random-float and random-int added

lib/src/metta/runner/stdlib.metta

@@ -422,6 +422,20 @@
     (@param "Index")))
   (@return "Atom from an expression in the place defined by index. Error if index is out of bounds of an expression"))
 
+(@doc random-int
+  (@desc "Returns random int number from range defined by two numbers (first and second argument)")
+  (@params (
+    (@param "Range start")
+    (@param "Range end")))
+  (@return "Random int number from defined range"))
+
+(@doc random-float
+  (@desc "Returns random float number from range defined by two numbers (first and second argument)")
+  (@params (
+    (@param "Range start")
+    (@param "Range end")))
+  (@return "Random float number from defined range"))
+
 (@doc println!
   (@desc "Prints a line of text to the console")
   (@params (

lib/src/metta/runner/stdlib.rs

@@ -21,6 +21,7 @@ use std::cell::RefCell;
 use std::fmt::Display;
 use std::collections::HashMap;
 use regex::Regex;
+use rand::Rng;
 
 use super::arithmetics::*;
 use super::string::*;
@@ -1253,6 +1254,70 @@ impl CustomExecute for SubtractionAtomOp {
     }
 }
 
+
+//TODO: In the current version of rand it is possible for rust to hang if range end's value is too
+// big. In future releases (0.9+) of rand signature of sample_single will be changed and it will be
+// possible to use match construction to cover overflow and other errors. So after library will be
+// upgraded RandomInt and RandomFloat codes should be altered.
+// see comment https://github.com/trueagi-io/hyperon-experimental/pull/791#discussion_r1824355414
+#[derive(Clone, Debug)]
+pub struct RandomIntOp {}
+
+grounded_op!(RandomIntOp, "random-int");
+
+impl Grounded for RandomIntOp {
+    fn type_(&self) -> Atom {
+        Atom::expr([ARROW_SYMBOL, ATOM_TYPE_NUMBER, ATOM_TYPE_NUMBER, ATOM_TYPE_NUMBER])
+    }
+
+    fn as_execute(&self) -> Option<&dyn CustomExecute> {
+        Some(self)
+    }
+}
+
+impl CustomExecute for RandomIntOp {
+    fn execute(&self, args: &[Atom]) -> Result<Vec<Atom>, ExecError> {
+        let arg_error = || ExecError::from("random-int expects two arguments: number (start) and number (end)");
+        let start: i64 = AsPrimitive::from_atom(args.get(0).ok_or_else(arg_error)?).as_number().ok_or_else(arg_error)?.into();
+        let end: i64 = AsPrimitive::from_atom(args.get(1).ok_or_else(arg_error)?).as_number().ok_or_else(arg_error)?.into();
+        let range = start..end;
+        if range.is_empty() {
+            return Err(ExecError::from("Range is empty"));
+        }
+        let mut rng = rand::thread_rng();
+        Ok(vec![Atom::gnd(Number::Integer(rng.gen_range(range)))])
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct RandomFloatOp {}
+
+grounded_op!(RandomFloatOp, "random-float");
+
+impl Grounded for RandomFloatOp {
+    fn type_(&self) -> Atom {
+        Atom::expr([ARROW_SYMBOL, ATOM_TYPE_NUMBER, ATOM_TYPE_NUMBER, ATOM_TYPE_NUMBER])
+    }
+
+    fn as_execute(&self) -> Option<&dyn CustomExecute> {
+        Some(self)
+    }
+}
+
+impl CustomExecute for RandomFloatOp {
+    fn execute(&self, args: &[Atom]) -> Result<Vec<Atom>, ExecError> {
+        let arg_error = || ExecError::from("random-float expects two arguments: number (start) and number (end)");
+        let start: f64 = AsPrimitive::from_atom(args.get(0).ok_or_else(arg_error)?).as_number().ok_or_else(arg_error)?.into();
+        let end: f64 = AsPrimitive::from_atom(args.get(1).ok_or_else(arg_error)?).as_number().ok_or_else(arg_error)?.into();
+        let range = start..end;
+        if range.is_empty() {
+            return Err(ExecError::from("Range is empty"));
+        }
+        let mut rng = rand::thread_rng();
+        Ok(vec![Atom::gnd(Number::Float(rng.gen_range(range)))])
+    }
+}
+
 /// The internal `non_minimal_only_stdlib` module contains code that is never used by the minimal stdlib
 #[cfg(feature = "old_interpreter")]
 mod non_minimal_only_stdlib {
@@ -1766,6 +1831,10 @@ mod non_minimal_only_stdlib {
         tref.register_token(regex(r"cons-atom"), move |_| { cons_atom_op.clone() });
         let index_atom_op = Atom::gnd(IndexAtomOp{});
         tref.register_token(regex(r"index-atom"), move |_| { index_atom_op.clone() });
+        let random_int_op = Atom::gnd(RandomIntOp{});
+        tref.register_token(regex(r"random-int"), move |_| { random_int_op.clone() });
+        let random_float_op = Atom::gnd(RandomFloatOp{});
+        tref.register_token(regex(r"random-float"), move |_| { random_float_op.clone() });
         let println_op = Atom::gnd(PrintlnOp{});
         tref.register_token(regex(r"println!"), move |_| { println_op.clone() });
         let format_args_op = Atom::gnd(FormatArgsOp{});
@@ -2061,6 +2130,23 @@ mod tests {
         assert_eq!(res, Err(ExecError::from("Index is out of bounds")));
     }
 
