## Forum archive 2000-2006

### Michael Gage - num_cmp

by Arnold Pizer -
Number of replies: 0
 num_cmp topic started 1/4/2001; 11:02:06 PMlast post 9/7/2004; 11:10:59 AM
Michael Gage - num_cmp
1/4/2001; 11:02:06 PM (reads: 3529, responses: 1)

Description

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_ans-corr_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

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.

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.