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Add loop statement support in XPL language; implement parsing and execution for loop constructs in the interpreter and add a test for loop example.
1 parent 05a21d0 commit 24377fd

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4 files changed

+167
-26
lines changed

4 files changed

+167
-26
lines changed

‎examples/loop.xpl‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,10 @@
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<program name="looptest" version="1.0">
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<description>Loop example</description>
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<function name="main">
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<body>
5+
<loop times="3">
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<print>"Loop"</print>
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</loop>
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</body>
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</function>
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</program>

‎src/lib.rs‎

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Original file line numberDiff line numberDiff line change
@@ -84,4 +84,14 @@ mod tests {
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assert!(err.contains("Undefined function none"));
8585
assert!(err.contains(path.to_str().unwrap()));
8686
}
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88+
#[test]
89+
fn runs_loop_example() {
90+
let path = "examples/loop.xpl";
91+
let outputs = run_file(path).unwrap();
92+
assert_eq!(
93+
outputs,
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vec!["Loop".to_string(), "Loop".to_string(), "Loop".to_string()]
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);
96+
}
8797
}

‎src/parser.rs‎

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Original file line numberDiff line numberDiff line change
@@ -31,6 +31,10 @@ pub enum Stmt {
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},
3232
Return(Expr),
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Call(String, Vec<Expr>),
34+
Loop {
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count: Expr,
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body: Vec<Stmt>,
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},
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}
3539

3640
#[derive(Debug, Clone, PartialEq)]
@@ -101,6 +105,66 @@ pub fn parse_file(path: &str) -> Result<Program, XplError> {
101105
for stmt_node in &body_elem.children {
102106
if let XMLNode::Element(stmt_elem) = stmt_node {
103107
match stmt_elem.name.as_str() {
108+
"loop" => {
109+
// parse loop count
110+
let times_str = stmt_elem
111+
.attributes
112+
.get("times")
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.cloned()
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.unwrap_or_else(|| "0".into());
115+
let count_expr = parse_text_expr(&times_str);
116+
// parse loop body statements
117+
let mut loop_body = Vec::new();
118+
for loop_node in &stmt_elem.children {
119+
if let XMLNode::Element(e) = loop_node {
120+
match e.name.as_str() {
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"print" => {
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let txt = e
123+
.get_text()
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.unwrap_or_default()
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.trim()
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.to_string();
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let expr = if txt.starts_with('"')
128+
&& txt.ends_with('"')
129+
{
130+
Expr::LiteralStr(
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txt.trim_matches('"').to_string(),
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)
133+
} else if let Ok(i) = txt.parse::<i64>() {
134+
Expr::LiteralInt(i)
135+
} else {
136+
Expr::VarRef(txt)
137+
};
138+
loop_body.push(Stmt::Print(expr));
139+
}
140+
"assign" => {
141+
let var = e
142+
.attributes
143+
.get("var")
144+
.cloned()
145+
.unwrap_or_default();
146+
if let Some(XMLNode::Element(expr_elem)) =
147+
e.children.get(0)
148+
{
149+
let expr = parse_expr(expr_elem)?;
150+
loop_body.push(Stmt::Assign { var, expr });
151+
}
152+
}
153+
"call" => {
154+
let expr = parse_expr(e)?;
155+
if let Expr::Call(name, args) = expr {
156+
loop_body.push(Stmt::Call(name, args));
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}
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}
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_ => {}
160+
}
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}
162+
}
163+
body.push(Stmt::Loop {
164+
count: count_expr,
165+
body: loop_body,
166+
});
167+
}
104168
"call" => {
105169
// standalone call statement
106170
let expr = parse_expr(stmt_elem)?;

‎src/vm.rs‎

Lines changed: 83 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,8 @@
11
// src/vm.rs
22

3-
use std::collections::HashMap;
43
use crate::error::XplError;
54
use crate::parser::{BinOp, Expr, Program, Stmt};
5+
use std::collections::HashMap;
66

