#!/bin/rc
# math - basic arithmetic quiz
# usage: math [-q n] [-r n] [-o '+-*/%^']

# set some default values
rfork e
right=0
wrong=0
questions=20
range=1	# in digits
operands='+-'
start=`{date -n}

# parse optional flags
for(i in $*){
	switch($i){
	case -q
		questions=$2
		shift 2
	case -r
		range=$2
		shift 2
	case -o
		operands=''$2''
		shift 2
    }
}

# rnum: generate a random digit based on cpu clock
fn rnum{
	awk '{ print $2 }' /dev/time | sed 's/.*(.)$/\1/'
}

# ask math questions
opleft=$operands
for(i in `{seq $questions}){
	# generate random math puzzle
	a=`{rnum}
	b=`{rnum}
	if(test $range -gt 1){
		for(i in `{seq `{echo $range - 1 | bc}}){
			a=`{echo $a^`{rnum}}
			b=`{echo $b^`{rnum}}
		}
	}
	if(~ $#opleft 0)
		opleft=$operands
	if not{
		opused=`{echo $opleft | sed 's/^(.).*/\1/'}
		opleft=`{echo $opleft | sed 's/^.(.*)/\1/'}
	}
	echo $a $"opused $b
	correct=`{echo $a $"opused $b | bc}
	answer=`{read}
	# evaluate given answer
	while(! ~ $answer $correct){
		if(echo $answer | grep -s '^[-+]?[0-9]+$'){
			echo What?
			wrong=`{echo $wrong + 1 | bc}
		}
		if not
			echo Please type a number '(no decimals!)'
		answer=`{read}
	}
	echo Right!
	right=`{echo $right + 1 | bc}
}

# print result of math quiz
finish=`{date -n}
time=`{echo $finish - $start | bc}
total=`{echo $right + $wrong | bc}
timepq=`{echo $time / $total | bc}
if(~ $right 0)
	prct=0%
if not
	prct=`{echo 'scale=2 ; '$right' / '$total'' | bc | sed 's/\.//' | sed 's/$/%/'}
echo -n $right right, $wrong wrong '('$prct' correct)' in $time seconds '('$timepq's per answer)'
echo