fix: refactored grammar of prefix negation

Author: ascandone

Lexer.g4

@@ -38,7 +38,7 @@ PERCENTAGE_PORTION_LITERAL: [0-9]+ ('.' [0-9]+)? '%';
 STRING: '"' ('\\"' | ~[\r\n"])* '"';
 
 IDENTIFIER: [a-z]+ [a-z_]*;
-NUMBER: MINUS? [0-9]+ ('_' [0-9]+)*;
+NUMBER: [0-9]+ ('_' [0-9]+)*;
 ASSET: [A-Z][A-Z0-9]* ('/' [0-9]+)?;
 
 ACCOUNT_START: '@' -> pushMode(ACCOUNT_MODE);

Numscript.g4

@@ -19,6 +19,7 @@ valueExpr:
 	| NUMBER														# numberLiteral
 	| PERCENTAGE_PORTION_LITERAL									# percentagePortionLiteral
 	| monetaryLit													# monetaryLiteral
+	| op=MINUS valueExpr					# prefixExpr
 	| left = valueExpr op = DIV right = valueExpr					# infixExpr
 	| left = valueExpr op = (PLUS | MINUS) right = valueExpr		# infixExpr
 	| LPARENS valueExpr RPARENS										# parenthesizedExpr

internal/analysis/hover.go

@@ -183,6 +183,9 @@ func hoverOnExpression(lit parser.ValueExpr, position parser.Position) Hover {
 			return hover
 		}
 
+	case *parser.Prefix:
+		return hoverOnExpression(lit.Expr, position)
+
 	case *parser.FnCall:
 		return hoverOnFnCall(*lit, position)
 	}

internal/interpreter/evaluate_expr.go

@@ -69,7 +69,6 @@ func (st *programState) evaluateExpr(expr parser.ValueExpr) (Value, InterpreterE
 		return value, nil
 
 	case *parser.BinaryInfix:
-
 		switch expr.Operator {
 		case parser.InfixOperatorPlus:
 			return st.plusOp(expr.Left, expr.Right)
@@ -85,6 +84,16 @@ func (st *programState) evaluateExpr(expr parser.ValueExpr) (Value, InterpreterE
 			return nil, nil
 		}
 
+	case *parser.Prefix:
+		switch expr.Operator {
+		case parser.PrefixOperator(parser.PrefixOperatorMinus):
+			return st.unaryNegOp(expr.Expr)
+
+		default:
+			utils.NonExhaustiveMatchPanic[any](expr.Operator)
+			return nil, nil
+		}
+
 	case *parser.FnCall:
 		if !st.varOriginPosition {
 			err := st.checkFeatureFlag(flags.ExperimentalMidScriptFunctionCall)
@@ -214,6 +223,25 @@ func (st *programState) divOp(rng parser.Range, left parser.ValueExpr, right par
 	return Portion(*rat), nil
 }
 
+func (st *programState) unaryNegOp(expr parser.ValueExpr) (Value, InterpreterError) {
+	evExpr, err := evaluateExprAs(st, expr, expectOneOf(
+		expectMapped(expectMonetary, func(m Monetary) opNeg {
+			return m
+		}),
+
+		// while "x.map(identity)" is the same as "x", just writing "expectNumber" would't typecheck
+		expectMapped(expectNumber, func(bi big.Int) opNeg {
+			return MonetaryInt(bi)
+		}),
+	))
+
+	if err != nil {
+		return nil, err
+	}
+
+	return (*evExpr).evalNeg(st)
+}
+
 func castToString(v Value, rng parser.Range) (string, InterpreterError) {
 	switch v := v.(type) {
 	case AccountAddress:

internal/interpreter/infix_overloads.go

@@ -80,3 +80,26 @@ func (m Monetary) evalSub(st *programState, other parser.ValueExpr) (Value, Inte
 	}, nil
 
 }
+
+type opNeg interface {
+	evalNeg(st *programState) (Value, InterpreterError)
+}
+
+var _ opNeg = (*MonetaryInt)(nil)
+var _ opNeg = (*Monetary)(nil)
+
+func (m MonetaryInt) evalNeg(st *programState) (Value, InterpreterError) {
+	m1 := big.Int(m)
+	neg := new(big.Int).Neg(&m1)
+	return MonetaryInt(*neg), nil
+}
+
+func (m Monetary) evalNeg(st *programState) (Value, InterpreterError) {
+	m1 := big.Int(m.Amount)
+	neg := new(big.Int).Neg(&m1)
+	return Monetary{
+		Asset:  m.Asset,
+		Amount: MonetaryInt(*neg),
+	}, nil
+
+}

internal/interpreter/testdata/script-tests/minus-infix-monetary.num

@@ -0,0 +1,4 @@
+send [EUR/2 100] - [EUR/2 1] (
+  source = @world
+  destination = @dest
+)

internal/interpreter/testdata/script-tests/minus-infix-monetary.num.specs.json

@@ -0,0 +1,16 @@
+{
+  "$schema": "https://raw.githubusercontent.com/formancehq/numscript/main/specs.schema.json",
+  "testCases": [
+    {
+      "it": "should subtract the monetaries",
+      "expect.postings": [
+        {
+          "source": "world",
+          "destination": "dest",
+          "amount": 99,
+          "asset": "EUR/2"
+        }
+      ]
+    }
+  ]
+}

internal/interpreter/testdata/script-tests/minus-infix-number.num

@@ -0,0 +1,4 @@
+send [EUR/2 100-1] (
+  source = @world
+  destination = @dest
+)

internal/interpreter/testdata/script-tests/minus-infix-number.num.specs.json

@@ -0,0 +1,16 @@
+{
+  "$schema": "https://raw.githubusercontent.com/formancehq/numscript/main/specs.schema.json",
+  "testCases": [
+    {
+      "it": "should subtract the numbers",
+      "expect.postings": [
+        {
+          "source": "world",
+          "destination": "dest",
+          "amount": 99,
+          "asset": "EUR/2"
+        }
+      ]
+    }
+  ]
+}

internal/parser/__snapshots__/parser_test.snap

@@ -2173,12 +2173,19 @@ parser.Program{
                         },
                         Asset: "EUR/2",
                     },
-                    Amount: &parser.NumberLiteral{
+                    Amount: &parser.Prefix{
                         Range: parser.Range{
                             Start: parser.Position{Character:12, Line:0},
                             End:   parser.Position{Character:16, Line:0},
                         },
-                        Number: -100,
+                        Operator: "-",
+                        Expr:     &parser.NumberLiteral{
+                            Range: parser.Range{
+                                Start: parser.Position{Character:13, Line:0},
+                                End:   parser.Position{Character:16, Line:0},
+                            },
+                            Number: 100,
+                        },
                     },
                 },
             },