added := for initialization/declaration

examples/custom_type.mers

@@ -4,7 +4,7 @@ type elem [int []/elem]
 fn print_linked_list(start elem) {
     loop {
         println(start.0.to_string())
-        elem = start.1
+        elem := start.1
         switch! elem {
             [] {
                 println("[END]")

examples/get_ref.mers

@@ -1,9 +1,9 @@
-list = [1 2 3 4 5 6 7 8 9 ...]
+list := [1 2 3 4 5 6 7 8 9 ...]
 
 // calling get on an &list will get a reference
 &list.get(2).assume1() = 24
 // calling get on a list will get a value
-should_not_be_changeable = list.get(3).assume1()
+should_not_be_changeable := list.get(3).assume1()
 &should_not_be_changeable = 24
 
 if list.get(2) != [24] println("[!!] list.get(2) != 24 (was {0})".format(list.get(2).to_string()))

examples/iterators.mers

@@ -4,7 +4,7 @@ fn map_string_to_int(list [string ...] func fn((string int))) {
         // this function will be called by the for loop
         // whenever it wants to retrieve the next item in the collection.
         // get the element
-        elem = &list.remove(0)
+        elem := &list.remove(0)
         switch! elem {
             // if the element was present, run the map function to convert it from a string to an int and return the result
             [string] {
@@ -24,8 +24,8 @@ for v ["1" "2" "5" "-10" ...].map_string_to_int((s string) s.parse_int().assume1
 // returns an iterator to iteratively compute square numbers
 // using the fact that (n+1)^2 = n^2 + 2n + 1
 fn square_numbers() {
-    i = 0
-    val = 0
+    i := 0
+    val := 0
     () {
         &val = val + { 2 * i } + 1
         &i = i + 1

examples/macro.mers

@@ -1,8 +1,8 @@
-val = "some string"
-val = !(mers {
+val := "some string"
+val := !(mers {
     println("macro is running now!")
     "macro returned value"
 })
 println(val)
-val = !(mers "my_macro.mers")
+val := !(mers "my_macro.mers")
 println(val)

examples/modify_variable.mers

@@ -1,9 +1,10 @@
 // NOTE: Might change, but this is the current state of things
-x = 10
-t = thread(() {
+x := 10
+t := thread(() {
     sleep(0.25)
     println(x.to_string())
 })
-// if this was x = 20 instead, the thread would still be using the old x = 10 value.
-&x = 20
+&x = 20 // -> 20 20 because it modifies the original variable x
+// x := 20 // -> 10 20 because it shadows the original variable x
 t.await()
+println(x.to_string())

examples/thread.mers

@@ -1,17 +1,17 @@
 // this is true by default so the example doesn't finish too quickly or too slowly depending on your hardware.
 // you can set it to false and tweak the max value for a more authentic cpu-heavy workload.
-fake_delay = true
+fake_delay := true
 
 // this will be shared between the two threads to report the progress in percent (0-100%).
-progress = 0
+progress := 0
 
 // an anonymous function that sums all numbers from 0 to max.
 // it captures the progress variable and uses it to report its status to the main thread, which will periodically print the current progress.
 // once done, it returns a string with the sum of all numbers.
-calculator = (max int) {
-    sum = 0
+calculator := (max int) {
+    sum := 0
     for i max {
-        i = i + 1
+        i := i + 1
         // println("i: {0} s: {1}".format(i.to_string() sum.to_string()))
         &sum = sum + i
         if fake_delay sleep(1)
@@ -21,7 +21,7 @@ calculator = (max int) {
 }
 
 // start the thread. if fake_delay is true, calculate 1+2+3+4+5+6+7+8+9+10. if fake_delay is false, count up to some ridiculously large number.
-slow_calculation_thread = calculator.thread(if fake_delay 10 else 20000000)
+slow_calculation_thread := calculator.thread(if fake_delay 10 else 20000000)
 
 // every second, print the progress. once it reaches 100%, stop
 loop {
@@ -31,6 +31,6 @@ loop {
 }
 
 // use await() to get the result from the thread. if the thread is still running, this will block until the thread finishes.
-result = slow_calculation_thread.await()
+result := slow_calculation_thread.await()
 
 println("Thread finished, result: {0}".format(result))

