map on text

README.md

@@ -54,15 +54,18 @@ We also provide some built-in functions:
 * output(path, content): append text content to file path.
 * wasm_profiling(path): load Wasm module, instrument the code and store as a blob value. Calling profiled canister binds the cost to variable `__cost_{id}` or `__cost__`.
 * flamegraph(canister_id, title, filename): generate flamegraph for the last update call to canister_id, with title and write to `{filename}.svg`.
+* concat(e1, e2): concatenate two vec/record/text together.
+* add/sub/mul/div(e1, e2): addition/subtraction/multiplication/division of two integer numbers.
 
 ## Object methods
 
-For `vec` or `record` value, we provide some built-in methods for value transformation:
+For `vec`, `record` or `text` value, we provide some built-in methods for value transformation:
 * v.map(func): transform each item `v[i]` with `func(v[i])`.
 * v.filter(func): filter out item `v[i]` if `func(v[i])` returns `false` or has an error.
 * v.fold(init, func): combine all items in `v` by repeatedly apply `func(...func(func(init, v[0]), v[1])..., v[n-1])`.
 
 For `record` value, `v[i]` is represented as `record { key; value }` sorted by field id.
+for `text` value, `v[i]` is represented as a `text` value containing a single character.
 
 ## Examples
 

examples/func.sh

@@ -21,3 +21,9 @@ function f7(acc, x) { let _ = concat(acc, vec{x[1]}) };
 assert z.filter(f6).map(f5) == record { 1; 2 = 3; 4 }; 
 assert z.filter(f6).map(f5).fold(vec{}, f7) == vec {1;3;4};
 
+let s = "abcdef";
+function f8(x) { let _ = stringify(" ", x) };
+function f9(acc, x) { let _ = add(acc, 1) };
+assert s.map(f8) == " a b c d e f";
+assert s.map(f8).fold(0, f9) == 12;
+

src/selector.rs

@@ -61,6 +61,20 @@ pub fn project(helper: &MyHelper, value: IDLValue, path: Vec<Selector>) -> Resul
                 let vs = from_fields(fs);
                 result = fold(helper, init, vs, &func)?;
             }
+            (IDLValue::Text(s), Selector::Map(func)) => {
+                let vs = from_text(s);
+                let res = map(helper, vs, &func)?;
+                result = IDLValue::Text(to_text(res)?);
+            }
+            (IDLValue::Text(s), Selector::Filter(func)) => {
+                let vs = from_text(s);
+                let res = filter(helper, vs, &func)?;
+                result = IDLValue::Text(to_text(res)?);
+            }
+            (IDLValue::Text(s), Selector::Fold(init, func)) => {
+                let vs = from_text(s);
+                result = fold(helper, init, vs, &func)?;
+            }
             (IDLValue::Record(fs), field @ (Selector::Index(_) | Selector::Field(_))) => {
                 let id = field.to_label();
                 if let Some(v) = fs.into_iter().find(|f| f.id == id) {
@@ -107,7 +121,21 @@ fn from_fields(fs: Vec<IDLField>) -> Vec<IDLValue> {
         })
         .collect()
 }
-
+fn from_text(s: String) -> Vec<IDLValue> {
+    s.chars().map(|c| IDLValue::Text(c.to_string())).collect()
+}
+fn to_text(from: Vec<IDLValue>) -> Result<String> {
+    use std::fmt::Write;
+    let mut res = String::with_capacity(from.len());
+    for v in from.into_iter() {
+        if let IDLValue::Text(s) = v {
+            write!(&mut res, "{}", s)?;
+        } else {
+            return Err(anyhow!("expect function to return text"));
+        }
+    }
+    Ok(res)
+}
 fn to_field(from: Vec<IDLValue>) -> Result<Vec<IDLField>> {
     let mut fs = Vec::with_capacity(from.len());
     for v in from.into_iter() {
@@ -126,9 +154,9 @@ fn to_field(from: Vec<IDLValue>) -> Result<Vec<IDLField>> {
                         val: val.clone(),
                     })
                 }
-                _ => return Err(anyhow!("map doesn't return record {{ key; value }}")),
+                _ => return Err(anyhow!("expect function to return record {{ key; value }}")),
             },
-            _ => return Err(anyhow!("map doesn't return record {{ key; value }}")),
+            _ => return Err(anyhow!("expect function to return record {{ key; value }}")),
         }
     }
     fs.sort_unstable_by_key(|IDLField { id, .. }| id.get_id());