FormattingDecimals
Formatting Decimals: PG Code Snippet
We show how to format decimals for display in PG problems.
PG problem file | Explanation |
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DOCUMENT(); loadMacros( "PGstandard.pl", "MathObjects.pl" ); TEXT(beginproblem()); |
Initialization: Standard. |
Context("Numeric"); Context()->variables->set(x=>{limits=>[2,4]}); # # both ln and log are natural log (base e) # $a = 6; # or $a = random(3,7,1); # # log base e # $b = sprintf("%0.3f", ln($a) ); # or log($a) $solution1 = Real("$b"); $f = Formula("ln(x)"); # or log(x) $solution2 = $f->eval(x=>$a); # # log base 10 is log10, logten, # ln(x)/ln(10), or log(x)/log(10) # $c = sprintf("%0.3f", ln($a)/ln(10) ); # or log($a)/log(10) $solution3 = Real("$c"); $g = Formula("ln(x)/ln(10)"); # or log(x)/log(10) $solution4 = $g->eval(x=>$a); |
Setup:
Since the domain of logarithmic functions are positive reals, we should set the domain of function evaluation to something like
Use perl's We used the logarithm change of base formula log_{10}(a) = log(a) / log(10) = ln(a) / ln(10) to get a logarithm base 10.
Note: If we load If you would like to define log base 2 (or another base) see AddingFunctions for how to define and add a new function to the context so that students can enter it in their answers. |
Context()->texStrings; BEGIN_TEXT Notice the formatting and rounding differences between \( $solution1 \) and \( $solution2 \). $BR $BR Try entering \( \ln($a), \log($a), \ln($a)/\ln(10), \log($a)/\log(10), \mathrm{logten}($a), \mathrm{log10}($a) \). $BR $BR \( \ln($a) = \) \{ ans_rule(20) \} $BR \( \ln($a) = \) \{ ans_rule(20) \} $BR \( \log_{10}($a) = \) \{ ans_rule(20) \} $BR \( \log_{10}($a) = \) \{ ans_rule(20) \} END_TEXT Context()->normalStrings; |
Main Text: Notice the difference in decimal formatting when "Show Correct Answers" is checked and you click "Submit Answers". |
ANS( $solution1->cmp() ); ANS( $solution2->cmp() ); ANS( $solution3->cmp() ); ANS( $solution4->cmp() ); ENDDOCUMENT(); |
Answer Evaluation: Standard. |