45, 46, 92

3 files changed, 93 insertions, 0 deletions

diff --git a/euler45.myr b/euler45.myr
new file mode 100644
index 0000000..3bf53fc
--- /dev/null
+++ b/euler45.myr
@@ -0,0 +1,30 @@
+use std
+
+const main = {
+	for var n: uint64 = 144; true; n++
+		var hn = n * (n * 2 - 1)
+		/* find pentagonal pn = n(3n-1)/2 */
+		/* n' < 2/sqrt(3)*n */
+		var i: uint64 = n * 148 / 128
+		var pn = i * (i * 3 - 1) / 2
+		while pn > hn
+			i--
+			pn = i * (i * 3 - 1) / 2
+		;;
+		if (pn != hn)
+			continue
+		;;
+		/* find triangle tn = n(n+1)/2, n'<2n */
+		i = n*2
+		var tn = i * (i + 1) / 2
+		while tn > hn
+			i--
+			tn = i * (i + 1) / 2
+		;;
+		if (tn != hn)
+			continue
+		;;
+		std.put("n = {}, h[n] = {}\n", n, hn)
+		break
+	;;
+}
diff --git a/euler46.myr b/euler46.myr
new file mode 100644
index 0000000..0aa1180
--- /dev/null
+++ b/euler46.myr
@@ -0,0 +1,36 @@
+use std
+
+const isprime = {x
+	if (x < 1)
+		-> false
+	;;
+	for var i = 2; i * i <= x; i++
+		if (x % i ==0)
+			-> false
+		;;
+	;;
+	-> true
+}
+
+const main = {
+	for var i = 9; true; i+=2
+		if (isprime(i))
+			continue
+		;;
+		var found = true
+		for var j = 1; true; j++
+			var t = i - j * j * 2
+			if t <= 0
+				break
+			;;
+			if (isprime(t))
+				found = false
+				break
+			;;
+		;;
+		if found
+			std.put("{}\n", i)
+			break
+		;;
+	;;
+}
diff --git a/euler92.myr b/euler92.myr
new file mode 100644
index 0000000..3092405
--- /dev/null
+++ b/euler92.myr
@@ -0,0 +1,27 @@
+use std
+
+const goto89 = {x
+	const sqrsum = {y
+		var sum = 0
+		while y > 0
+			var b = y % 10
+			y = y / 10
+			sum += b * b
+		;;
+		-> sum
+	}
+	while x != 1 && x != 89
+		x = sqrsum(x)
+	;;
+	-> x == 89
+}
+
+const main = {
+	var n = 0
+	for var i = 1; i < 10_000_000; i++
+		if goto89(i)
+			n++
+		;;
+	;;
+	std.put("{}\n", n)
+}