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expr2c now distinguishes binary and multi-ary expressions #1726

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Merged
merged 1 commit into from
Jan 20, 2018
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expr2c now distinguishes binary and multi-ary expressions #1726

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78 changes: 66 additions & 12 deletions src/ansi-c/expr2c.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -813,10 +813,9 @@ std::string expr2ct::convert_trinary(
if(src.operands().size()!=3)
return convert_norep(src, precedence);

const exprt::operandst &operands=src.operands();
const exprt &op0=operands.front();
const exprt &op1=*(++operands.begin());
const exprt &op2=operands.back();
const exprt &op0=src.op0();
const exprt &op1=src.op1();
const exprt &op2=src.op2();

unsigned p0, p1, p2;

Expand Down Expand Up @@ -1028,6 +1027,61 @@ std::string expr2ct::convert_binary(
const std::string &symbol,
unsigned precedence,
bool full_parentheses)
{
if(src.operands().size()!=2)
return convert_norep(src, precedence);
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Shouldn't that now be a PRECONDITON?

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@kroening Would you mind fixing/commenting on this?

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expr2c has, historically, not enforced any data invariants on expressions; malformed expressions are instead printed as "Lisp" expressions.

Using a PRECONDITION here would be a very substantial change in semantics.


const exprt &op0=src.op0();
const exprt &op1=src.op1();

unsigned p0, p1;

std::string s_op0=convert_with_precedence(op0, p0);
std::string s_op1=convert_with_precedence(op1, p1);

std::string dest;

// In pointer arithmetic, x+(y-z) is unfortunately
// not the same as (x+y)-z, even though + and -
// have the same precedence. We thus add parentheses
// for the case x+(y-z). Similarly, (x*y)/z is not
// the same as x*(y/z), but * and / have the same
// precedence.

bool use_parentheses0=
precedence>p0 ||
(precedence==p0 && full_parentheses) ||
(precedence==p0 && src.id()!=op0.id());

if(use_parentheses0)
dest+='(';
dest+=s_op0;
if(use_parentheses0)
dest+=')';

dest+=' ';
dest+=symbol;
dest+=' ';

bool use_parentheses1=
precedence>p1 ||
(precedence==p1 && full_parentheses) ||
(precedence==p1 && src.id()!=op1.id());

if(use_parentheses1)
dest+='(';
dest+=s_op1;
if(use_parentheses1)
dest+=')';

return dest;
}

std::string expr2ct::convert_multi_ary(
const exprt &src,
const std::string &symbol,
unsigned precedence,
bool full_parentheses)
{
if(src.operands().size()<2)
return convert_norep(src, precedence);
Expand Down Expand Up @@ -3386,7 +3440,7 @@ std::string expr2ct::convert_with_precedence(
precedence=16;

if(src.id()==ID_plus)
return convert_binary(src, "+", precedence=12, false);
return convert_multi_ary(src, "+", precedence=12, false);

else if(src.id()==ID_minus)
return convert_binary(src, "-", precedence=12, true);
Expand Down Expand Up @@ -3690,7 +3744,7 @@ std::string expr2ct::convert_with_precedence(
return convert_unary(src, "~", precedence=15);

else if(src.id()==ID_mult)
return convert_binary(src, "*", precedence=13, false);
return convert_multi_ary(src, "*", precedence=13, false);

else if(src.id()==ID_div)
return convert_binary(src, "/", precedence=13, true);
Expand Down Expand Up @@ -3739,22 +3793,22 @@ std::string expr2ct::convert_with_precedence(
return convert_complex(src, precedence=16);

else if(src.id()==ID_bitand)
return convert_binary(src, "&", precedence=8, false);
return convert_multi_ary(src, "&", precedence=8, false);

else if(src.id()==ID_bitxor)
return convert_binary(src, "^", precedence=7, false);
return convert_multi_ary(src, "^", precedence=7, false);

else if(src.id()==ID_bitor)
return convert_binary(src, "|", precedence=6, false);
return convert_multi_ary(src, "|", precedence=6, false);

else if(src.id()==ID_and)
return convert_binary(src, "&&", precedence=5, false);
return convert_multi_ary(src, "&&", precedence=5, false);

else if(src.id()==ID_or)
return convert_binary(src, "||", precedence=4, false);
return convert_multi_ary(src, "||", precedence=4, false);

else if(src.id()==ID_xor)
return convert_binary(src, "^", precedence=7, false);
return convert_multi_ary(src, "^", precedence=7, false);

else if(src.id()==ID_implies)
return convert_binary(src, "==>", precedence=3, true);
Expand Down
4 changes: 4 additions & 0 deletions src/ansi-c/expr2c_class.h
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,10 @@ class expr2ct
const exprt &src, const std::string &symbol,
unsigned precedence, bool full_parentheses);

std::string convert_multi_ary(
const exprt &src, const std::string &symbol,
unsigned precedence, bool full_parentheses);

std::string convert_cond(
const exprt &src, unsigned precedence);

Expand Down