From 3fc6d221471a7a008fc0398da5be2861e9613fd7 Mon Sep 17 00:00:00 2001
From: Jegor Popow <juicedogegor@gmail.com>
Date: Sat, 7 Oct 2023 22:07:53 +0300
Subject: [PATCH] first iteration

---
 src/Expr.lama | 27 +++++++++++++++++--
 src/SM.lama   | 75 ++++++++++++++++++++++++++++++++++++++++++++++++---
 src/Stmt.lama | 29 +++++++++++++++++++-
 3 files changed, 125 insertions(+), 6 deletions(-)

diff --git a/src/Expr.lama b/src/Expr.lama
index b75803563..79e4ea1cb 100644
--- a/src/Expr.lama
+++ b/src/Expr.lama
@@ -3,7 +3,6 @@
 import List;
 import State;
 
-
 -- The evaluator itself: takes a state and an expression,
 -- returns integer value
 --
@@ -14,5 +13,29 @@ import State;
 --        Binop (string, expr, expr)
 
 public fun evalExpr (st, expr) {
-  failure ("evalExpr not implemented\n")
+  
+  fun applyOperator(op, lhs, rhs) {
+    -- printf("Opearator `%s` called on operands %d, %d\n", op, lhs, rhs);
+    case op of 
+        "+" -> lhs + rhs
+      | "-" -> lhs - rhs
+      | "*" -> lhs * rhs
+      | "/" -> lhs / rhs
+      | "%" -> lhs % rhs
+      | "==" -> lhs == rhs
+      | "!=" -> lhs != rhs
+      | "<" -> lhs < rhs
+      | "<=" -> lhs <= rhs
+      | ">" -> lhs > rhs
+      | ">=" -> lhs >= rhs
+      | "&&" -> lhs && rhs
+      | "!!" -> lhs !! rhs
+    esac    
+  }
+
+  case expr of 
+      Var (name) -> st(name)
+    | Const (value) -> value 
+    | Binop (op, lhs, rhs) -> applyOperator(op, evalExpr(st, lhs), evalExpr(st, rhs))
+  esac
 }
diff --git a/src/SM.lama b/src/SM.lama
index 5e9e82bd9..5ee96d122 100644
--- a/src/SM.lama
+++ b/src/SM.lama
@@ -27,7 +27,66 @@ public fun showSM (prg) {
 -- Stack machine interpreter. Takes an SM-configuration and a program,
 -- returns a final configuration
 fun eval (c, insns) {
-  failure ("SM eval not implemented\n")
+
+
+  fun applyOperator(op, lhs, rhs) {
+    -- printf("Opearator `%s` called on operands %d, %d\n", op, lhs, rhs);
+    case op of 
+        "+"  -> lhs + rhs
+      | "-"  -> lhs - rhs
+      | "*"  -> lhs * rhs
+      | "/"  -> lhs / rhs
+      | "%"  -> lhs % rhs
+      | "==" -> lhs == rhs
+      | "!=" -> lhs != rhs
+      | "<"  -> lhs < rhs
+      | "<=" -> lhs <= rhs
+      | ">"  -> lhs > rhs
+      | ">=" -> lhs >= rhs
+      | "&&" -> lhs && rhs
+      | "!!" -> lhs !! rhs
+    esac    
+  }
+
+
+  fun store([value:tail, state, world], name) {
+    [tail, state <- [name, value], world]
+  }
+
+  fun load([stack, state, world], name) {
+    [state(name):stack, state, world]
+  }
+
+  fun read([stack, state, world]) {
+    case readWorld(world) of 
+      [value, newWorld] ->  [value : stack, state, newWorld]
+    esac 
+  }
+
+  fun write([value:tail, state, world]) {
+    [tail, state, writeWorld(value, world)]
+  }
+
+  fun binop([rhs:lhs:tail, state, world], op) {
+    [applyOperator(op, lhs, rhs):tail, state, world]
+  } 
+
+  fun push([stack, state, world], value) {
+    [value : stack, state, world]
+  }
+
+  fun step(c@[stack, state, world], insn) {
+    case insn of
+        READ          -> read(c)
+      | WRITE         -> write(c)
+      | BINOP (op)    -> binop(c, op)
+      | LD    (name)  -> load(c, name)
+      | ST    (name)  -> store(c, name)
+      | CONST (value) -> push(c, value)
+    esac
+  } 
+
+  foldl (step, c, insns)
 }
 
 -- Runs a stack machine for a given input and a given program, returns an output
@@ -38,12 +97,22 @@ public fun evalSM (input, insns) {
 -- Compiles an expression into a stack machine code.
 -- Takes an expression, returns a list of stack machine instructions
 fun compileExpr (expr) {
-  failure ("compileExpr not implemented\n")
+  case expr of 
+      Var (name) -> {LD(name)}
+    | Const (value) -> {CONST(value)} 
+    | Binop (op, lhs, rhs) -> compileExpr(lhs) +++ compileExpr(rhs) +++ {BINOP(op)}
+  esac
 }
 
 -- Compiles a statement into a stack machine code.
 -- Takes a statement, returns a list of stack machine
 -- instructions.
 public fun compileSM (stmt) {
-  failure ("compileSM not implemented\n")
+  case stmt of 
+      Assn (name, expr) -> compileExpr(expr) +++ {ST(name)}
+    | Seq (first, second) -> compileSM(first) +++  compileSM(second)
+    | Skip -> {}
+    | Read (name) -> {READ, ST(name)} 
+    | Write (expr) -> compileExpr(expr) +++ {WRITE}
+  esac
 }
diff --git a/src/Stmt.lama b/src/Stmt.lama
index 67ec6db9e..34047d0c7 100644
--- a/src/Stmt.lama
+++ b/src/Stmt.lama
@@ -17,9 +17,36 @@ import World;
 --        Write  (expr)             |
 
 fun eval (c, stmt) {
-  failure ("Stmt eval not implemented\n")
+
+  fun applyAssn([st, world], name, expr) {
+    [st <- [name, evalExpr(st, expr)], world]
+  }
+
+  fun applySeq(c, first, second) {
+    var intermediate = eval(c, first);
+    eval (intermediate, second)
+  }
+
+  fun applyRead([st, world], name) {
+    case readWorld(world) of 
+      [value, newWorld] ->  [st <- [name, value], newWorld]
+    esac 
+  }
+
+  fun applyWrite([st, world], expr) {
+    [st, writeWorld(evalExpr(st, expr), world)]
+  }
+
+  case stmt of 
+      Assn (name, expr) -> applyAssn(c, name, expr)
+    | Seq (first, second) -> applySeq(c, first, second)
+    | Skip -> c 
+    | Read (name) -> applyRead(c, name) 
+    | Write (expr) -> applyWrite(c, expr)
+  esac
 }
 
+
 -- Evaluates a program with a given input and returns an output
 public fun evalStmt (input, stmt) {
   eval ([emptyState, createWorld (input)], stmt).snd.getOutput