+    #[test]
+    fn random_op() {
+        let res = RandomIntOp{}.execute(&mut vec![expr!({Number::Integer(0)}), expr!({Number::Integer(5)})]);
+        let range = 0..5;
+        let res_i64: i64 = AsPrimitive::from_atom(res.unwrap().get(0).unwrap()).as_number().unwrap().into();
+        assert!(range.contains(&res_i64));
+        let res = RandomIntOp{}.execute(&mut vec![expr!({Number::Integer(2)}), expr!({Number::Integer(-2)})]);
+        assert_eq!(res, Err(ExecError::from("Range is empty")));
+
+        let res = RandomFloatOp{}.execute(&mut vec![expr!({Number::Integer(0)}), expr!({Number::Integer(5)})]);
+        let range = 0.0..5.0;
+        let res_f64: f64 = AsPrimitive::from_atom(res.unwrap().get(0).unwrap()).as_number().unwrap().into();
+        assert!(range.contains(&res_f64));
+        let res = RandomFloatOp{}.execute(&mut vec![expr!({Number::Integer(0)}), expr!({Number::Integer(0)})]);
+        assert_eq!(res, Err(ExecError::from("Range is empty")));
+    }
+
     #[test]
     fn bind_new_space_op() {
         let tokenizer = Shared::new(Tokenizer::new());

lib/src/metta/runner/stdlib_minimal.metta

@@ -79,6 +79,20 @@
     (@param "Index")))
   (@return "Atom from an expression in the place defined by index. Error if index is out of bounds"))
 
+(@doc random-int
+  (@desc "Returns random int number from range defined by two numbers (first and second argument)")
+  (@params (
+    (@param "Range start")
+    (@param "Range end")))
+  (@return "Random int number from defined range"))
+
+(@doc random-float
+  (@desc "Returns random float number from range defined by two numbers (first and second argument)")
+  (@params (
+    (@param "Range start")
+    (@param "Range end")))
+  (@return "Random float number from defined range"))
+
 (@doc collapse-bind
   (@desc "Evaluates minimal MeTTa operation (first argument) and returns an expression which contains all alternative evaluations in a form (Atom Bindings). Bindings are represented in a form of a grounded atom.")
   (@params (

lib/src/metta/runner/stdlib_minimal.rs

@@ -434,6 +434,10 @@ pub fn register_common_tokens(tref: &mut Tokenizer, _tokenizer: Shared<Tokenizer
     tref.register_token(regex(r"match"), move |_| { match_op.clone() });
     let index_atom_op = Atom::gnd(stdlib::IndexAtomOp{});
     tref.register_token(regex(r"index-atom"), move |_| { index_atom_op.clone() });
+    let random_int_op = Atom::gnd(stdlib::RandomIntOp{});
+    tref.register_token(regex(r"random-int"), move |_| { random_int_op.clone() });
+    let random_float_op = Atom::gnd(stdlib::RandomFloatOp{});
+    tref.register_token(regex(r"random-float"), move |_| { random_float_op.clone() });
     let mod_space_op = Atom::gnd(stdlib::ModSpaceOp::new(metta.clone()));
     tref.register_token(regex(r"mod-space!"), move |_| { mod_space_op.clone() });
     let print_mods_op = Atom::gnd(stdlib::PrintModsOp::new(metta.clone()));
@@ -623,6 +627,14 @@ mod tests {
         assert_eq!(run_program(&format!("!(index-atom (A B C D E) 5)")), Ok(vec![vec![expr!("Error" ({ stdlib::IndexAtomOp{} } ("A" "B" "C" "D" "E") {Number::Integer(5)}) "Index is out of bounds")]]));
     }
 
+    #[test]
+    fn metta_random() {
+        assert_eq!(run_program(&format!("!(chain (eval (random-int 0 5)) $rint (and (>= $rint 0) (< $rint 5)))")), Ok(vec![vec![expr!({Bool(true)})]]));
+        assert_eq!(run_program(&format!("!(random-int 0 0)")), Ok(vec![vec![expr!("Error" ({ stdlib::RandomIntOp{} } {Number::Integer(0)} {Number::Integer(0)}) "Range is empty")]]));
+        assert_eq!(run_program(&format!("!(chain (eval (random-float 0.0 5.0)) $rfloat (and (>= $rfloat 0.0) (< $rfloat 5.0)))")), Ok(vec![vec![expr!({Bool(true)})]]));
+        assert_eq!(run_program(&format!("!(random-float 0 -5)")), Ok(vec![vec![expr!("Error" ({ stdlib::RandomFloatOp{} } {Number::Integer(0)} {Number::Integer(-5)}) "Range is empty")]]));
+    }
+
     #[test]
     fn metta_switch() {
         let result = run_program("!(eval (switch (A $b) ( (($a B) ($b $a)) ((B C) (C B)) )))");