Add 'gap' modifier from Uiua

primitives.md

@@ -43,6 +43,7 @@
 | `self` | `'` |  Call a function with two copies of the same value |
 | `flip` | `"` |  Call a function with its arguments reversed |
 | `dip` | `,` |  Temporarily pop a value from the stack |
+| `gap` | `;` |  Pop a value from the stack |
 | `on` | `o` |  Keep the first argument of a function on top of the stack |
 | `by` | `q` |  Keep the last argument of a function below its outputs on the stack |
 | `both` | `&` |  Call the same function on two sets of arguments |

src/primitive.rs

@@ -74,6 +74,8 @@ prim!(Mod,
     (Flip, "flip", '"'),
     /// Temporarily pop a value from the stack
     (Dip, "dip", ','),
+    /// Pop a value from the stack
+    (Gap, "gap", ';'),
     /// Keep the first argument of a function on top of the stack
     (On, "on", 'o'),
     /// Keep the last argument of a function below its outputs on the stack

src/runtime.rs

@@ -144,6 +144,10 @@ impl Ufel {
                 self.exec(f.node)?;
                 self.stack.push(a?);
             }
+            Mod::Gap => {
+                let _ = self.pop(1);
+                self.exec(f.node)?;
+            }
             Mod::On => {
                 let a = self.pop(1)?;
                 self.push(a.clone());

src/tree.rs

@@ -314,6 +314,7 @@ impl Node {
                     Node::Mod(m, f, _) => match m {
                         Mod::Turn | Mod::Fold => self.handle(f.sig.args, f.sig.outputs),
                         Mod::Dip => self.handle(f.sig.args + 1, f.sig.outputs + 1),
+                        Mod::Gap => self.handle(f.sig.args + 1, f.sig.outputs),
                         Mod::Reduce | Mod::Scan => self.handle(1, 1),
                         Mod::Slf => {
                             self.handle(1, 2);