//: Structured programming
//:
//: Our jump recipes are quite inconvenient to use, so mu provides a
//: lightweight tool called 'transform_braces' to work in a slightly more
//: convenient format with nested braces:
//:
//: {
//: some instructions
//: {
//: more instructions
//: }
//: }
//:
//: Braces are just labels, they require no special parsing. The pseudo
//: recipes 'loop' and 'break' jump to just after the enclosing '{' and '}'
//: respectively.
//:
//: Conditional and unconditional 'loop' and 'break' should give us 80% of the
//: benefits of the control-flow primitives we're used to in other languages,
//: like 'if', 'while', 'for', etc.
:(scenarios transform)
:(scenario brace_conversion)
recipe main [
{
break
1:number <- copy 0
}
]
+after-brace: recipe main
+after-brace: jump 1:offset
+after-brace: copy ...
//: one-time setup
:(after "int main")
Transform.push_back(transform_braces);
:(code)
void transform_braces(const recipe_ordinal r) {
//? cout << "AAA transform_braces\n"; //? 1
//? exit(0); //? 1
const int OPEN = 0, CLOSE = 1;
// use signed integer for step index because we'll be doing arithmetic on it
list<pair<int/*OPEN/CLOSE*/, /*step*/long long int> > braces;
for (long long int index = 0; index < SIZE(Recipe[r].steps); ++index) {
const instruction& inst = Recipe[r].steps.at(index);
if (inst.label == "{") {
trace("brace") << r << ": push (open, " << index << ")" << end();
braces.push_back(pair<int,long long int>(OPEN, index));
}
if (inst.label == "}") {
trace("brace") << "push (close, " << index << ")" << end();
braces.push_back(pair<int,long long int>(CLOSE, index));
}
}
stack</*step*/long long int> open_braces;
trace("after-brace") << "recipe " << Recipe[r].name << end();
for (long long int index = 0; index < SIZE(Recipe[r].steps); ++index) {
instruction& inst = Recipe[r].steps.at(index);
if (inst.label == "{") {
open_braces.push(index);
continue;
}
if (inst.label == "}") {
open_braces.pop();
continue;
}
if (inst.is_label) continue;
if (inst.operation != Recipe_ordinal["loop"]
&& inst.operation != Recipe_ordinal["loop-if"]
&& inst.operation != Recipe_ordinal["loop-unless"]
&& inst.operation != Recipe_ordinal["break"]
&& inst.operation != Recipe_ordinal["break-if"]
&& inst.operation != Recipe_ordinal["break-unless"]) {
trace("after-brace") << inst.name << " ..." << end();
continue;
}
// update instruction operation
if (inst.name.find("-if") != string::npos)
inst.operation = Recipe_ordinal["jump-if"];
else if (inst.name.find("-unless") != string::npos)
inst.operation = Recipe_ordinal["jump-unless"];
else
inst.operation = Recipe_ordinal["jump"];
// check for explicitly provided targets
if (inst.name.find("-if") != string::npos || inst.name.find("-unless") != string::npos) {
// conditional branches check arg 1
if (SIZE(inst.ingredients) > 1 && is_literal(inst.ingredients.at(1))) {
trace("after-brace") << "jump " << inst.ingredients.at(1).name << ":offset" << end();
continue;
}
}
else {
// unconditional branches check arg 0
if (!inst.ingredients.empty() && is_literal(inst.ingredients.at(0))) {
trace("after-brace") << "jump " << inst.ingredients.at(0).name << ":offset" << end();
continue;
}
}
// if implicit, compute target
reagent target;
target.types.push_back(Type_ordinal["offset"]);
target.set_value(0);
if (open_braces.empty())
raise << inst.name << " needs a '{' before\n" << end();
else if (inst.name.find("loop") != string::npos)
target.set_value(open_braces.top()-index);
else // break instruction
target.set_value(matching_brace(open_braces.top(), braces, r) - index - 1);
inst.ingredients.push_back(target);
// log computed target
if (inst.name.find("-if") != string::npos)
trace("after-brace") << "jump-if " << inst.ingredients.at(0).name << ", " << target.value << ":offset" << end();
else if (inst.name.find("-unless") != string::npos)
trace("after-brace") << "jump-unless " << inst.ingredients.at(0).name << ", " << target.value << ":offset" << end();
else
trace("after-brace") << "jump " << target.value << ":offset" << end();
}
}
// returns a signed integer not just so that we can return -1 but also to
// enable future signed arithmetic
long long int matching_brace(long long int index, const list<pair<int, long long int> >& braces, recipe_ordinal r) {
int stacksize = 0;
for (list<pair<int, long long int> >::const_iterator p = braces.begin(); p != braces.end(); ++p) {
if (p->second < index) continue;
stacksize += (p->first ? 1 : -1);
if (stacksize == 0) return p->second;
}
raise << Recipe[r].name << ": unbalanced '{'\n" << end();
return SIZE(Recipe[r].steps); // exit current routine
}
// temporarily suppress run
void transform(string form) {
load(form);
transform_all();
}
//: Make sure these pseudo recipes get consistent numbers in all tests, even
//: though they aren't implemented.
