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Add ranged random generation

--- a/libstd/rand.myr

+++ b/libstd/rand.myr

@@ -48,9 +48,9 @@

 pkg std =

 	type rng

-	/* no mkrng() yet because we don't have anything to automatically

-	   seed it with yet */

 	const mksrng	: (seed : uint32 -> rng#)

+	generic rand	: (rng : rng#, lo : @a::(tcnum,tctest,tcint), hi : @a::(tcnum,tctest,tcint) -> @a::(tcnum,tctest,tcint))

+	generic randN	: (rng : rng# -> @a::(tcnum,tctest,tcint))

 	const rand32	: (rng : rng# -> uint32)

 ;;

@@ -59,6 +59,7 @@

 	i	: uint32

 ;;

+/* allocates and initializes a random number generator */

 const mksrng = {seed

 	var rng

@@ -67,6 +68,7 @@

 	-> rng

 }

+/* initializes a random number generator from the seed `seed`. */

 const init = {rng, seed

 	var i

@@ -77,7 +79,50 @@

 	rng.i = i

 }

+/*

+   Generates a random integer from `rng` in the range [lo, hi],

+   returning the value. The range [lo, hi) must be positive,

+   nonempty, and the difference between hi and lo must be

+   less then 2^(type_bits - 1)

+*/

+generic rand = {rng, lo, hi -> @a::(tcint,tcnum,tctest)

+	var span, div 

+	var maxrand

+	var val

+	span = hi - lo

+	maxrand = (1 << (8*sizeof(@a)-1)) - 1

+

+	assert(hi - lo > 0, "rand.myr: range for random values must be >= 1")

+	assert(span < maxrand, "rand.myr: span of ranges is too large")

+	div = maxrand/(span+1)

+	val = (randN(rng) & maxrand) / div

+

+	while val >= span

+		val = randN(rng) / div

+	;;

+	-> val + lo

+}

+

+/*

+   Generates a random integer of any size from the

+   random number generator `rng`.

+*/

+generic randN = {rng -> @a::(tcint,tcnum,tctest)

+	var i, val

+

+	val = 0

+	for i = 0; i < sizeof(@a)/4; i++

+		val <<= 8*sizeof(@a)

+		val |= rand32(rng) castto(@a::(tcint,tcnum,tctest))

+	;;

+	-> val

+}

+

+/*

+   generates a 32 bit unsigned random number

+   from the random number generator `rng`.

+*/

 const rand32 = {rng

 	var x

@@ -94,6 +139,7 @@

 }

+/* updates random number generator state when we tick over. */

 const next = {rng

 	var k

 	var y

--- a/libstd/test.myr

+++ b/libstd/test.myr

@@ -108,8 +108,8 @@

 	var i

 	r = std.mksrng(10)

-	for i = 0; i < 10; i++

-		std.put("r[%i] = %l\n", i, std.rand32(r) castto(int64))

+	for i = 0; i < 300; i++

+		std.put("r[%i] = %l\n", i, std.rand(r, 5, 10) castto(int64))

 	;;

 	std.put("\n");

 }

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -1567,7 +1567,7 @@

     } else if ((t->type >= Tybyte && t->type <= Tyulong) || t->type == Tychar) {

         uval = n->lit.intval;

         if (uval < uvranges[t->type][0] || uval > uvranges[t->type][1])

-            fatal(n->line, "Literal value %llu out of range for type \"%s\"", tystr(t));

+            fatal(n->line, "Literal value %llu out of range for type \"%s\"", uval, tystr(t));

     }

 }