Added no_std support

Cargo.toml

@@ -15,14 +15,34 @@ include = [
 ]
 
 [dependencies]
-num-traits = "*"
+num-traits = "0.2.11"
+
+[dependencies.libm]
+version = "0.2.1"
+optional = true
+
+[dependencies.core-error]
+version = "0.0.1-rc4"
+features = ["alloc"]
+optional = true
+
+[dependencies.hashbrown]
+version = "0.7.1"
+default-features = false
+features = ["ahash", "nightly", "inline-more"]
+optional = true
+
+[dependencies.ahash]
+version = "0.3.2"
+default-features = false
+optional = true
 
 [features]
 #default = ["no_function", "no_index", "no_float", "only_i32", "no_stdlib", "unchecked", "no_optimize"]
 default = [ "optimize_full" ]
 debug_msgs = []     # print debug messages on function registrations and calls
 unchecked = []      # unchecked arithmetic
-no_stdlib = []      # no standard library of utility functions
+no_stdlib = ["num-traits/libm", "hashbrown", "core-error", "libm"]      # no standard library of utility functions
 no_index = []       # no arrays and indexing
 no_float = []       # no floating-point
 no_function = []    # no script-defined functions