Add Crystal port

...which is actually just a straight clone of the Ruby
version thanks to Crystal being heavily influenced by Ruby.

Signed-off-by: Eddie Ringle <eddie@ringle.io>

.gitignore

@@ -5,3 +5,4 @@
 genprime-*
 genprime.*.py
 *.rbc
+.crystal

Makefile

@@ -1,6 +1,6 @@
 ARGS=25000 100000
 
-all: genprime-java genprime-c genprime-f90 genprime-pyx genprime-py27 genprime-py30 genprime-objc genprime-cpp genprime-cs genprime-c-llvm genprime-c-icc genprime-c-clang genprime-swift
+all: genprime-java genprime-c genprime-f90 genprime-pyx genprime-py27 genprime-py30 genprime-objc genprime-cpp genprime-cs genprime-c-llvm genprime-c-icc genprime-c-clang genprime-swift genprime-crystal
 
 clean:
 	rm -f genprime.*.py *.pyc *.class genprime-* *.s *.bc *.ll *.rbc
@@ -47,6 +47,8 @@ version:
 	@echo
 	-swift -v
 	@echo
+	-crystal --version
+	@echo
 
 run: all
 	@echo "genprime (C GCC)"
@@ -114,6 +116,9 @@ run: all
 	@echo
 	@echo "genprime (Swift)"
 	@-./genprime-swift $(ARGS)
+	@echo
+	@echo "genprime (Crystal)"
+	@-./genprime-crystal $(ARGS)
 
 genprime-java: genprime.class
 
@@ -184,3 +189,7 @@ genprime.30.pyc: genprime.py
 genprime-swift: genprime.swift
 	-swift -O3 -sdk $(shell xcrun --show-sdk-path --sdk macosx) -o genprime-swift genprime.swift
 	@echo
+
+genprime-crystal: genprime.cr
+	-crystal build --release -o genprime-crystal genprime.cr
+	@echo

genprime.cr

@@ -0,0 +1,55 @@
+def isprime(x)
+    if x < 2
+        return 0
+    end
+    if x == 2
+        return 1
+    end
+    if x % 2 == 0
+        return 0
+    end
+    if x < 9
+        return 1
+    end
+    if (x + 1) % 6 != 0
+        if (x - 1) % 6 != 0
+            return 0
+        end
+    end
+    lim = Math.sqrt(x).to_i + 1
+    y = 3
+    while y <= lim
+        if x % y == 0
+            return 0
+        end
+        y += 2
+    end
+    return 1
+end
+
+def genprime(max)
+    count = 0
+    current = 1
+    while count < max
+        if isprime(current) != 0
+            count += 1
+        end
+        current += 1
+    end
+    return current - 1
+end
+
+start = ARGV[0].to_i
+stop = ARGV[1].to_i + 1
+i = start
+if start == 0
+    Process.exit
+end
+until i >= stop
+    starttime = Time.now
+    last = genprime(i)
+    endtime = Time.now
+    duration = endtime - starttime
+    printf "Found %8d primes in %10.5f seconds (last was %10d)\n", i, duration, last
+    i += start
+end