Parse branches

ldtext/Parser.fsy

@@ -18,16 +18,25 @@ open FSharp.Text.Lexing
 %start rung
 
 // return type of parser, marked by start token
-%type <Instr list> rung
+%type <Rung> rung
 
 %%
 
 rung:
-  | steps SEMICOLON EOF { $1 }
+  | steps SEMICOLON EOF { Rung $1 }
 
 steps:
   | { [] }
-  | instr steps { $1 :: $2 }
+  | instr steps { StepInstr $1 :: $2 }
+  | branch steps { StepBranch $1 :: $2 }
+
+branch:
+  | LEFT_BRACKET branch_arms RIGHT_BRACKET { Branch $2 }
+
+branch_arms:
+  | { [] }
+  | steps COMMA branch_arms { BranchArm $1 :: $3}
+  | steps { [ BranchArm $1 ] }
 
 instr:
   | IDENTIFIER LEFT_PAREN operands RIGHT_PAREN { { Op = $1; Args = $3 } }