Simplified expression evaluation

src/core/ExecuteToken.go

@@ -0,0 +1,46 @@
+package core
+
+import (
+	"git.urbach.dev/cli/q/src/cpu"
+	"git.urbach.dev/cli/q/src/errors"
+	"git.urbach.dev/cli/q/src/token"
+)
+
+// ExecuteToken performs an operation on a register with the given leaf operand.
+func (f *Function) ExecuteToken(operation token.Token, register cpu.Register, operand token.Token) error {
+	switch operand.Kind {
+	case token.Identifier:
+		name := operand.Text(f.File.Bytes)
+		variable := f.VariableByName(name)
+
+		if variable == nil {
+			return errors.New(&errors.UnknownIdentifier{Name: name}, f.File, operand.Position)
+		}
+
+		defer f.UseVariable(variable)
+		return f.ExecuteRegisterRegister(operation, register, variable.Value.Register)
+
+	case token.Number, token.Rune:
+		number, err := f.ToNumber(operand)
+
+		if err != nil {
+			return err
+		}
+
+		return f.ExecuteRegisterNumber(operation, register, number)
+
+	case token.String:
+		if operation.Kind == token.Assign {
+			value, err := f.EvaluateToken(operand)
+
+			if err != nil {
+				return err
+			}
+
+			f.ValueToRegister(value, register)
+			return err
+		}
+	}
+
+	return errors.New(errors.NotImplemented, f.File, operation.Position)
+}