Numerical question units and intervals

This is my proposal for how the numerical question function and interface should be improved.

[_]Allow evaluation of expressions

 Checking this would accept  5/2   0.5*5  5^2/2   5^(5-3)/2  25*10^-1  sqrt(25)/2

[_]Allow fraction type 2 1/2 as 2.5

[_] Translate "½" as "+.5" but give warning "Avoid ½ character in numerical expressions! We have translated ½ as +.5 to evaluate your answer."

 In the student question interface the answer box should:
 1) have a easy way to access with keyboard
    a) good "tab order": when opening a quiz question page the student will usually want to 
       answer the first question as his/her first option (tab order =10) 
           Assuming there are no other taborders set this would be first.
           "BASIC" numbering allows later refinements without renumbering. 
       if available "send in question" (tab order =15)
       answer next question (tab order= 20)
       if available "send in question" (tab order =25)
    b) Acesskeys (This is mined territory since there are no real standards (or
           rather several DIFFERENT standards) It would probably be best to let 
           people chose whether they want this activated)
  2) Have a (?) after the answer box linked to a popup explanation saying
      This is for a numerical answer

Answer 1:[ 2.5 ] Accepted error ± [0.5] Grade: [100%] Feedback:

Answer 2: [ 100.4..100.5) ] Accepted error ± Grade:

 Which would be interpreted  110.4 <= right < 100.5
  i.e. the round parentheses would mean that boundary not included in intervall
 or that one could enter evaluation strings like
 110.4<=ans<100.5||100.5<ans<=100.6
 (I know that this particular thing can be addressed by having
 100.5 +/-0  first than 100.5 +/-0.1)

Feedback:

.... Answer 10: Accepted error ± Grade: Feedback:

[_] differentiated unit feedback, which is all of:

         [_] tranlate dimensionless "units": % = *0.01; ppm=*1E-6 ppb. promille   
         [_] feedback for lacking unit [_]Feedback for accepted UNIT but wrong number 
         [_] feedback for "possibly right number" if unit is adjusted
         [_] feedback for "Unit not recognized, either misspelled, wrong type, or just not expected"
         (o) missed unit gives standard retry reduction of points (_)no reduction for missed unit (_)this reduction [___]  
 

Unit: [ ] (optional)

 Should accept arrays like kg, kilogram, kilograms , kilogramme, {"kilo gram", keelograhm} 
 where the ones enclosed in {} would be given feedback like
  We have interpretted keelograhm as a misspelling av kg Be aware that small spelling
   mistakes  like M in stead of m can lead to huge errors M=Mega=million
   m=milli= one thousandth" 

Alternative Units: Multiplier:[ ] Unit: [

Should possibly give feedback for misspelling including case errors  m milli  M Mega 

Multiplier: Unit: