Fix `roll` and add its more general cousin `rotate`

4 files changed, 58 insertions, 6 deletions

diff --git a/bf.prn b/bf.prn
index 59e9727..c989655 100644
--- a/bf.prn
+++ b/bf.prn
@@ -75,7 +75,7 @@ dup 0 > while
 			else
 				ord 256 %
 			end
-			#{}"Input put on stack " print dup print lf
+			#"Input put on stack " print dup print lf
 		end
 		c ">" = if -1 roll end
 		c "<" = if 1 roll end
diff --git a/functions.cpp b/functions.cpp
index f4beeb9..4e67bfa 100644
--- a/functions.cpp
+++ b/functions.cpp
@@ -321,7 +321,7 @@ unordered_map<string,function<void(vector<Stackitem>&,unordered_map<string,Stack
 		}
 		scopestack.pop();
 	}},
-	//positive n: roll OFF top to bottom; negative n: roll off bottom ONTO top
+	//positive n: roll off bottom ONTO top (clockwise); negative n: roll OFF top to bottom (anti-clockwise)
 	{"roll",[](vector<Stackitem> &S,unordered_map<string,Stackitem> &variables){
 		BUILTIN_GUARD_STACKSIZE("roll",1)
 		Stackitem ns=move(S.back()); S.pop_back();
@@ -341,7 +341,6 @@ unordered_map<string,function<void(vector<Stackitem>&,unordered_map<string,Stack
 			S.insert(S.begin(),n,Stackitem());
 			for(int i=0;i<n;i++)S[i]=move(tempstore[i]);
 		} else {
-			//cerr<<"rolling back n="<<n<<endl;
 			vector<Stackitem> tempstore;
 			tempstore.reserve(n);
 			for(int i=0;i<n;i++)tempstore.push_back(move(S[i]));
@@ -349,6 +348,39 @@ unordered_map<string,function<void(vector<Stackitem>&,unordered_map<string,Stack
 			for(int i=0;i<n;i++)S.push_back(move(tempstore[i]));
 		}
 	}},
+	//positive n: rotate off bottom ONTO top (clockwise); negative n: rotate OFF top to bottom (anti-clockwise)
+	{"rotate",[](vector<Stackitem> &S,unordered_map<string,Stackitem> &variables){
+		BUILTIN_GUARD_STACKSIZE("rotate",2)
+		Stackitem timess=move(S.back()); S.pop_back();
+		Stackitem ns=move(S.back()); S.pop_back();
+		if(ns.type!=SIT_INT)throw string("First argument to 'rotate' not a number");
+		if(timess.type!=SIT_INT)throw string("Second argument to 'rotate' not a number");
+		int n=ns.intval,times=timess.intval;
+		bool negative=times<0;
+		if(negative)times=-times;
+		if(n>S.size()||n<0)throw string("Invalid number of items in builtin 'rotate'");
+		if(n==0)return;
+		if(S.size()<2)return;
+		times%=n;
+		if(times==0)return;
+
+		if(negative){
+			vector<Stackitem> tempstore;
+			tempstore.reserve(times);
+			const int ssz=S.size();
+			for(int i=ssz-times;i<ssz;i++)tempstore.push_back(move(S[i]));
+			S.erase(S.end()-times,S.end());
+			S.insert(S.end()-(n-times),times,Stackitem());
+			for(int i=0;i<times;i++)S[ssz-n+i]=move(tempstore[i]);
+		} else {
+			vector<Stackitem> tempstore;
+			tempstore.reserve(times);
+			const int ssz=S.size();
+			for(int i=0;i<times;i++)tempstore.push_back(move(S[ssz-n+i]));
+			S.erase(S.end()-n,S.end()-(n-times));
+			for(int i=0;i<times;i++)S.push_back(move(tempstore[i]));
+		}
+	}},
 	//leaves the string on the stack
 	{"stridx",[](vector<Stackitem> &S,unordered_map<string,Stackitem> &variables){
 		BUILTIN_GUARD_STACKSIZE("stridx",2)
@@ -473,15 +505,17 @@ unordered_map<string,function<void(vector<Stackitem>&,unordered_map<string,Stack
 	}},
 	{"rand",[](vector<Stackitem> &S,unordered_map<string,Stackitem> &variables){
 		BUILTIN_GUARD_STACKSIZE("rand",0)
-		assert(RAND_MAX==0x7fffffff);
+#if RAND_MAX != 0x7fffffff
+# error RAND_MAX should be 0x7fffffff for Postrun
+#endif
 		S.emplace_back(rand());
 	}},
 	//`to` exclusive
 	{"randr",[](vector<Stackitem> &S,unordered_map<string,Stackitem> &variables){
 		BUILTIN_GUARD_STACKSIZE("rand",2)
 		assert(RAND_MAX==0x7fffffff);
-		const Stackitem from=move(S.back()); S.pop_back();
 		const Stackitem to=move(S.back()); S.pop_back();
+		const Stackitem from=move(S.back()); S.pop_back();
 		if(from.type!=SIT_INT)throw string("First argument to 'randr' not a number");
 		if(to.type!=SIT_INT)throw string("Second argument to 'randr' not a number");
 		if(to.intval<=from.intval)throw string("Arguments to 'randr' form an empty range");
diff --git a/reference.md b/reference.md
index 13c7b2f..807664a 100644
--- a/reference.md
+++ b/reference.md
@@ -35,7 +35,8 @@ n `get` | Get value of variable with name `n`
 n `swapoutvar` | Get value of variable with name `n`, *moving* onto the stack instead of copying
 `enterscope` | Enter a function variable scope
 `leavescope` | Leave a function variable scope
-n `roll` | Roll the stack by `n`; positive n: roll OFF top to bottom; negative n: roll off bottom ONTO top
+t `roll` | Roll the stack `t` times; positive n: roll off bottom ONTO top (clockwise); negative n: roll OFF top to bottom (anti-clockwise)
+n t `rotate` | Rotate the top `n` items of the stack `t` times; positive n: rotate off bottom ONTO top (clockwise); negative n: rotate OFF top to bottom (anti-clockwise)
 s i `stridx` | Gets the character in string `s` index `i`, leaving `s` on the stack
 s `strlen` | Gets the length of string `s`, leaving `s` on the stack
 s a b `substr` | Gets the substring in `s` from index `a` to `b`, `b` exclusive; leaving `s` on the stack
diff --git a/test.prn b/test.prn
index 65549f9..ee29b6e 100644
--- a/test.prn
+++ b/test.prn
@@ -20,3 +20,20 @@ end
 
 42 "vv" store
 vv print lf
+
+pop
+
+1 2 3 4 5 6 stackdump
+4 1 rotate stackdump
+4 1 rotate stackdump
+4 1 rotate stackdump
+4 1 rotate stackdump
+5 2 rotate stackdump
+5 -2 rotate stackdump
+lf
+6 -1 rotate stackdump
+6 5 rotate stackdump
+-1 roll stackdump
+6 1 rotate stackdump
+6 7 rotate stackdump
+1 roll stackdump