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Updated the answer checkers so that you can more easily specify how the correct answer shoudl be displayed. In the past, you could use something like Real(sqrt(2))->cmp(correct_ans=>"sqrt(2)") to do this, but that is awkward. Now the Compute() function (which parses and then evaluates a string) sets things up so that the original string will be what is used as the correct answer. That means Compute("sqrt(2)")->cmp will have the same result as the example above. You can also set the {correct_ans} properly of any Parser object to have that value used as the correct answer. For example $x = Real(sqrt(2)); $x->{correct_ans} = "sqrt(2)"; ANS($x->cmp) would also produce the same answer checker as the two previous examples. All three methods should work. Use the one that is most convenient for you.

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Clear error messages before doing the answer check (this clears old messages left over inclass this checker is called by another one, e.g. when using UNORDERD_ANS()).

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Don't give coordinate hints during parallel vector checks. Also fixed a typo.

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Added a new flag to the Formula()->cmp answer checker that allows a constant-valued formula to be evaluated and then use the checker for the resulting type. This is useful when you want the correct answer for a numeric check to be shown in a symbolic form (like "pi/4") rather than as a decimal number. To do this, use Formula("pi/4")->cmp(eval=>1); rather than Real(pi/4)->cmp, which would show the correct answer as 0.785398. Note that Formula("pi/4")->cmp would also match against pi/4, but it does it as a function rather than a number, so error messages might be issued indicating that the checker is expecting a formula that returns a number, rather than just a number; this might be confusing to a student. It would also accept answers like "pi/4-x+x" as correct, whereas with eval=>1 this would produce an error message saying that the answer was supposed to be a number not a formula returning a number. Similarly, if you want to show sqrt(2)/2 as the correct answer, use Context()->flags->set(reduceConstants=>0, reduceConstantFunctions=>0); Formula("sqrt(2)/2")->cmp(eval=>1); The first line tells the parser not to automatically reduce expressions that only involve constants, so that the value of the formula in the second line will not be reduced to a decimal before the cmp method is called.

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Don't reduce constants in the display of student answers (so they can tell how the parser interprets their answer). The drawback is that the final number is not displayed. (We may need to add more columns to the results display.)

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Use extra parens in the string version of the student's answer, but not in the professor's (unless the problem sets the showExtraParens flag).

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Make partial credit in list answer checkers be the default (now that WeBWorK can handle this).

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No longer produces the message that there are too many answers if hints are being shown about individual entries in a list. (This gave away the answer about which ones to remove.)

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Use the current context if the answer doesn't have one itself (like with Value objects).

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Added in functMaxConstantOfIntegration support in the adaptive parameter answer checking. Also added a flag to the formula answer checker that allows checking a formula up to a constant (for integration problems). This really just adds a new parameter to the context and adds that to the formula, so there is nothing deep about this. ANS(Formula("2x")->cmp(upToConstant=>1)); Finally, don't look for adaptive parameters if they aren't actually used in the professor's formula (even if they are defined).

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Added ability to have linear adaptive parameters in the function answer checker. It only works for real-valued functions, though. To use a parameter, use Context()->variables->add(a=>'Parameter'); and then use 'a' as a variable within your answer. The student will not be allowed to enter the parameter, but the professor will. Note that the correct answer will show the full professor's answer, including the parameters, even though the student can't type it. Is this the right behaviour?

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Fixed some inconsistencies between handing of matrices within the parser and Value packages. Added a predefined Matrix context.

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Added support for dimension warnings in the answer checker for formulas that return points, vectors or matrices.

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Diff to previous 2661

Added a file to perform WeBWorK-specific modifications to the Parser/Value packages. (I've tried to make these independent of WeBWorK, so you can use them in other perl code if you want to.) The parameters for fuzzy reals and some of the other parameters now are taken from the pg->{ansEvalDefaults} values (as defined in global.conf or course.conf). More still needs to be done with this, however.

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A number of fixes to make handing lists work better. In particular, you can now specify checks for whether the right kinds of parentheses (or none at all) are used on the student's answer. Some of the flags for the list checker have been changed to accommodate this.

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We need to protect the HTML in the professor's answer so that if it contains <, for example, it won't disappear.

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The answer checkers now work with subclasses of Formulas that are not part of the Value:: package tree itself (we call Value::isFormula() rather than checking the class directly). I also removed the various cmp_* flags that stored method names as they ended up not needing to be used (they were intended as a means of overriding the default method names, but subclassing turned out to be a better approach). I moved some initialization of the answer checker out of the anonymous subroutine that is installed in the checker and just have that subroutine call the correct answer's main checker (which I renamed). Finally, I changed the student_ans value to be an HTMLized version of the student answer, since the student could include things like < in his answer (e.g., for vectors), in which case his whole answer might disappear. I wonder if this couldn't be handled better at a higher level, as it seems wrong to make the student_ans be HTML rather than the parsed string. I originally thought Problem.pm could do the protecting of HTML special characters, but this won't work without additional changes, since some answer checkers put HTML into student_ans to mark sytanx errors in the student answer, and you DON'T want to protect those HTML characters. The student_ans field is probably being misused in this, and there might want to be another field that gets used by Problem.pm in place of student_ans (which can be HTML protected) when it is non-empty; say student_HTML or something like that. The answer checkers could use that field if it wants to add HTML to the student answer, and student_ans otherwise, with the assurance that it's HTML characters will be protected. That way, if a second answer checker calls the first (like some list checkers do), then the second checker doesn't have to worry about removing HTML from the student ans, and doesn't ahve to wonder whether the student_ans actually contains an error message or syntax markings rather than the actual student answer.

