Initial project import

tools/v/examples/call_v_from_python/README.md

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+A simple example to show how to call a function written in v from python
+
+Step 1: Compile the v code to a shared library using `v -d no_backtrace -shared test.v`
+
+Step 2: Run the python file using `python3 test.py`
+
+Note: you do not need `-d no_backtrace` if you use gcc or clang .

tools/v/examples/call_v_from_python/test.py

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+from ctypes import *
+import math, os
+
+## Load the V shared library:
+so_file="./test.so"
+if os.name=="nt":
+  so_file="./test.dll"
+lib = CDLL(so_file)
+
+## Pass an integer to a V function, and receiving back an integer:
+print("lib.square(10) result is", lib.square(10))
+assert lib.square(10) == 100, "Cannot validate V square()."
+
+## Pass a floating point number to a V function:
+lib.sqrt_of_sum_of_squares.restype = c_double
+assert lib.sqrt_of_sum_of_squares(c_double(1.1), c_double(2.2)) == math.sqrt(1.1*1.1 + 2.2*2.2), "Cannot validate V sqrt_of_sum_of_squares()."
+
+## Passing a V string to a V function, and receiving back a V string:
+class VString(Structure):
+  _fields_ = [("str", c_char_p), ("len", c_int)]
+
+lib.process_v_string.argtypes = [VString]
+lib.process_v_string.restype = VString
+
+assert lib.process_v_string(VString(b'World', 5)).str == b'v World v'
+print('Hello', str(lib.process_v_string(VString(b'World', 5)).str, 'utf-8'))

tools/v/examples/call_v_from_python/test.v

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+// vtest build: present_python? // the example only makes sense to be compiled, when python is installed
+module test
+
+// Note: compile this with `v -d no_backtrace -shared test.v`
+import math
+
+@[export: 'square']
+fn square(i int) int {
+	return i * i
+}
+
+@[export: 'sqrt_of_sum_of_squares']
+fn sqrt_of_sum_of_squares(x f64, y f64) f64 {
+	return math.sqrt(x * x + y * y)
+}
+
+// you do not have to use the same name in the export attribute
+@[export: 'process_v_string']
+fn work(s string) string {
+	return 'v ${s} v'
+}