try to build strings from list as potential matches in SwitchOnConstant (#623)

Cargo.lock

@@ -51,6 +51,12 @@ version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b41b7ea54a0c9d92199de89e20e58d49f02f8e699814ef3fdf266f6f748d15c7"
 
+[[package]]
+name = "base64"
+version = "0.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3441f0f7b02788e948e47f457ca01f1d7e6d92c693bc132c22b087d3141c03ff"
+
 [[package]]
 name = "bit-set"
 version = "0.5.2"
@@ -1157,7 +1163,7 @@ version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2bc8af4bda8e1ff4932523b94d3dd20ee30a87232323eda55903ffd71d2fb017"
 dependencies = [
- "base64",
+ "base64 0.11.0",
  "blake2b_simd",
  "constant_time_eq",
  "crossbeam-utils",
@@ -1217,6 +1223,7 @@ checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 name = "scryer-prolog"
 version = "0.8.126"
 dependencies = [
+ "base64 0.12.3",
  "blake2",
  "chrono",
  "cpu-time",

src/machine/machine_indices.rs

@@ -272,9 +272,8 @@ impl Addr {
             &Addr::Float(f) => {
                 Some(Constant::Float(f))
             }
-            &Addr::PStrLocation(h, n) => {
+            addr @ &Addr::PStrLocation(..) | addr @ &Addr::Lis(_) => {
-                let mut heap_pstr_iter =
+                let mut heap_pstr_iter = machine_st.heap_pstr_iter(*addr);
-                    machine_st.heap_pstr_iter(Addr::PStrLocation(h, n));
 
                 let buf = heap_pstr_iter.to_string();
                 let end_addr = heap_pstr_iter.focus();