add rounding

src/factorial.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"strings"
+)
+
+var factorialCompiled = makeRegex(`( *)(.|\n)+\!( *)`)
+
+type factorial struct {
+	value any
+	code  string
+	line  int
+	path  string
+}
+
+func parseFactorial(code UNPARSEcode, index int, codeline []UNPARSEcode) (factorial, bool, ArErr, int) {
+	trim := strings.TrimSpace(code.code)
+	trim = trim[:len(trim)-1]
+	val, success, err, i := translateVal(UNPARSEcode{code: trim, realcode: code.realcode, line: 1, path: ""}, 0, []UNPARSEcode{}, false)
+	if !success {
+		return factorial{}, false, err, i
+	}
+
+	return factorial{val, code.code, code.line, code.path}, success, ArErr{}, i
+}
+
+func isFactorial(code UNPARSEcode) bool {
+	return factorialCompiled.MatchString(code.code)
+}
+
+func fact(n number) number {
+	if n.Cmp(newNumber().SetInt64(0)) == 0 {
+		return newNumber().SetInt64(1)
+	}
+	result := newNumber().SetInt64(1)
+	for i := newNumber().SetInt64(2); i.Cmp(n) <= 0; i.Add(i, newNumber().SetInt64(1)) {
+		result.Mul(result, i)
+	}
+	return result
+}
+
+func runFactorial(f factorial, stack stack) (any, ArErr) {
+	val, err := runVal(f.value, stack)
+	if err.EXISTS {
+		return nil, err
+	}
+	switch x := val.(type) {
+	case number:
+		if !x.IsInt() {
+			return nil, ArErr{"Runtime Error", "cannot use factorial on non-integer", f.line, f.path, f.code, true}
+		}
+		if x.Cmp(newNumber().SetInt64(0)) == -1 {
+			return nil, ArErr{"Runtime Error", "cannot use factorial on negative number", f.line, f.path, f.code, true}
+		}
+		return fact(x), ArErr{}
+	default:
+		return nil, ArErr{"Runtime Error", "cannot use factorial on non-number of type '" + typeof(val) + "'", f.line, f.path, f.code, true}
+	}
+}