mers/src/lang/code_parsed.rs

@@ -40,8 +40,8 @@ impl SStatementEnum {
 pub struct SStatement {
     /// if the statement is a Variable that doesn't exist yet, it will be initialized.
     /// if it's a variable that exists, but is_ref is false, an error may show up: cannot dereference
-    /// NOTE: Maybe add a bool that indicates a variable should be newly declared, shadowing old ones with the same name.
-    pub output_to: Option<(Box<SStatement>, usize)>,
+    /// if the third value is true, the variable will always be initialized, shadowing previous mentions of the same name.
+    pub output_to: Option<(Box<SStatement>, usize, bool)>,
     pub statement: Box<SStatementEnum>,
     pub force_output_type: Option<VType>,
 }
@@ -55,7 +55,12 @@ impl SStatement {
         }
     }
     pub fn output_to(mut self, statement: SStatement, derefs: usize) -> Self {
-        self.output_to = Some((Box::new(statement), derefs));
+        self.output_to = Some((Box::new(statement), derefs, false));
+        self
+    }
+    /// like output_to, but always initializes the variable (shadows previous variables of the same name)
+    pub fn initialize_to(mut self, statement: SStatement, derefs: usize) -> Self {
+        self.output_to = Some((Box::new(statement), derefs, true));
         self
     }
     // forces the statement's output to fit in a certain type.
@@ -248,7 +253,7 @@ impl FormatGs for SStatement {
         form: &mut super::fmtgs::FormatInfo,
         file: Option<&crate::parsing::file::File>,
     ) -> std::fmt::Result {
-        if let Some((opt, derefs)) = &self.output_to {
+        if let Some((opt, derefs, is_init)) = &self.output_to {
             // TODO!
             match opt.statement.as_ref() {
                 // SStatementEnum::Variable(name, is_ref) => {
@@ -261,7 +266,13 @@ impl FormatGs for SStatement {
                 //     )?;
                 // }
                 _ => {
-                    write!(f, "{}{} = ", "*".repeat(*derefs), opt.with(info, file))?;
+                    write!(
+                        f,
+                        "{}{} {} ",
+                        "*".repeat(*derefs),
+                        opt.with(info, file),
+                        if *is_init { ":=" } else { "=" }
+                    )?;
                 }
             }
         }

mers/src/lang/global_info.rs

@@ -25,6 +25,11 @@ pub struct GlobalScriptInfo {
     pub custom_type_names: HashMap<String, usize>,
     pub custom_types: Vec<VType>,
 
+    /// if true, trying to assign to the reference of a variable that doesn't exist yet will create and initialize that variable.
+    /// if false, variables will only be initialized if this is explicitly stated.
+    /// settings this to true is useful for "x = 2; x = 5;" syntax in parser implementations that don't differenciate initialization and assignment syntactically.
+    pub to_runnable_automatic_initialization: bool,
+
     pub formatter: ColorFormatter,
 
     pub log: Logger,
@@ -94,6 +99,7 @@ impl Default for GlobalScriptInfo {
             enum_variants: Self::default_enum_variants(),
             custom_type_names: HashMap::new(),
             custom_types: vec![],
+            to_runnable_automatic_initialization: false,
             formatter: Default::default(),
             log: Logger::new(),
         }

mers/src/lang/to_runnable.rs

@@ -371,8 +371,9 @@ fn statement_adv(
             }
             SStatementEnum::Variable(v, is_ref) => {
                 let existing_var = linfo.vars.get(v);
+                let is_init_force = if let Some(v) = &to_be_assigned_to { *v.1 } else { false };
                 // we can't assign to a variable that doesn't exist yet -> create a new one
-                if existing_var.is_none() {
+                if is_init_force || (existing_var.is_none() && ginfo.to_runnable_automatic_initialization) {
                     // if to_be_assigned_to is some (-> this is on the left side of an assignment), create a new variable. else, return an error.
                     if let Some((t, is_init)) = to_be_assigned_to {
                         *is_init = true;
@@ -401,7 +402,7 @@ fn statement_adv(
                         *is_ref
                     )
                 } else {
-                    unreachable!()
+                    return Err(ToRunnableError::UseOfUndefinedVariable(v.clone()));
                 }
             }
             SStatementEnum::FunctionCall(v, args) => {
@@ -678,8 +679,9 @@ fn statement_adv(
             return Err(ToRunnableError::StatementRequiresOutputTypeToBeAButItActuallyOutputsBWhichDoesNotFitInA(force_opt.clone(), real_output_type, VType { types: problematic_types }));
         }
     }
-    if let Some((opt, derefs)) = &s.output_to {
-        let mut is_init = false;
+    if let Some((opt, derefs, is_init)) = &s.output_to {
+        // if false, may be changed to true by statement_adv
+        let mut is_init = *is_init;
         let optr = statement_adv(
             opt,
             ginfo,

mers/src/parsing/parse.rs

@@ -1005,23 +1005,21 @@ pub mod implementation {
                     )
                     .to()
                 }
-                // 000 =
+                // 000 = :=
                 (0..=0, Some('=')) => {
                     file.next();
-                    // NOTE: Old code to change `x = 10` to `&x = 10`
-                    // match out.statement.as_mut() {
-                    //     SStatementEnum::Variable(name, r) => {
-                    //         if name.starts_with("*") {
-                    //             *name = name[1..].to_owned();
-                    //         } else {
-                    //             *r = true
-                    //         }
-                    //     }
-                    //     _ => {}
-                    // }
-                    // NOTE: Set this 0 to 1 to prevent a = b = c from being valid
                     parse_statement(file)?.output_to(out, 0)
                 }
+                (0..=0, Some(':'))
+                    if matches!(
+                        file.get_char(file.get_pos().current_char_index + 1),
+                        Some('=')
+                    ) =>
+                {
+                    file.next();
+                    file.next();
+                    parse_statement(file)?.initialize_to(out, 0)
+                }
                 _ => break,
             };
         }