VM Bytecode char to string instructions

New instrucions: CTOS and MKSTR. CTOS creates a string containing
a single (input) character. MKSTR creates a new blank string. Unit
tests included.

fixes: #42

Signed-off-by: Ava Affine <ava@sunnypup.io>

hyphae/instructions.toml

@@ -1,3 +1,13 @@
+# TODO: add the following info
+#   - introductory VM info (description, list of components)
+#   - info on the different data types
+#   - info on garbage collection
+#   - info on program execution
+#   - info on error handling
+#   - info on traps
+#   - info on numbers
+#   - info on symtable (and its uses)
+
 [[addressing_modes]]
 name = "expr"
 mutable = true
@@ -275,6 +285,12 @@ args = ["src"]
 output = ""
 description = "decrements number at source"
 
+[[instructions]]
+name = "ctos"
+args = ["src"]
+output = ""
+description = "mutates a char datum into a string datum"
+
 [[instructions]]
 name = "cton"
 args = ["src"]
@@ -317,6 +333,12 @@ args = []
 output = "a blank bytevector"
 description = "creates a blank bytevector"
 
+[[instructions]]
+name = "mkstr"
+args = []
+output = "an empty string"
+description = "creates a new empty string"
+
 [[instructions]]
 name = "index"
 args = ["collection", "index"]

hyphae/src/vm.rs

@@ -369,6 +369,16 @@ impl VM {
             }),
 
             // byte/char to and from number conversions
+            i::CTOS => access!(&instr.1[0], {
+                if let Datum::Char(schr) = **access!(&instr.1[0]) {
+                    let mut v = vec![];
+                    v.push(schr);
+                    Datum::String(v).into()
+                } else {
+                    e!("illegal argument to CTOS instruction");
+                }
+            }),
+
             i::CTON => access!(&instr.1[0], {
                 if let Datum::Char(schr) = **access!(&instr.1[0]) {
                     Datum::Number(Number::Fra(Fraction(schr as isize, 1))).into()
@@ -421,6 +431,8 @@ impl VM {
 
             i::MKBVEC => self.expr = Datum::ByteVector(vec![]).into(),
 
+            i::MKSTR  => self.expr = Datum::String(vec![]).into(),
+
             i::INDEX  => {
                 let Datum::Number(ref idx) = **access!(&instr.1[1]) else {
                     e!("illegal argument to INDEX instruction");
@@ -1067,23 +1079,20 @@ mod tests {
 
     #[test]
     fn isa_conversions() {
-        /* program:
-         * dupl %0, $ex
-         * cton $ex
-         * push $ex
-         * ntoc $ex
-         * push $ex
-         * ntoi $ex
-         * push $ex
-         * ntoe $ex
-         * push $ex
-         */
-
         let mut vm = VM::from(Program(vec![
             // load from stack into expr
             Instruction(i::DUPL,  vec![Operand(Address::Stack, 0),
                                        Operand(Address::Expr,  0)]),
 
+            // create a strunct and push to stack
+            Instruction(i::CTOS,  vec![Operand(Address::Expr, 0)]),
+            Instruction(i::PUSH,  vec![Operand(Address::Expr, 0)]),
+
+            // reset expr to original char
+
+            Instruction(i::DUPL,  vec![Operand(Address::Stack, 1),
+                                       Operand(Address::Expr,  0)]),
+
             // create a number and push to stack
             Instruction(i::CTON,  vec![Operand(Address::Expr, 0)]),
             Instruction(i::PUSH,  vec![Operand(Address::Expr, 0)]),
@@ -1112,7 +1121,8 @@ mod tests {
                 (1, Datum::Number(Number::Fra(Fraction(97, 1))).into()),
                 (2, Datum::Number(Number::Flt(Float(97.0))).into()),
                 (3, Datum::Number(Number::Fra(Fraction(97, 1))).into()),
-                (4, Datum::Char(b'a').into()),
+                (4, Datum::String(vec![b'a']).into()),
+                (5, Datum::Char(b'a').into()),
             ],
             syms: vec![],
             errr: None,