Implemented expression parsing

src/build/Variable.go

@@ -1,10 +1,10 @@
 package build
 
-import "git.akyoto.dev/cli/q/src/build/token"
+import "git.akyoto.dev/cli/q/src/build/expression"
 
 // Variable represents a variable in a function.
 type Variable struct {
 	Name    string
-	Value   token.List
+	Value   *expression.Expression
 	IsConst bool
 }