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Added "case-of" control structure

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This commit is contained in:
Twan van Laarhoven
2020-05-09 18:38:25 +02:00
parent 0a0dd72e36
commit 420c329bc4
5 changed files with 98 additions and 24 deletions
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src/script/parser.cpp
+50 -8
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@@ -381,11 +381,12 @@ enum Precedence
, PREC_NONE
};
/// Type of expressions. Broadly: LHS/exprssion/statement
/// Type of expressions. Broadly: LHS/expression/statement
/// Lower is more restrictive
enum ExprType
{ EXPR_VAR // A single variable, which could be converted to the left hand side of an assignment
, EXPR_STATEMENT // A 'statement', i.e. an expression that doesn't produce a result, and shouldn't be the last one in a block
, EXPR_OTHER
, EXPR_STATEMENT // A 'statement', i.e. an expression that doesn't produce a result, and shouldn't be the last one in a block
, EXPR_FAILED
};
@@ -508,10 +509,10 @@ ExprType parseExpr(TokenIterator& input, Script& script, Precedence minPrec) {
} else if (token == _("if")) {
// if AAA then BBB else CCC
parseOper(input, script, PREC_AND); // AAA
unsigned jmpElse = script.addInstruction(I_JUMP_IF_NOT); // jnz lbl_else
Addr jmpElse = script.addInstruction(I_JUMP_IF_NOT); // jnz lbl_else
expectToken(input, _("then")); // then
ExprType type1 = parseOper(input, script, PREC_SET); // BBB
unsigned jmpEnd = script.addInstruction(I_JUMP); // jump lbl_end
Addr jmpEnd = script.addInstruction(I_JUMP); // jump lbl_end
script.comeFrom(jmpElse); // lbl_else:
ExprType type2 = EXPR_STATEMENT;
if (input.peek() == _("else")) { // else
@@ -520,8 +521,49 @@ ExprType parseExpr(TokenIterator& input, Script& script, Precedence minPrec) {
} else {
script.addInstruction(I_PUSH_CONST, script_nil);
}
script.comeFrom(jmpEnd); // lbl_end:
script.comeFrom(jmpEnd); // lbl_end:
return type1 == EXPR_STATEMENT || type2 == EXPR_STATEMENT ? EXPR_STATEMENT : EXPR_OTHER;
} else if (token == _("case")) {
// case AAA of BBB: CCC[,] DDD: EEE ... else FFF
parseOper(input, script, PREC_AND);
expectToken(input, _("of"));
vector<Addr> jmpsEnd;
bool wasElse = false;
ExprType type = EXPR_OTHER;
Token t = input.peek();
while (t != TOK_RPAREN && t != TOK_EOF) {
Addr jmp;
if (input.peek() == _("else")) {
// else:
wasElse = true;
input.read();
expectToken(input, _(":"));
} else {
parseOper(input, script, PREC_AND);
expectToken(input, _(":"));
script.addInstruction(I_DUP, 1);
script.addInstruction(I_BINARY, I_EQ);
jmp = script.addInstruction(I_JUMP_IF_NOT);
}
script.addInstruction(I_POP);
ExprType type1 = parseOper(input, script, PREC_SET);
type = max(type, type1);
if (wasElse) {
break;
} else {
if (input.peek() == _(",")) input.read(); // optional comma
jmpsEnd.push_back(script.addInstruction(I_JUMP));
script.comeFrom(jmp);
}
t = input.peek();
}
if (!wasElse) {
type = max(type, EXPR_STATEMENT);
script.addInstruction(I_POP);
script.addInstruction(I_PUSH_CONST, script_nil);
}
for (Addr jmp : jmpsEnd) script.comeFrom(jmp);
return type;
} else if (token == _("for")) {
// the loop body should have a net stack effect of 0, but the entire expression of +1
// solution: add all results from the body, start with nil
@@ -565,7 +607,7 @@ ExprType parseExpr(TokenIterator& input, Script& script, Precedence minPrec) {
script.addInstruction(I_BINARY, I_ITERATOR_R); // iterator_range
}
script.addInstruction(I_PUSH_CONST, script_nil); // push nil
unsigned lblStart = script.addInstruction(with_key
Addr lblStart = script.addInstruction(with_key
? I_LOOP_WITH_KEY // lbl_start: loop_with_key lbl_end
: I_LOOP); // lbl_start: loop lbl_end
expectToken(input, _("do")); // do
@@ -713,7 +755,7 @@ ExprType parseOper(TokenIterator& input, Script& script, Precedence minPrec, Ins
// I_JUMP_SC_AND after # if top==false then goto after else pop
// YYY
// after:
unsigned jmpSC = script.addInstruction(I_JUMP_SC_AND);
Addr jmpSC = script.addInstruction(I_JUMP_SC_AND);
parseOper(input, script, PREC_CMP);
script.comeFrom(jmpSC);
}
@@ -725,7 +767,7 @@ ExprType parseOper(TokenIterator& input, Script& script, Precedence minPrec, Ins
parseOper(input, script, PREC_ADD, I_BINARY, I_OR_ELSE);
} else {
// short-circuiting or
unsigned jmpSC = script.addInstruction(I_JUMP_SC_OR);
Addr jmpSC = script.addInstruction(I_JUMP_SC_OR);
parseOper(input, script, PREC_CMP);
script.comeFrom(jmpSC);
}