:(before "End Primitive Recipe Declarations")
BREAK,
BREAK_IF,
BREAK_UNLESS,
LOOP,
LOOP_IF,
LOOP_UNLESS,
:(before "End Primitive Recipe Numbers")
Recipe_ordinal["break"] = BREAK;
Recipe_ordinal["break-if"] = BREAK_IF;
Recipe_ordinal["break-unless"] = BREAK_UNLESS;
Recipe_ordinal["loop"] = LOOP;
Recipe_ordinal["loop-if"] = LOOP_IF;
Recipe_ordinal["loop-unless"] = LOOP_UNLESS;
:(scenario loop)
recipe main [
1:number <- copy 0
2:number <- copy 0
{
3:number <- copy 0
loop
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: copy ...
+after-brace: copy ...
+after-brace: jump -2:offset
:(scenario break_empty_block)
recipe main [
1:number <- copy 0
{
break
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: jump 0:offset
:(scenario break_cascading)
recipe main [
1:number <- copy 0
{
break
}
{
break
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: jump 0:offset
+after-brace: jump 0:offset
:(scenario break_cascading2)
recipe main [
1:number <- copy 0
2:number <- copy 0
{
break
3:number <- copy 0
}
{
break
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: copy ...
+after-brace: jump 1:offset
+after-brace: copy ...
+after-brace: jump 0:offset
:(scenario break_if)
recipe main [
1:number <- copy 0
2:number <- copy 0
{
break-if 2:number
3:number <- copy 0
}
{
break
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: copy ...
+after-brace: jump-if 2, 1:offset
+after-brace: copy ...
+after-brace: jump 0:offset
:(scenario break_nested)
recipe main [
1:number <- copy 0
{
2:number <- copy 0
break
{
3:number <- copy 0
}
4:number <- copy 0
}
]
+after-brace: jump 4:offset
:(scenario break_nested_degenerate)
recipe main [
1:number <- copy 0
{
2:number <- copy 0
break
{
}
4:number <- copy 0
}
]
+after-brace: jump 3:offset
:(scenario break_nested_degenerate2)
recipe main [
1:number <- copy 0
{
2:number <- copy 0
break
{
}
}
]
+after-brace: jump 2:offset
:(scenario break_label)
% Hide_warnings = true;
recipe main [
1:number <- copy 0
{
break +foo:offset
}
]
+after-brace: jump +foo:offset
:(scenario break_unless)
recipe main [
1:number <- copy 0
2:number <- copy 0
{
break-unless 2:number
3:number <- copy 0
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: copy ...
+after-brace: jump-unless 2, 1:offset
+after-brace: copy ...
:(scenario loop_unless)
recipe main [
1:number <- copy 0
2:number <- copy 0
{
loop-unless 2:number
3:number <- copy 0
}
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: copy ...
+after-brace: jump-unless 2, -1:offset
+after-brace: copy ...
:(scenario loop_nested)
recipe main [
1:number <- copy 0
{
2:number <- copy 0
{
3:number <- copy 0
}
loop-if 4:boolean
5:number <- copy 0
}
]
+after-brace: recipe main
+after-brace: jump-if 4, -5:offset
:(scenario loop_label)
recipe main [
1:number <- copy 0
+foo
2:number <- copy 0
]
+after-brace: recipe main
+after-brace: copy ...
+after-brace: copy ...
//: test how things actually run
:(scenarios run)
:(scenario brace_conversion_and_run)
#? % Trace_stream->dump_layer = "run";
recipe test-factorial [
1:number <- copy 5
2:number <- copy 1
{
3:boolean <- equal 1:number, 1
break-if 3:boolean
# $print 1:number
2:number <- multiply 2:number, 1:number
1:number <- subtract 1:number, 1
loop
}
4:number <- copy 2:number # trigger a read
]
+mem: location 2 is 120
:(scenario break_outside_braces_warns)
% Hide_warnings = true;
recipe main [
break
]
+warn: break needs a '{' before