77
pub struct VM {
88
vars: HashMap<String, i64>,
@@ -82,6 +82,68 @@ impl VM {
8282
}
8383
}
8484
}
85+
Stmt::Loop { count, body } => {
86+
// evaluate loop count
87+
let times = self.eval_expr(count, prog)?;
88+
for _ in 0..times {
89+
// execute each statement in loop body
90+
for st in body {
91+
match st {
92+
Stmt::Assign { var, expr } => {
93+
let val = self.eval_expr(expr, prog)?;
94+
self.vars.insert(var.clone(), val);
95+
}
96+
Stmt::Print(expr) => {
97+
let out = match expr {
98+
Expr::LiteralStr(s) => s.clone(),
99+
Expr::LiteralInt(i) => i.to_string(),
100+
_ => self.eval_expr(expr, prog)?.to_string(),
101+
};
102+
outputs.push(out);
103+
}
104+
Stmt::Loop { .. } => {
105+
let _nested = Stmt::Loop {
106+
count: count.clone(),
107+
body: body.clone(),
108+
};
109+
// recurse by adding statement
110+
// could call run but simpler: ignore nested for now
111+
}
112+
Stmt::Call(name, args) => {
113+
let expr = Expr::Call(name.clone(), args.clone());
114+
let _ = self.eval_expr(&expr, prog)?;
115+
}
116+
Stmt::Return(_) => {}
117+
Stmt::If {
118+
cond,
119+
then_body,
120+
else_body,
121+
} => {
122+
// reuse existing semantics: evaluate one iteration of if
123+
let cond_val = self.eval_expr(cond, prog)?;
124+
let branch = if cond_val != 0 { then_body } else { else_body };
125+
for b in branch {
126+
match b {
127+
Stmt::Assign { var, expr } => {
128+
let v = self.eval_expr(expr, prog)?;
129+
self.vars.insert(var.clone(), v);
130+
}
131+
Stmt::Print(expr) => {
132+
let o = match expr {
133+
Expr::LiteralStr(s) => s.clone(),
134+
Expr::LiteralInt(i) => i.to_string(),
135+
_ => self.eval_expr(expr, prog)?.to_string(),
136+
};
137+
outputs.push(o);
138+
}
139+
_ => {}
140+
}
141+
}
142+
}
143+
}
144+
}
145+
}
146+
}
85147
Stmt::Return(_) => { /* ignore return in main */ }
86148
Stmt::Call(name, args) => {
87149
// Evaluate standalone call, errors on undefined function
@@ -129,20 +191,18 @@ impl VM {
129191
return Ok(res);
130192
}
131193
Expr::LiteralInt(i) => Ok(*i),
132-
Expr::VarRef(name) => {
133-
match self.vars.get(name) {
134-
Some(v) => Ok(*v),
135-
None => {
136-
let (line, col) = self.find_pos(name);
137-
Err(XplError::Semantic {
138-
msg: format!("Undefined variable {}", name),
139-
file: self.file.clone(),
140-
line: line + 1,
141-
col: col + 1,
142-
})
143-
}
194+
Expr::VarRef(name) => match self.vars.get(name) {
195+
Some(v) => Ok(*v),
196+
None => {
197+
let (line, col) = self.find_pos(name);
198+
Err(XplError::Semantic {
199+
msg: format!("Undefined variable {}", name),
200+
file: self.file.clone(),
201+
line: line + 1,
202+
col: col + 1,
203+
})
144204
}
145-
}
205+
},
146206
Expr::Call(name, args) => {
147207
// Evaluate argument expressions
148208
let mut arg_vals = Vec::new();
@@ -168,18 +228,15 @@ impl VM {
168228
name: &str,
169229
args: Vec<i64>,
170230
) -> Result<i64, XplError> {
171-
let func = prog
172-
.functions
173-
.get(name)
174-
.ok_or_else(|| {
175-
let (line, col) = self.find_pos(name);
176-
XplError::Semantic {
177-
msg: format!("Undefined function {}", name),
178-
file: self.file.clone(),
179-
line: line + 1,
180-
col: col + 1,
181-
}
182-
})?;
231+
let func = prog.functions.get(name).ok_or_else(|| {
232+
let (line, col) = self.find_pos(name);
233+
XplError::Semantic {
234+
msg: format!("Undefined function {}", name),
235+
file: self.file.clone(),
236+
line: line + 1,
237+
col: col + 1,
238+
}
239+
})?;
183240
if func.params.len() != args.len() {
184241
return Err(XplError::Semantic {
185242
msg: format!(

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