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Changed the string used for the student answer to be taken from the unevaluated formula rather than the fully-evaluated one. This leaves constants unreplaced, for one thing. Currently the parser combines constants automatically during the parse [which should be controllable by a flag], so student answers that produce numbers are fully evaluated at this point already, except for constant substitution. This could be changed so that even for numberic results, the student sees the parsed expression (rather than the numeric result), which might help them identify where they and the parser differ in their interpretation. It is still nice to see the final computed result, however, but there is no place to show the parsed input as well as the final result. One solution would be to add another column (wasting space). Another would be to make the value shown be "parsed-value = computed-value" when they are not the same thing. A bit ugly, but works within the current framework.

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Fixed typo in name of random generator.

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Fixed a number of minor problems with creating perl functions from formulas (this is done automatically as part of the function answer checker, so is showing up now that I have that checker in place). Also improved error messages in the function answer checker, and fixed a bug when students enter a constant list or union when the answer checker expects formulas.

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Removed unwanted side-effects of some type-match checks, and moved the ignoreStrings flag so that it is available for the checkers of ANY type.

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One more fix for handling intervals properly (I think it's really right this time). Also, named constants that end in numbers will produce TeX output with the number as a subscript (this was already true for variable names).

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Added support for unorderd list or formulas with partial credit. Fixed type mismatch reporting in formula answer checker. Fixed an error with Unions producing incorrect perl versions under some circumstances.

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Created the first draft of the Parser's function answer checker. Some work still needs to be done, in particular, type mismatches are not being reported, and lists are being processed only as ordered lists with no partial credit. This doesn't implement everything from fun_cmp. In particular, there is no support for parameter matching at the moment. This will have to be added, but I'm not quite sure how to do it when the function's return value is not a real number (e.g., an interval). On the other hand, this checker is more forgiving about domain errors: if tries a point where the professor's function is not defined, it ignores that one and looks for another (until it decides it can't find one). Once it has these points, it tries them on the student's answer, and if the student's function is undefined, then the student answer is wrong (since it is not defined somewhere that the professor's funciton is). This avoids the "Error evaluating student function at ..." messages, which just confused most students anyway.

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Improved error messages, particularly when the student enters a formula in an answer that should be constant, and also for incorrect answers in lists of answers. There are a few other miscellaneous output improvements as well.

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The Union answer checker now uses the generic List checker, so that it will be able to produce partial credit and hints about which Intervals are correct.

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Fixed some bugs in the handle of the context in ->string and ->TeX methods of Value objects.

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Fixed a typo in one of the parser answer checkers. Added a line that was incorrecctly removed in the parser.

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Added a String type to the Value package. Mostly this is to make it possible to generate an answer checker for it that uses the parser. It also makes it more consistent for handling things like stringify, especially when they are recursively called internally. Added new default strings "NONE" and "DNE", since these get used a lot. Modified how the default parameters are set up for the answer checkers, and how the answer checker reports the expected answer type in type mismatch error messages.

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Can now specify that the objects stringify themselfs in their TeX forms rather than their answer-string forms. This makes it easier to use the objects in the text of a problem (without having to call ->TeX explicitly each reference). Use Context()->texStrings to start outputting TeX strings, and Context()->normalStrings to switch back.

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Incorporated infinities into Parser package better. They have been stored as String objects (with extra data) in the parser, and I've left it that way, but now they convert to/from Vallue::Infinity objects correctly, and these are used for generating the output. Also added the Infinity answer checker, and adjusted the error messages produces by type mismatches in the answer checkers and elsewhere.

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Fixed some output issues with intervals and unions.

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Added ability to report incorrect coordinates in point and vector answers, and incorrect endpoints and endpoint types in intervals. Separated these kinds of checks from the typeMatch check, where they didn't really belong. Added ability to specify intervals and unions as strings in Interval() and Union(), which makes it easier to make constants of these types. There are still problems comparing intervals that contain infinities; I really need to make the infinity object to solve this, so have put off trying to fix that for now.

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Handle list entries that are not Value objects better.

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The List object's answer checker is now considerably improved. It will allow you to specify an unorderd or ordered check, and whether to print various kinds of hints for wrong answers. The checker can return partial credit, but WW doesn't deal well with this at the moment (some small changes to Problem.pm can take care of that). Partial credit should be based on $showPartialCorrectAnswers, but it is disabled for now. The list answer checker probably still needs some work, especially with non-numeric lists.

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Diff to previous 2596

Added answer checker for parallel vectors. Added option to number checker to have it not report type mismatches for the known strings (like 'infinity'). (Really need a class for infinities, and a Value.pm class for strings.)

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Diff to previous 2594

Have parser handle infinities better.

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Fixes for handling intervals better. In particular, deal better with ambiguous situations, like (1,2) that could be a point. You can use [a,a] to specify the single point a. I'd like to make {a} represent this (and maybe even {a,b,c} to form finite sets), but this would interfere with the use of { and } as alternative parentheses. (Does anyone really use these?) Do we need a cross product for intervals (and sets) as a means of representing regions in R^2 (or higher)?

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This is a preliminary attempt at adding answer checkers that use the parser. If you have a parser object (like a formula or a vector), you can use the ->cmp method to get an answer checker appropriate for the object. For example: Context('Vector'); $v = Vector(1,2,3); # print text of problem ANS($v->cmp); would produce an answer checker that matched against the vector <1,2,3>. Most of the parameters are set in the Context, but additional ones can be passed to the checker (this still needs work). See the sample problems for more examples. The checkers for Reals, Complexes, Points, Vectors, Matrices and Intervals work pretty well. The ones for List and Union objects need more work, as they only do an ORDERED check at the moment (the student answers must be in the same order). This needs to be fixed. The checker for Formula objects (which corresponds to fun_cmp) still needs to be written.

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