits => 3,
snMaxDigits => 3,
);
```

Note that if you restrict the number of digits, you may need to adjust the tolerance values since the student may not be allowed to enter a more precise answer. In the example above, it would be appropriate to set the tolerance to .0001 and the tolType to "relative" in order to require the answers to be correct to the three digits that are shown.