Added simple variable lifetimes

src/build/VariableDefinition.go

@@ -2,6 +2,7 @@ package build
 
 import (
 	"git.akyoto.dev/cli/q/src/build/expression"
+	"git.akyoto.dev/cli/q/src/build/token"
 	"git.akyoto.dev/cli/q/src/errors"
 )
 
@@ -34,7 +35,37 @@ func (f *Function) CompileVariableDefinition(expr *expression.Expression) error
 		Register: reg,
 	}
 
-	f.Variables[name] = variable
-	f.CPU.Use(reg)
+	f.addVariable(variable)
+	f.useVariable(variable)
 	return nil
 }
+
+func (f *Function) addVariable(variable *Variable) {
+	variable.UsesRemaining = countIdentifier(f.Body, variable.Name)
+	f.Variables[variable.Name] = variable
+	f.CPU.Use(variable.Register)
+}
+
+func (f *Function) useVariable(variable *Variable) {
+	variable.UsesRemaining--
+
+	if variable.UsesRemaining < 0 {
+		panic("incorrect number of variable use calls")
+	}
+
+	if variable.UsesRemaining == 0 {
+		f.CPU.Free(variable.Register)
+	}
+}
+
+func countIdentifier(tokens token.List, name string) int {
+	count := 0
+
+	for _, t := range tokens {
+		if t.Kind == token.Identifier && t.Text() == name {
+			count++
+		}
+	}
+
+	return count
+}