Data commit

Task/Additive-primes/Ksh/additive-primes.ksh

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+#!/bin/ksh
+
+# Prime numbers for which the sum of their decimal digits are also primes
+
+#	# Variables:
+#
+integer MAX_n=500
+
+#	# Functions:
+#
+#	# Function _isprime(n) return 1 for prime, 0 for not prime
+#
+function _isprime {
+	typeset _n ; integer _n=$1
+	typeset _i ; integer _i
+
+	(( _n < 2 )) && return 0
+	for (( _i=2 ; _i*_i<=_n ; _i++ )); do
+		(( ! ( _n % _i ) )) && return 0
+	done
+	return 1
+}
+
+#	# Function _sumdigits(n) return sum of n's digits
+#
+function _sumdigits {
+	typeset _n ; _n=$1
+	typeset _i _sum ; integer _i _sum=0
+
+	for ((_i=0; _i<${#_n}; _i++)); do
+		(( _sum+=${_n:${_i}:1} ))
+	done
+	echo ${_sum}
+}
+
+ ######
+# main #
+ ######
+
+integer i digsum
+for ((i=2; i<MAX_n; i++)); do
+	_isprime ${i} && (( ! $? )) && continue
+
+	digsum=$(_sumdigits ${i})
+	_isprime ${digsum} ; (( $? )) && printf "%4d " ${i}
+done
+print