From 94fe42391cb9465c9717ad4f337d053bd7c8afeb Mon Sep 17 00:00:00 2001
From: chendotjs <chendotjs@qq.com>
Date: Wed, 15 Mar 2017 18:25:37 +0800
Subject: [PATCH] add fac and infs/combinatoric test

---
 test.c     | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tinyexpr.c | 21 +++++++++++++++++++
 2 files changed, 81 insertions(+)

diff --git a/test.c b/test.c
index b86a83f..82611eb 100644
--- a/test.c
+++ b/test.c
@@ -213,6 +213,7 @@ void test_nans() {
         "1%0",
         "1%(1%0)",
         "(1%0)%1",
+        "fac(-1)",
     };
 
     int i;
@@ -234,6 +235,34 @@ void test_nans() {
 }
 
 
+void test_infs() {
+
+    const char *infs[] = {
+            "1/0",
+            "log(0)",
+            "pow(2,10000000)",
+            "fac(300)",
+    };
+
+    int i;
+    for (i = 0; i < sizeof(infs) / sizeof(const char *); ++i) {
+        const char *expr = infs[i];
+
+        int err;
+        const double r = te_interp(expr, &err);
+        lequal(err, 0);
+        lok(r == r + 1);
+
+        te_expr *n = te_compile(expr, 0, 0, &err);
+        lok(n);
+        lequal(err, 0);
+        const double c = te_eval(n);
+        lok(c == c + 1);
+        te_free(n);
+    }
+}
+
+
 void test_variables() {
 
     double x, y, test;
@@ -587,17 +616,48 @@ void test_pow() {
 
 }
 
+void test_combinatorics() {
+    test_case cases[] = {
+            {"fac(0) ", 1},
+            {"fac(0.2) ", 1},
+            {"fac(1) ", 1},
+            {"fac(2) ", 2},
+            {"fac(3) ", 6},
+            {"fac(4.8) ", 24},
+            {"fac(10) ", 3628800},
+    };
+
+
+    int i;
+    for (i = 0; i < sizeof(cases) / sizeof(test_case); ++i) {
+        const char *expr = cases[i].expr;
+        const double answer = cases[i].answer;
+
+        int err;
+        const double ev = te_interp(expr, &err);
+        lok(!err);
+        lfequal(ev, answer);
+
+        if (err) {
+            printf("FAILED: %s (%d)\n", expr, err);
+        }
+    }
+}
+
+
 int main(int argc, char *argv[])
 {
     lrun("Results", test_results);
     lrun("Syntax", test_syntax);
     lrun("NaNs", test_nans);
+    lrun("INFs", test_infs);
     lrun("Variables", test_variables);
     lrun("Functions", test_functions);
     lrun("Dynamic", test_dynamic);
     lrun("Closure", test_closure);
     lrun("Optimize", test_optimize);
     lrun("Pow", test_pow);
+    lrun("Combinatorics", test_combinatorics);
     lresults();
 
     return lfails != 0;
diff --git a/tinyexpr.c b/tinyexpr.c
index e6b61dc..f2a6175 100755
--- a/tinyexpr.c
+++ b/tinyexpr.c
@@ -39,11 +39,17 @@ For log = natural log uncomment the next line. */
 #include <math.h>
 #include <string.h>
 #include <stdio.h>
+#include <limits.h>
 
 #ifndef NAN
 #define NAN (0.0/0.0)
 #endif
 
+#ifndef INFINITY
+#define INFINITY (1.0/0.0)
+#endif
+
+
 typedef double (*te_fun2)(double, double);
 
 enum {
@@ -113,6 +119,20 @@ void te_free(te_expr *n) {
 
 static double pi() {return 3.14159265358979323846;}
 static double e() {return 2.71828182845904523536;}
+static double fac(double a) {/* simplest version of fac */
+    if (a < 0.0)
+        return NAN;
+    if (a > UINT_MAX)
+        return INFINITY;
+    unsigned int ua = (unsigned int)(a);
+    unsigned long int result = 1, i = 1;
+    for (i = 1; i <= ua; i++) {
+        if (ua > ULONG_MAX / result)
+            return INFINITY;
+        result *= i;
+    }
+    return (double)result;
+}
 
 static const te_variable functions[] = {
     /* must be in alphabetical order */
@@ -126,6 +146,7 @@ static const te_variable functions[] = {
     {"cosh", cosh,    TE_FUNCTION1 | TE_FLAG_PURE, 0},
     {"e", e,          TE_FUNCTION0 | TE_FLAG_PURE, 0},
     {"exp", exp,      TE_FUNCTION1 | TE_FLAG_PURE, 0},
+    {"fac", fac,      TE_FUNCTION1 | TE_FLAG_PURE, 0},
     {"floor", floor,  TE_FUNCTION1 | TE_FLAG_PURE, 0},
     {"ln", log,       TE_FUNCTION1 | TE_FLAG_PURE, 0},
 #ifdef TE_NAT_LOG