fix: implement unary NOT case for reduceExpr (#415)

Fixes #414
climateinteractive · Dec 5, 2023 · ce66990 · ce66990
1 parent 9269098
commit ce66990
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diff --git a/packages/parse/src/ast/reduce-expr.spec.ts b/packages/parse/src/ast/reduce-expr.spec.ts
@@ -18,6 +18,10 @@ describe('reduceExpr', () => {
     expect(reduceExpr(unaryOp('+', num(3)))).toEqual(num(3))
     expect(reduceExpr(unaryOp('-', num(3)))).toEqual(num(-3))
 
+    expect(reduceExpr(unaryOp(':NOT:', num(2)))).toEqual(num(0))
+    expect(reduceExpr(unaryOp(':NOT:', num(1)))).toEqual(num(0))
+    expect(reduceExpr(unaryOp(':NOT:', num(0)))).toEqual(num(1))
+
     expect(reduceExpr(binaryOp(num(3), '+', num(2)))).toEqual(num(5))
     expect(reduceExpr(binaryOp(num(3), '-', num(2)))).toEqual(num(1))
     expect(reduceExpr(binaryOp(num(3), '*', num(2)))).toEqual(num(6))

diff --git a/packages/parse/src/ast/reduce-expr.ts b/packages/parse/src/ast/reduce-expr.ts
@@ -50,7 +50,15 @@ export function reduceExpr(expr: Expr, opts?: ReduceExprOptions): Expr {
             return unaryOp('-', child)
           }
         case ':NOT:':
-          throw new Error('not yet implemented')
+          if (child.kind === 'number') {
+            // Use the same behavior as C and negate the numeric value.  ("The result of the
+            // logical negation operator ! is 0 if the value of its operand compares unequal
+            // to 0, 1 if the value of its operand compares equal to 0.")
+            return num(child.value === 0 ? 1 : 0)
+          } else {
+            // Cannot simplify further
+            return unaryOp(':NOT:', child)
+          }
         default:
           assertNever(expr)
       }