🐐 String interpolation

centvrion/ast_nodes.py

@@ -275,6 +275,7 @@ class DataRangeArray(Node):
 class String(Node):
   def __init__(self, value) -> None:
     self.value = value
+    self.quote = '"'
 
   def __eq__(self, other):
     return type(self) == type(other) and self.value == other.value
@@ -283,12 +284,60 @@ class String(Node):
     return f"String({self.value})"
 
   def print(self):
-    return f'"{self.value}"'
+    if self.quote == "'":
+      return f"'{self.value}'"
+    escaped = self.value.replace('{', '{{').replace('}', '}}')
+    return f'"{escaped}"'
 
   def _eval(self, vtable):
     return vtable, ValStr(self.value)
 
 
+def _flip_quotes(node, quote):
+  """Recursively set quote style on all String nodes in an expression tree."""
+  if isinstance(node, String):
+    node.quote = quote
+  for attr in vars(node).values():
+    if isinstance(attr, Node):
+      _flip_quotes(attr, quote)
+    elif isinstance(attr, list):
+      for item in attr:
+        if isinstance(item, Node):
+          _flip_quotes(item, quote)
+
+
+class InterpolatedString(Node):
+  def __init__(self, parts) -> None:
+    self.parts = parts
+
+  def __eq__(self, other):
+    return type(self) == type(other) and self.parts == other.parts
+
+  def __repr__(self):
+    return f"InterpolatedString([{rep_join(self.parts)}])"
+
+  def print(self):
+    result = '"'
+    for part in self.parts:
+      if isinstance(part, String):
+        result += part.value.replace('{', '{{').replace('}', '}}')
+      else:
+        _flip_quotes(part, "'")
+        result += '{' + part.print() + '}'
+        _flip_quotes(part, '"')
+    result += '"'
+    return result
+
+  def _eval(self, vtable):
+    magnvm = "MAGNVM" in vtable["#modules"]
+    svbnvlla = "SVBNVLLA" in vtable["#modules"]
+    pieces = []
+    for part in self.parts:
+      vtable, val = part.eval(vtable)
+      pieces.append(make_string(val, magnvm, svbnvlla))
+    return vtable, ValStr(''.join(pieces))
+
+
 class Numeral(Node):
   def __init__(self, value: str) -> None:
     self.value = value

centvrion/compiler/emit_expr.py

@@ -1,6 +1,6 @@
 from centvrion.errors import CentvrionError
 from centvrion.ast_nodes import (
-  String, Numeral, Fractio, Bool, Nullus, ID,
+  String, InterpolatedString, Numeral, Fractio, Bool, Nullus, ID,
   BinOp, UnaryMinus, UnaryNot,
   ArrayIndex, DataArray, DataRangeArray,
   BuiltIn, Invoca,
@@ -51,6 +51,25 @@ def emit_expr(node, ctx):
     tmp = ctx.fresh_tmp()
     return [f'CentValue {tmp} = cent_str("{_escape(node.value)}");'], tmp
 
+  if isinstance(node, InterpolatedString):
+    if len(node.parts) == 0:
+      tmp = ctx.fresh_tmp()
+      return [f'CentValue {tmp} = cent_str("");'], tmp
+    if len(node.parts) == 1:
+      return emit_expr(node.parts[0], ctx)
+    l_lines, l_var = emit_expr(node.parts[0], ctx)
+    r_lines, r_var = emit_expr(node.parts[1], ctx)
+    lines = l_lines + r_lines
+    acc = ctx.fresh_tmp()
+    lines.append(f"CentValue {acc} = cent_concat({l_var}, {r_var});")
+    for part in node.parts[2:]:
+      p_lines, p_var = emit_expr(part, ctx)
+      lines.extend(p_lines)
+      new_acc = ctx.fresh_tmp()
+      lines.append(f"CentValue {new_acc} = cent_concat({acc}, {p_var});")
+      acc = new_acc
+    return lines, acc
+
   if isinstance(node, Bool):
     tmp = ctx.fresh_tmp()
     v = "1" if node.value else "0"

centvrion/parser.py

@@ -1,10 +1,71 @@
 from rply import ParserGenerator
 
-from centvrion.lexer import all_tokens
+from centvrion.errors import CentvrionError
+from centvrion.lexer import Lexer, all_tokens
 from . import ast_nodes
 
 ALL_TOKENS = list(set([i[0] for i in all_tokens]))
 
+
+def _parse_interpolated(raw_value):
+  quote_char = raw_value[0]
+  inner = raw_value[1:-1]
+
+  if quote_char == "'" or len(inner) == 0:
+    return ast_nodes.String(inner)
+
+  parts = []
+  i = 0
+  current = []
+
+  while i < len(inner):
+    ch = inner[i]
+    if ch == '{':
+      if i + 1 < len(inner) and inner[i + 1] == '{':
+        current.append('{')
+        i += 2
+        continue
+      if current:
+        parts.append(ast_nodes.String(''.join(current)))
+        current = []
+      j = i + 1
+      depth = 1
+      while j < len(inner) and depth > 0:
+        if inner[j] == '{':
+          depth += 1
+        elif inner[j] == '}':
+          depth -= 1
+        j += 1
+      if depth != 0:
+        raise CentvrionError("Unclosed '{' in interpolated string")
+      expr_src = inner[i + 1:j - 1]
+      tokens = Lexer().get_lexer().lex(expr_src + "\n")
+      program = Parser().parse(tokens)
+      if len(program.statements) != 1:
+        raise CentvrionError("Interpolation must contain exactly one expression")
+      stmt = program.statements[0]
+      if not isinstance(stmt, ast_nodes.ExpressionStatement):
+        raise CentvrionError("Interpolation must contain an expression, not a statement")
+      parts.append(stmt.expression)
+      i = j
+    elif ch == '}':
+      if i + 1 < len(inner) and inner[i + 1] == '}':
+        current.append('}')
+        i += 2
+        continue
+      raise CentvrionError("Unmatched '}' in string (use '}}' for literal '}')")
+    else:
+      current.append(ch)
+      i += 1
+
+  if current:
+    parts.append(ast_nodes.String(''.join(current)))
+
+  if len(parts) == 1 and isinstance(parts[0], ast_nodes.String):
+    return parts[0]
+
+  return ast_nodes.InterpolatedString(parts)
+
 class Parser():
   def __init__(self):
     self.pg = ParserGenerator(
@@ -184,7 +245,7 @@ class Parser():
 
     @self.pg.production('expression : DATA_STRING')
     def expression_string(tokens):
-      return ast_nodes.String(tokens[0].value[1:-1])
+      return _parse_interpolated(tokens[0].value)
 
     @self.pg.production('expression : DATA_NUMERAL')
     def expression_numeral(tokens):