add readme.md for github

README.md

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+[![Build Status](https://travis-ci.org/n0la/libdice.svg?branch=master)](https://travis-ci.org/n0la/libdice)
+
+**Warning: The API is not yet stable**
+
+# libdice
+
+``libdice`` is a small C library for rolling P&P style dice and for
+evaluating dice expressions.
+
+## Features
+
+* Written in ANSI C99
+* Uses solid and reliable RNG, no need for seeding
+* Mathematic expression library for advanced dice rolling
+
+## Dice syntax
+
+Currently the supported syntax in ``libdice`` is rather limited. It only
+supports variable amount and variable sides at the moment:
+
+* Roll four six sided dices: ``4d6``
+* Roll one twenty sided die: ``d20``
+
+## Build
+
+``libdice`` requires:
+
+* libbsd
+* bison
+* flex
+* cmocka >= 1.0.1
+
+To build ``libdice`` run:
+
+```shell
+$ ./configure --prefix="/usr"
+$ make
+$ sudo make install
+```
+
+## Dice API
+
+The core api relies on ``dice_new`` which creates a new dice (or a set of dice),
+which is then freed by ``dice_free``. Dice can be initialised through the proper
+``dice_set`` function, or by using either ``dice_simple`` or ``dice_parse``:
+
+```C
+#include <dice.h>
+
+dice_t d = dice_new();
+
+dice_set(d, DICEOPTION_AMOUNT, 4);
+dice_set(d, DICEOPTION_SIDES, 6);
+
+/* or simpler:
+ * d = dice_simple(4, 6);
+ */
+
+
+printf("%ld\n", dice_roll(d));
+dice_free(d);
+```
+
+There is also an easier API:
+
+```C
+dice_t d20 = dice_simple(1, 20);
+
+printf("%ld\n", dice_roll(d20));
+dice_free(d20);
+```
+
+And a more advanced API:
+
+```C
+dice_t d = dice_simple(4, 6);
+dice_result_t *res = NULL;
+size_t reslen = 0, i = 0;
+
+if (!dice_evaluate(d, &res, &reslen)) {
+    goto fail;
+}
+
+for (; i < reslen; i++) {
+    printf("%ld\n", res[i].result);
+}
+
+fail:
+dice_result_freev(res, reslen);
+dice_free(d);
+```
+
+You can also parse dice strings:
+
+```C
+dice_t d20 = dice_new();
+
+if (!dice_parse(d20, "5d20")) {
+   char const *err = NULL;
+   dice_get(d20, DICEOPTION_ERROR, &err);
+   fprintf(stderr, "error: %s\n", err);
+}
+
+printf("%ld\n", dice_roll(d20));
+dice_free(d20);
+```
+
+## Expression API
+
+The expression API supports multiple die within one mathematical expression.
+Expressions are parsed using [tinyexpr](https://github.com/codeplea/tinyexpr)
+library.
+
+```C
+int error = 0;
+char const *expr = "1d20+8+4+3-1";
+dice_expression_t e = dice_expression_parse(expr, &err);
+int64_t result = 0;
+
+if (e == NULL) {
+    fprintf(stderr, "error in expression: \"%s\": at %d\n", expr, err);
+    goto fail;
+}
+
+if (!dice_expression_evaluate(e, &result)) {
+    goto fail;
+}
+
+printf("%ld\n", result);
+
+fail:
+dice_expression_free(e);
+```
+
+## Copyright
+
+``libdice`` is dual licenced. The ``tinyexpr`` is licenced under the zlib
+licence (see COPYING.tinyexpr), and the rest of ``libdice`` is available under
+the LGPLv3.