Description
Creates an answer evaluator which checks numerical answers.
Syntax
num_cmp(number, options)
num_cmp([num1, num2], options)
Params
The first argument is the correct numerical answer, or one or more
correct answers placed in square brackets. The options are specified in
key => value (see Options)
Options
Option key  Option value  Default  mode  'std'  (default)  allows any expression evaluating to a number
'frac'  fractions are allowed
'arith'  arithmetic expressions allowed
'strict'  only numbers are allowed  'std'  tol  an absolute tolerance for checking answers  the default is to use relative tolerance   reltol   a relative tolerance given in percent. The submitted answer is judged correct if submit_anscorr_ans < .01 * reltol *corr_ans .  .01 per cent  format  defines formatting for printing the correct answer using the perl and C conventions.  '%0.5f'  units  specifies that the answer must include units and specifies the units used for the correct answer.   strings  specifies a list of words which are also
allowed. (e.g.  ['infinity','minus_infinity','undefined'] ). Note the
required square brackets.  
Returns
One (or more) answer evaluators
Examples
* num_cmp( 5, mode => 'strict' ) allows only 5 as an answer. No calculations are done.
* num_cmp( 5, mode => 'arith' ) allows (3+7)/2 as an answer but not (2 +6)/2 + cos(0)
* num_cmp( 5, mode => 'frac' )
allows 10/2 as an answer but not 3+5. This option is intended to allow
numbers containing fractions, but it general will not do arithmetic
operations.
* num_cmp( 5 ) or num_cmp(5, mode =>'std') allow cos(0) + e^0 +6/2 as an answer
* num_cmp(10, tol => 1) requires an answer between 9 and 11.(There is ambiguity at the endpoints.)
* num_cmp(10, reltol=>1) requires an answer between 9.9 and 10.1  i.e. within 1% of the correct answer. (reltol is defined in percent!)
* num_cmp( 3.1415926, format =>'%0.3f' ) prints as 3.141
* num_cmp( 3.14159, format => '%0.4e' ) prints as 3.1415
* num_cmp( 3.14159, format =>'%0.3g' )
gives 4 figures in either fixed point or exponential notation depending
on the size. In this case 3.14. For very small or large numbers the
answer would be printed using exponential notation.
* num_cmp(5, units => 'cm')
requires '5 cm' or '50 mm' or '.05 m' as an answer. The submitted
answer must have a space before the unit and no spaces within the units.
* num_cmp(5, strings =>['undefined']) requires either a 5 or 'undefined' as an answer.
Notes
The options can be used in any combination that makes sense, and probably some that don't. One exception: reltol and tol cannot be used together.
See Also
There are many aliases for the various forms of num_cmp. For example strict_num_cmp(\$ans) is roughly equivalent to num_cmp(\$num, mode => 'strict') . There is also std_num_cmp , frac_num_cmp , etc.
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